Transcript for:
Understanding Cellular Respiration and Fermentation

hey everyone Dr D here and in this video I am going to explain cellular respiration as well as fermentation and this is going to be a one-of-a-kind video this is my way of explaining this topic I know it's super complicated and convoluted and it could be one of the harder things to learn in uh biology course so I'm going to do my very best to make it as straightforward as possible and I'm going to explain it in my own unique way that makes sense of it in a story like fashion so you're learning the story of the process so you can make better sense of it so let's go ahead and get started D Dr D Dr D Dr D Dr D Dr D Dr D Dr D Dr D explain stuff so what is cellular respiration this is how our mitochondria produce ATP and it's not just in eukariotic mitochondrion like this one but Pro carots as well can undergo cellular respiration you ever heard in grade school you know cell the the mitochondria is the PowerHouse of the cell you know that cheesy saying okay and why do they why do they say that they say that because uh the mitochondria produces ATP and the mitochondria produces that ATP by using chemical energy that you've consumed in your food right so you ate sugar like this see uh this is glucose C6 h126 this is glucose I'm going to write that down and usually when when when we're discussing cellular respiration we're talking about how glucose is broken down by the mitochondrion to form ATP but just just realize that that you know fats are also broken down via cellular respiration even proteins can be broken down via cellular respiration but we're we're going to look at how glucose we're going to look at how glucose we can use the energy from the glucose molecule to make ATP for the cell remember ATP is the energy currency of the cell anytime the cell wants to do an endergonic process a process that requires energy then the cell can utilize ATP to drive that reaction forward right so the cell constantly needs ATP your body constantly needs ATP and the reason you eat breakfast lunch and dinner the reason why you consume sugars and fats and proteins one big reason is to get chemical energy right the chemical energy that's going to produce that ATP and that process this equation right here this is the equation of cellular respiration this is cellular respiration I'll write that right here cellular respiration okay so cellular respiration let's go over the equation real fast and then I'm going to show you exactly how cellular respiration works so take a look here glucose and six oxygen are required these are the reactants these form 6 CO2 this is a product this is CO2 carbon dioxide product and six water this is also a product okay uh they form six CO2 six water and either 30 net ATP in UK carots or 32 net ATP for pro carots I'll explain why later on but so from one glucose molecule from one glucose molecule we are able to get in US UK carots we can get 30 ATP molecules right and and then our body can use that ATP to do things that need energy to work in the cell okay but the story all starts in the mitochondrian so take a look here this is a mitochondria and what I need you to remember before I start my story are the parts of the mitochondrion right so remember this let's just do a review of the cells chapter remember cells chapter we have an outer membrane outer membrane this is the outer membrane of the mitochondria see what I drew here on the right this is an animal cell remember animal cells have a nucleus and then they have various mitochondria inside they can have dozens of mitochondrion this is one mitochondrion that's why it ends an on right but you would have numerous m mondria and I'm just showing you a mitochondrion has an outer membrane and what's this membrane do you remember what this membrane is right here that's right Wicket it is the inner membrane the inner membrane okay and let me ask you this what's this what's this space in the middle called what's that fluid in the middle called do you remember that's called The Matrix remember that the Matrix and this one's tough what was the space called you see that space between the outer membrane and the inner membrane that tiny bit of space between the outer membrane and the inner membrane of the mitochondrion yes this little space is called the inter membrane space okay I just need you to remember that because I'm going to show you what we're going to do next okay bear with me I know it seems convoluted it's it's going to be a long story but I promise you if you follow me step by step you will understand this I want you to understand this and I want you to not just memorize things but I want you to really get it okay so we're going to do that together what I'm going to draw next is I'm going to zoom in okay I'm going to zoom in on this part of the membrane I'm going to zoom in on that part of the membrane and I'm going to magically make this part of the membrane pop up on that board there you go so I have now zoomed in what I'm trying to show you let's get our bearings real quick what I want you to understand is that I'm zooming in on this little box right here looking at these two membranes of the mitochondria right do you remember what was this membrane called the bigger membrane that's right Wicket the outer membrane so this is the outer membrane this right here is a phospholipid Bayer it's the out outer membrane of the mitochondria okay so this here is I'm just going to write o m for outer membrane of the mitochondria which would make this membrane the inner membrane I'll write I am for inner membrane of the mitochondria again what was the tiny bit of space called between the two membranes you got it Wick it the intermembrane space this is your inter me membrane space remember this is the tiny bit of space between the outer membrane and the inner membrane of the mitochondria all right now let's think about this if this is the outer membrane that's the inner membrane what's this space represent if we were to zoom in on this box right here into the mitochondria this area right here would represent what part can you beat Wicket hopefully you beat wicket but Wicked is right this is the Matrix this is the Matrix of the mitochondria so this is the Matrix of the mitochondria this represents the inner membrane of the mitochondria this space represents the intermembrane space of the mitochondria this membrane represents the outer membrane of the mitochondria and then what would be this out here what what do you think that is if you said cytoplasm this is the Cy plasm of the cell right outside of the outer membrane is the cytoplasm of the cell so this represents the cytoplasm of the cell okay of the eukaryotic cell okay so hopefully we have our bearings at this moment now I'm going to be doing some erasing so if you're following along if you're trying to draw this out I I recommend that you use pencil and eraser or color pencils that can be erased cuz I'll be doing some erasing as I explain what's happening in the mitochondria like how the mitochondria is making ATP so let me introduce you to a very special enzyme okay it's a membrane enzyme complex and do you know where it lives it lives in the inner membrane of the mitochondria see I'm going to do a little erasing here like I said and I'm going to draw a special membrane enzyme this guy right here I'm drawing him in purple okay there you go now what is this thing I drew in the inner membrane of the mitochondria this is an amazing enzyme it's a amazing machine and I want to explain it to you because it will blow your mind it actually this enzyme is a transmembrane remember transmembrane means it spans the entire membrane it's a trans membrane enzyme and the enzyme enzymatic activity that it does is that it can take a DP remember what ADP stands for adenosine D phosphate and it can also take a pi do you guys remember what pi stands for inorganic phosphate and guess what it can do with the two this enzyme can actually combine the two it actually combines ADP with P or inorganic phosphate what do you think it makes when it combines ADP and P that's right Wicket it makes a TP okay it makes ATP no exclamation mark necessary but it makes ATP and this is an amazing enzyme that makes ATP and actually do you remember how many ATP are made during cellular respiration from a single glucose what can you tell me from a single glucose we can make either 30 net ATP for UK carots or 32 net ATP and pro carots well guess what 28 of those 30 or 32 are made right here by this special enzyme so I'm going to name this enzyme for you now this enzyme is called ATP ATP synthace synth Ace do you know what that stands for remember enzymes end in Ace so this is the ATP synthesizing enzyme ATP synthes and its job is to live as a transmembrane protein and you can find them in the inner membrane of the mitochondria see this the folded chiste of the inner membrane of the mitochondria is littered with these ATP syntheses there isn't just one there's the thousands upon thousands upon thousands of these ATP synthes in the inner membrane of the mitochondria in fact the inner membrane in the mitochondria is highly folded because you have to have tons of space for as many of these ATP synthes as possible Right there'll be tons and tons of them and what are they all doing they're all making ATP and how do they do it how do they make ATP they combine ADP and P to make ATP Isn't that cool so this is why it's called ATP synthes now what let me let me ask Wicket let me ask Wicket Wicked what are you curious about about this enzyme let me ask you Wicket and let me ask you at home do you at home think that ATP synthes is just making ATP spontaneously remember what spontaneous meant it meant energetically for free it meant without any energy input right let's see let's see you got it Wick it making ATP is not free is it breaking ATP if you break ATP into ADP andp that releases a bunch of energy right that's spontaneous so do you think the opposite making ATP do you think what ATP synthes is doing making 28 ATP for every glucose molecule that it's energetically favorable that it's spontaneous and it's just doing this for free no right so what I'm trying to get at is that something must be powering ATP synthes right something must be making it work okay and here's some here's something I'll tell you about ATP synthes it's so cool listen to this listen to this you see the top part I drew here the top part of ATP synthes literally spins okay everyone look at this this top part literally spins if you look at ATP synthes it has a top portion that can rotate and it kind looks kind of something like this okay from your textbook it looks it looks something like this and this top portion right here it can rotate okay and look the bottom portion here it can produce ATP all right and so let me ask you this do you think this top portion can just spontaneously Spin and pop out ATP no right no something is driving the top portion to spin and yes this is a rotary motor isn't that neat um you know um it's the world's smallest motor the top part literally spins so that the bottom part can make ATP isn't that neat so if if the top part doesn't spin the bottom part doesn't make ATP so something must be driving the top part to spin do you get where I'm going with this something is causing the top part to spin and I usually ask students to answer what do you think is driving the top part to spin I'll give you a second to come up with a with a idea what do you think is driving the top part to spin and providing the energy so that the bottom part can make ATP no you're actually wrong you guys this is the first time Wicket has ever been wrong he must have been slacking this week Wicket it's not ATP it's actually something else isn't that neat ATP is not what's driving ATP synthes to spin actually something else is let me let me share with you what let me let me share with you well it turns out that out here are a bunch of protons do you guys remember what protons are let me let me do an aside real quick do you remember what a proton is a proton is H+ do you remember that H+ means proton H+ means proton hydrogen ions are protons and that means that a hydrogen a hydrogen is simply a proton with an Associated electron remember that this is important to remember there's a reason I reminding you about this electron so a hydrogen atom is a proton with an electron a hydrogen ion is simply the proton the electron went away okay well it turns out there's a bunch of uh protons out here in the intermembrane space look at this I'm going to draw a bunch of H+ in this little space look there are a bunch of H+ in fact I'm what I'm going to do is this watch I'm going to draw brackets around one of these H+ and I'm going to put a arrow up showing you there's a high concent contion of protons okay there's a high concentration of protons in the intermembrane space and the Matrix remember this is the Matrix down here the Matrix has protons as well but the concentration of protons is lower so there are protons here but there are just aren't nearly as many right it's not as concentrated I should say so low concentration of protons on this side of the membrane in The Matrix High concentration of protons on this side of the membrane in the intermembrane space so now let me ask you this do these protons if they're highly concentrated in this little space do these protons want to diffuse into the Matrix where there's a lower concentration of protons I'll give you a second to think about that you have totally redeemed yourself Wicket yes the protons want to diffuse back in right but let me ask you this if you've been paying attention over the last few se uh few chapters if you've been paying attention let me ask you this can protons which have a charge can they diffuse directly through a membrane to the other side via simple diffusion no they can't right because they're charged right charged entities charged substances like protons they can't diffuse F across a membrane but that's where ATP synthes comes in you guys look at this ATP synthes the reason the top part spins is because it allows protons to stick the protons will stick to the top part and then the protons actually force their way in and they they actually cause the spinning and then the protons force their way into the Matrix isn't that neat so just like just like the Hoover Dam you know if if you've ever heard about the Hoover Dam there's water that flows from the top part you know the higher level of water through the dam to the lower part of the water um the lower water level and that drives turbines that spin okay this is based on not gravity right but on diffusion the protons the protons are forcing their way in because there's a high concentration of protons in the intermembrane space the proton force their way into the Matrix they can't go through the membrane directly but but they can go through ATP synthes you know why because ATP synthes serves as a carrier protein remember carrier Transporters ATP synthes will allow the protons to get to the other side but at a cost right the cost is spinning the ATP synthes kind of like you know if you're at the airport and they have those rotary doors you know those revolving doors how does the revolving door work let's say it's a it's not a automatic one well you have to come up to the revolving door and you have to push on that revolving door right and that causes the revolving door to turn right and the revolving door turns but it's because you're pushing on the revolving door right does that make sense well this is this rotary part of the ATP synthese it turns but the only reason it turns is because the protons are pushing like people pushing out of the airport turning that door right so as long as the protons are diffusing in the top part spins it has power it's powered to spin and that's what's providing the energy to make ATP remember energy coupling I said that an extonic process can release the energy required for an endergonic process well here the extonic process is the diffusion of protons and the end Gonic process that it's powering is the formation of ATP 28 ATP and this is known as ATP synthesis and this is why this enzyme is known as ATP synthes now a little bit of terminology for you guys I know I I'm beating you up I've gotten a lot of information across but believe me there's a lot more to cover in cellular respiration but if you're ever confused hit stop go back listen to it again draw it out you can do it you know this is going to be tough the first time you may have to listen to it a couple times but I promise you you'll get there now I said diffusion of protons across a membrane right diffusion of protons did you know that has a name associated with it that name is I'm going to write it here for you diffusion of protons it's termed Ki Kimi osmosis Kimi osmosis is the diffusion of protons that's what's powering ATP synthese to spin and to produce ATP okay now here's another terminology I need to know I need you to know okay the when the protons when the protons undergo chem osmosis that don't they exert a force like as the as the protons are diffusing in aren't they producing a force that's causing this rotary part of ATP synthes to spin right well that Force has a name okay I know it's getting tricky that Force the force that's causing ATP synthes to spin is called pmf pmf for proton proton motive motive Force okay so think about it this way chem osmosis diffusion of protons across a membrane exerts a force that force is called the proton motive force or pmf for short that's the energy that's being provided to spin ATP synthes so that it's powered up to produce ATP let me put it this way if those protons weren't forcing their way in with chemiosmosis exerting a proton motive Force then ATP synthes the top wouldn't be spinning and and the bottom would not be producing right it would not be making any ATP okay so now let's turn our attention to the next thing I hope everyone's up to speed again again let's just recap ATP synthes an important transmembrane protein complex enzyme that exists in the inner membrane of the mitochondria actually there's thousands of these guys in the inner membrane of the mitochondria in those chist right now the top part of ATP synthes spins to power the bottom part to make ATP okay and the reason the top part was spinning remember was because of proton flow right protons diffusing across the membrane process known as chem osmosis exerting a proton motive Force now let me ask you let me ask Wicket Wicket what do you think if we're if if we're trying to understand this process what question pops into your head as as the next logical thing to ask about how this process works what do you think Wicket what do you guys curious about at home like like what is the next thing that you'd want to know in order to understand this process let's see what Wicket says okay that that's great Wicket Wick's asking Wick's asking well H how how is there so many protons out here do you see this you guys there are there's a high concentration of protons in this intermembrane space you see this and there's a lower concentration of protons on this side if this was a closed system do you remember what would happen all these protons would flow in or at least uh half of these protons would flow in until there's an equal concentration of protons on both sides and let me ask you this if if all the protons squeezed in and there was a equal concentration of protons on both sides of this membrane would ATP synthes still be spinning that's right that's right Wicket no it would not spin so let so so here's what I'm getting at you guys something must be keeping the proton concentration high in the intermembrane space it's not like you were born right it's not like you were born with with an infinite amount of protons in the in in the intermembrane space and they just over time squeeze their way uh you know into the Matrix spinning ATP synthes forever right something must be pumping protons into the intermembrane space something must be adding the protons in the intermembrane space does that make sense so let's do some more erasing all right you guys ready to erase I'm going to erase a chunk here and a chunk here and a little chunk here and a chunk here okay so I'm doing a little bit of erasing and now I want to grab a blue marker all right you ready to draw some other parts here there's more parts to this setup here all right ready there's this guy okay I'm drawing this transmembrane protein complex here's a different transmembrane protein complex here's a different integral membrane protein complex but not transmembrane look how it this one doesn't span the entire membrane like the other guys do and here's another one this is another transmembrane protein complex all right so you see what I drew here all right all right these are called complex one this is complex one 2 three and four okay now let me just tell you what they do first and then I'll give you more information later okay guess what these guys do complex one three and four are actually proton pumps proton pumps what do you think proton pumps do they pump protons it wasn't a trick question they pump protons so look look at what look at what pump one does this is called this is pump one it takes protons from The Matrix and it pumps them into the intermembrane space you see that it's a one-way pump pump three same thing it takes protons from The Matrix and it pumps them into the intermembrane space what do you think pump 4 does it's not a trick question it pumps protons into the intermembrane space you see that there are three pumps that live in the inner membrane of the mitochondria and by the way you know there's thousands of pump one there's thousands of pump three pump four and there's thousands of this guy too which I'll tell you what he does later all right but let me ask you this let me ask you this if there are three pumps pumps one three and four and their job is to pump protons they pump protons into the intermembrane space and that's their job would it make sense then why we have a high concentration of protons in the intermembrane space CU they're pumping those protons faster than the protons are diffusing back in right so think about that real quick just think about it there's three pumps pumping protons into the intermembrane space that's what's resulting in the high proton concentration of the intermembrane space and the relatively low concentration of protons in The Matrix of the mitochondria and that's what keeps ATP synthes working right so as long as these pumps are pumping okay as long as these pumps are pumping there should be plenty of protons out here to chemo most exert that proton motive Force keep ATP synthes spinning to make ATP did you get that but now let me ask you the next question here let me ask Wicket Wicket what would be your next logical question about this process about how it works what's yours at home I like that question Wiki all right Wicket just asked if this is active transport of protons what do you think at home is this active transport of protons by these pumps or is this passive transport of these protons look what's happening these protons are being pumped from an area of low concentration to an area of high concentration of protons that's active transport isn't it doesn't active transport need to be powered by something okay so doesn't that mean pumps 1 3 and four need to be powered what do you think Powers pumps one three and four can you be Wicked to the answer no this is the second time Wicket has ever been wrong okay Wicket you can't keep saying ATP it's not ATP usually it's ATP okay you guys at home yes usually when the professor asks what's powering this process or that process and the cell the answer is ATP but actually it's not ATP in this case it wasn't ATP for the for what's powering ATP synthes and it's not ATP for what's powering these pumps it's something entirely different so let me explain that next all right so how do these pumps work to understand I drew some purple Dots here and what I want you to know is that these purple dots represent Co factors usually they contain iron or some other co-actor but that's not important what's important is that you understand what these dots do each of these purple dots can accept an electron and then pass the electron on that's their job right so what you should know is do you remember the concept of electro negativity do you remember that concept that different uh different elements have different uh Co different affinity for electrons and that's called electro negativity well here what you should know is that the electr negativity of this co-actor here is the lowest right this dot right here on complex one has the lowest electro negativity and the one next to it has a higher electro negativity and the one next to that has a higher electro negativity higher higher higher higher higher higher higher highest okay so these dots accept electrons and can pass the electrons on and these dots span they range from low electro negativity on complex one to high electro negativity on complex 4 okay so let me ask you this let me let me let me uh let me give you an example this is an example I give my students sometimes you know um if you go up to a soda machine and you feed coins into that soda machine those coins go on a journey right those coins kind of go on a journey into the vending machine right if you want a soda or you want to buy a can of Pepsi or something those those coins go on a journey just like those coins go on a journey um you can feed electrons into this machine this whole this whole complex forms a machine electrons can be added here okay electron coins can be added here at complex one or here at complex 2 okay so you can feed this machine electrons and so just like you can add coins to a vending machine you can add you can think of it as electron coins right this is an electron coin this is an electron coin you can add electrons to this machine you can add them either here at at complex one onto this co-actor or at complex 2 at this co-actor what do you think happens next let me ask you that if I give this co-actor an electron and its neighbor let's say this neighbor is greedier than this one what do you think happens next what do you think Wicket right the neighbor's greedier for the electron so it'll steal the electron you see that so I fed the machine an electron here its neighbor is more electronegative and it took the electron its neighbor is more electronegative so what do you think's going to happen next that's right the electron will hop here and then the electron will hop here right and and what if I fed the machine here well this is where this electron would begin its Journey its neighbor would steal the electron its neighbor would steal steal steal do you see how these electron are going on a journey and why do you think they're going from dot to dot well remember because this final dot right here this co-actor is the greediest one it's it's the one with the highest electro negativity the highest affinity for electrons your book may actually call this standard reduction potential your book may not refer to it as standard reduction potential but just in case your book does that's what it means on the left you have low standard reduction potential and on the right you have high standard reduction potential that's the same way of saying low electro negativity High electro negativity if complex one is low in electro negativity well then complex 2 is going to steal its electrons then complex 3 which is even more electronegative is going to steal those electrons and then complex 4 is going to steal those electrons so that's how it works right imagine a piano right imagine a piano and each key of the piano from left to right is more and more magnetic right a stronger and stronger magnet so if I have a piano the key on the left would be the least magnetic then the one right next to it would be more magnetic and then next to it would be more magnetic what would happen if I put a steel ball on the left key and let go what do you guys think would happen what do you think would happen if I put a steel ball on a piano key on the left wouldn't it Z to the right wouldn't that steel ball zip to the right right that's exactly what's Happening Here you guys so but not with magnetism obviously but with electro negativity I'm feeding this machine electrons the electrons are going on this journey and they end here on complex 4 I can feed the electrons here and it goes on the journey or I can feed the electrons here and it goes on a journey and let me ask you this is this a spontaneous Journey for these electrons are these electrons zipping on their own or is something forcing them to go Wicket has it right these electrons are spontaneously zipping through the you know system from complex one or two all the way through complex 4 these electrons are moving spontaneously it's driven by electr negativity right so just like if I put that that Ste ball on the on the magnetic keyboard and it zips off to the right because the right key the right key is the most magnetic if I put these electron coins in the machine they will zip to the right because this you know because of electr negativity your neighbors keep stealing you right so um this is a spontaneous flow of electrons what I'm trying to get at is this do you guys remember energy coupling right energy coupling this means that you can use the energy from a spontaneous process to power a non-spontaneous process you remember that so look the fact that the electrons are spontaneously moving through this process right the electrons are moving through the all these complexes that's spontaneous that means it's exergonic that means it releases energy and that's the energy that's being being used to do what to pump to actively pump the protons so let me ask you again this is active pumping of protons isn't it aren't these pumps pumping protons actively does active transport require energy where's the energy coming from think about it can you beat Wicket from the electron flow Wicket you you got it you've totally redeemed yourself at this point the electrons are flowing the electrons are flowing that's what's providing the spontaneous energy that's what's providing the energy to pump the protons isn't that neat the energy released from flow of electrons is being used to actively pump the protons isn't that neat so I hope that makes sense this is how this complex works and now let me let me name it I haven't given it a name yet have I let's do this so now let me give you the name of complex one 2 3 and four together they have a name I don't just call this complex 1 2 3 and four I call it the electron transport chain the electron transport chain chain you may have heard of this before shortened EC so when I say the ETC I mean the electron transport chain and that's now you I hope you understand the the role of this little guy right he's not a pump is he uh complex 2 of the electron transport chain is not a pump is he but isn't he required as you know part of the wire per se you know why I call this a wire you know how wires work and electricity you know electrons are used to propel you know electricity electrons flow through a wire right well here this is almost like a biological wire isn't that neat this is electricity isn't it electrons flowing through a biological wire Isn't that cool to think about it that way so the electron transport chain is this complex I've just been talking about but let me tell you something before we take a quick quick little break time with Gizmo and Wicket and see what they're up to let me tell you something I personally don't like that name for this complex you know electron transport chain I really don't like that name and I'll tell you why because look at what it's called it's called the electron transport chain that M that makes it sound like its job its job the job of complex 1 2 3 and four is to transport electrons do you think that's its job or or do you think that's how you power it Wick it you're on top of it that's just how you power it right but what's the job let me ask you this what's the job of the electron transport chain is it to transport electrons or is it to transport protons that's right it's main job look at you guys its main job is to pump these protons actively you see look at this the main job of the ETC is to actively pump the protons so that you have a high concentration of protons so that they can chem Osmos provide a proton motive Force to spin ATP synthes to make ATP right that's the job of the electron transport chain so if I was naming this thing I would call it the proton transport chain okay I would call it the proton transport chain because that's its job you know it's like calling a car a gas guzzler sure it guzzles gas but that's not its job you know it's an automobile right so you know um calling this complex 1 2 3 and four an electron transport chain is akin to calling a car a gas guzzler does it guzzle gas sure but is that its main job no it's a side effect of doing its job it's it's a necessary evil of doing its job right so the electrons flow sure but that's what powers these pumps to pump the protons so I can make ATP all right you guys ready for break time with Gizmo and [Music] Wicket all right now here's something important that you need to understand I told you that you can add electron coins to this machine and what do those electrons do once I add them to the machine that's right they ZIP down from purple dot to purple dot right these are co-actors from co-actor to co-actor and then they come to a rest here the the electron ends here right the electron is now stuck on the last co-actor on complex 4 well let me tell you something very important you guys here's here's the thing I need a way of removing that electron from this final dot right I need to get the electron off the ride so think about it this way if I if you're at you know uh Disneyland and you're on a roller coaster when you go on a ride you need to get off the ride at the end right if you can't if you don't get off the ride at the end then other people can't go down the ride does that make sense so think of it like the freeway you know uh if people aren't exiting the freeway well then pretty soon it gets all jammed up you know like a traffic jam and the whole thing kind of shuts down right like your favorite freeway in your city okay so so if I can't take this electron off the ride at the end of his ride then more electrons can't come down the ride because it it just gets you know like the electron gets stuck here then the next one gets stuck here right and then the next one gets stuck here and the next one gets stuck here and soon they're all you know they all have electrons and and there's no more no more electrons that can join the ride right so we need a way of getting off the ride so we need a molecule that is very electr negative that likes electrons right that means electr negative to steal the electrons from this dot if you're going to steal the electrons from this co-actor right here you need to be pretty electronegative yourself right because remember complex 4 this is a very Electro negative complex so if you're going to steal from complex 4 you'd best be pretty Electro negative yourself and look at look at the equation I want you to look at the equation for cellular respiration what on what what what what up there is very electronegative oxygen great oxygen oxygen is highly electronegative remember oxygen appears at the top right of the periodic table of elements and this means that it's a highly electr negative element so that's exactly what happens watch this oxygen oxygen comes along and do you know what your textbook refers to it as not just O2 not just O2 but 1 12 O2 you know what 1/ 12 O2 means half of an oxygen molecule so half of an O2 which essentially means what n o and oxygen and oxygen comes along and it actually picks up that electron actually it could pick up two electrons as well as two of these protons two protons and what do you think that forms if one oxygen picks up two electrons and two protons and remember a proton and an electron is a hydrogen and one oxygen picked up two electrons and two protons what did it form can you beat wicket if formed water H2O isn't that neat so look at this oxygen comes along at the end of the ride at the end of the electron transport chain or Etc oxygen comes along and it picks up two electrons from the ride as well as two protons from The Matrix to form what to form water okay to form water oxygen picked up electrons to form water now because of Oxygen's role as the final acceptor of the electrons it has a special name I need you to remember this terminology this name okay oxygen is known as the terminal terminal which means final terminal electron acceptor the terminal electron acceptor also sometimes called the te a the terminal electron acceptor it's called the terminal electron acceptor because it picks up the electrons at the end right isn't that neat and here's something else that's more neat okay since you've been born you've had to Breathe Right since you were a baby you were just born you've breathed in right you know breathing in nice and relaxing but necessary for life right have you ever wondered why you need to breathe no really seriously everyone knows you have to breathe right and I ask my students all the time why do you need to breathe they say to stay alive well why what's what's in the air that you need to breathe they say what oxygen right oxygen and and then I say why do you need oxygen then the answer is invariably to stay alive okay but no one knows any deeper than that unless you've studied science unless you've studied cellular respiration let me ask you now now that I've explained some things to you let me ask you now why do we need to breathe why do we breathe in oxygen that's right because we need someone to take the electrons off the ride okay we need a ter electron acceptor we need something that's highly electronegative oxygen checks that box we need something that's highly electr negative to pick up the electrons at the end of the ride at the end of the electron transport chain and by removing those electrons from the electron transport chain we make more room for more electron coins to come in and go ZIP down the the train right so so this electron can add and it goes down the ride and then it gets picked up by oxygen and then this electron goes down the ride and it gets picked up by another oxygen and and and I can keep feeding this vending machine coins I can keep feeding it electrons I keep feeding it more and more electrons because I know Oxygen's on the other side picking up those electrons allowing me to feed more machines but let me ask you this let me ask you this what would happen if I ran out of oxygen H what would happen if I ran out of oxygen yeah exactly that wouldn't be good right because if I ran out of oxygen the electrons wouldn't have a way of leaving this ride which means this the electrons would back up right on this machine the electrons would back up like a traffic jam and this whole thing would shut down and that's that's by the way some foreshadowing that's how we Branch into fermentation which I'll explain later on but but as long as we have oxygen and we're breathing nicely we should be just fine and this machine works just fine all right you guys I hope you're following along try to think of this as a story with try to use a flow of thoughts okay and just try to imagine everything we learned from the beginning right what's going on in the mitochondria ATP synthes it's powered by protons at the electron transport chain pumps those protons all right so let's take a let's let's take a little step back at this point and look at the equation look at the equation for cellular respiration what have we discussed so far haven't we discussed oxygen haven't we discussed oxygen and what happens to oxygen during this process remember oxygen picks up electrons to form water right so oxygen became the product water now let me ask you this this is important do you all remember the definitions of oxidized and reduced remember Leo says G remember that uh that that uh pneumonic device I had you learn let me ask you and let me see if you can beat Wicket during this process of cellular respiration is oxygen getting oxidized to water or is oxygen getting reduced to water I need you to think about that that's right Wicket you got it Wicket got it it's reduced remember when you're talking about the terms oxidized and reduced you really need to know those terms for to understand cellular respiration because that's all cellular respiration is by the way a series of what's called Redux reactions reduction and oxidation that's what Redux stands for and that's all cellular respiration really is okay so remember what what I told you to remember that little story of the Leo says G Leo L EO Leo like a lion says G right g r Leo stands for loss of electrons as oxidized g means gain of electrons is reduced right what is oxygen doing at the end of the ride oxygen is picking up electrons right so is oxygen gaining electrons to become water that means oxygen is getting reduced to water so here you can say oxygen oxygen becomes reduced you should know that during cellular respiration oxygen your terminal electron acceptor is getting reduced to water the product okay and again I can't stress to you how cool this is you guys now you finally know why you've been breathing your whole life this is literally the reason you're breathing in you know when you were born and you needed to breathe okay this is why this is why the cellular respiration is why because students ask all the time why do we have to learn this convoluted thing you know with all these parts and this electron transport chain they top synthes and protons and what in the world you know um but it's vital it's literally vital that you understand this you know why I say literally vital because you you you know that's your vitals your vitals include are you breathing right so breathing in oxygen your whole life the reason for that has been you need oxygen as a terminal electron acceptor to pick up the electrons so the oxygen gets what the oxygen gets reduced to water that's why you breathe that's why you need oxygen okay that's literally why you breathe so let's say you want to be a doctor in the future or a nurse in the future or any science scientist or clinical person or even if you want to know why people breathe right you need to know your cellular respiration that's how important this topic is it's not just it's not just there to you know stress you out with how convoluted it is it's there because it's vital it's very important that you understand you know how it works you know if you want to go in anything medicine related you should explain why you know you need oxygen to live and this is why people need oxygen to live so this is vital to understand in more than one way right no pun intended actually pun's intended all right so let's keep going let's keep going so we have explained so far we have explained so far why oxygen is required it's your terminal electronic acceptor which gets reduced to water okay great but we have not explained the role of glucose and we have not explained explained the role of CO2 or you know and we have explained 28 of these ATP but not all of them okay so we still got some things to explain right so let's let's turn our attention now to glucose I want you to take a look at glucose glucose has several hydrogen atoms on it it has several hydrogens and so do fats do you know fats we learned about fats here's a picture of a fat okay remember fats have these long fatty acid Tails these three long fatty acid tails and what are those Tails just full of just just clamoring with tons and tons of hydrogens right so fats have hydrogens on the Tails sugars like glucose have hydrogens and so why why do I keep talking about hydrogens well that's because this is what we need this is why these are energ molecules sugar has energy because of its hydrogens fats have a lot of energy because of the hydrogens proteins have a little bit less energy and it's because they're lacking a lot of those hydrogens right but it's these hydrogens I want to talk about let me ask you this look at this remember what did I say over there what is a hydrogen what is a hydrogen atom remember a hydrogen is simply a proton a proton what's another way of writing proton H+ hanging out with what a hydrogen is a proton hanging out with an electron that's all a hydrogen is isn't it a hydrogen is a proton hanging out with an electron and believe it or not this is why sugars and fats are so full of energy because let me ask you this real quick I just taught you this process here you see this here all this stuff going on what powers this whole machine what powers the machine isn't this whole thing powered by electrons and protons think about it electrons flowing Powers protons pumping which then result in ATP so do you agree that it's nothing more than electrons and protons that power this powerful machine of the electron transport chain plus ATP synthes that's all you need to power this machine to give you this awesome amount of ATP 28 ATP per glucose now look at this sugars and fats are chalk full chalk full of hydrogens hydrogens have the protons and the electrons necessary to power the powerful machine you put you put in two and two together what gives you more energy what gives you more energy sugars or fats think about that can you beat Wicked that's right Wicket fats right fats why do you think fats give you so much more energy than sugar based on your understanding that hydrogens power this machine Wick it you're on top of it it's because fats have so many hydrogens on those fatty acid tails that each one of those hydrogens you know what you want to do with those little hydrogens those yummy little hydrogens you want to pluck them off yep you know and feed them into the machine so that's what we do you guys that's how cellular respiration works you take sugars or fats you take sugars or fats and you pluck each hydrogen off so what I want to do with glucose you know what I want to do with glucose I want to pluck each and every one of these hydrogen off of glucose and I want to I want to take it over to the machine so I can power the machine I can feed the electrons through the electron transport chain and the protons can get pumped Pumped out right you see what I'm saying you you follow me what I want to do is take sugars and fats I want to take the hydrogens and I want to feed the hydrogens into the machine that's how I'm going to power the machine now let me ask you this let me ask you this if I were to take all the hydrogens away from glucose right C6 h126 if I were to take all the hydrogens away what's left just take a look I want all the hydrogens to feed into the machine if I take all the hydrogens over to the machine what's left CO2 so do you see what happens here I I take all the hydrogens away from glucose and all that's left are C's and O's and that forms my product CO2 isn't that interesting isn't that interesting isn't that interesting that's why CO2 is a product that's why CO2 is a product because when I take glucose and I remove all the hydrogens because I want to feed the hydrogens into this machine to power the machine all that's left of my glucose glucose are the C's and the O's CO2 okay now let me ask you this if I take H's away and remember H's also contain electrons right if I take the hes away from glucose have I reduced glucose to CO2 or have I oxidized glucose to CO2 think about that think about that can you beat Wicket that's right Wicket I have oxidized oxidized remember oxidized is Leo loss of electrons means oxidized I have removed hydrogens that means each hydrogen contained an electron I have removed electrons from from glucose so I have oxidized you see here look I have oxidized glucose to CO2 I have oxidized glucose to CO2 and very important that you understand that during the process of cellular respiration glucose is oxidized to CO2 while oxygen is reduced to water very important for you to understand that and this is and how does your body here think about this when you breathe in you mostly want what you want oxygen right and why do you need oxygen when you breathe in to live right yeah like to live but why do you really need oxygen when you breathe in based on what we just learned because you need the terminal electron acceptor right oxygen gets reduced to water great but let me ask you this when you breathe out what do you breathe out a high concentration of you know this right what do you breathe out more than you breathed in everyone knows you breathe out CO2 right you guys know that why do you breathe out so much CO2 well think about it what's left of your glucose after I've oxidized the glucose what's left of glucose CO2 so that CO2 leaves my cells it gets into my blood it goes to my lungs and I breathe out the co CO2 so isn't that interesting the reason you've breathed in since you were born is because you need oxygen as a terminal electron acceptor and the reason you've been breathing out so much CO2 since you've been born is because that's what's left of your glucose and your fat molecules after you have fully oxidized them right that you've broken them down with cellular respiration so I'm going to blow your mind again real quick if you don't mind you know unless you mind getting your mind blown right but I'm going to blow your mind again and I'm going to tell you that when you lose weight you know um you know when you exercise when you exercise and you lose weight let's say you've been exercising for a month and you've lost a couple pounds right you've lost some weight you lost two three pounds you know you've been exercising that month and you've been trying to be good about your diet you know and you've lost lost a little bit of weight so you're trying to get in shape right where did that weight go right you ever thought like where did that weight go did it disappear did I sweat it out did I poop it out you know did I pee it out you know sorry to be a little gross there but you know where did it go right people don't know most people don't know well believe it or not a majority of that weight left your body through your mouth through your mouth through breathing out isn't that neat think about it think about it look at this weren't these the sugars that were weighing down your body sugars weighing down your body and after you've oxidized it what's left CO2 which leaves your body how by breathing it out and what about fats remember fats when you break down fats what's left of the fat also CO2 right also CO2 so those fats that are weighing down your body right those fats that make up your you know that that fill up your fat cells right those fats that are causing you to not like the number on the scale sometimes right um those those fats leave your body as CO2 as well so when you lose weight you're losing the majority of your body's weight just by breathing out okay and now don't try just sitting there and breathing really fast doesn't that doesn't work I know what you're thinking like what if I just sat here and breathe really fast would I lose a bunch of weight like actually that doesn't work at all right cuz you know all you're doing then is sucking in air and blowing out the same air your body has to produce more carbon dioxide right how could you get your body to produce more carbon dioxide well you would have to exercise right because when you exercise when you exercise your body needs more ATP you know to to keep going right cuz ATP Powers your cells correct so when you're exercising your body needs more ATP what's the only way to get more ATP faster well it's to break down more sugar and more fats and use more oxygen this is why you start breathing so hard when you exercise you start breathing really hard you need more oxygen uh to burn more sugar and more fat faster right and then when you blow out when you exhale you actually exhale much more CO2 than you normally do right and to couple that with a diet why do you diet if you want to lose weight why do you diet well it's to make sure that you have fewer sugars and fats to burn so do you see why do you see why diet and exercise go hand in hand for losing weight because with with exercise you're converting more sugars and fats to ATP CO2 and water CO2 which you breathe out and with dieting with dieting you have fewer glucose and fats to burn so by having fewer fats to burn and burning them faster you're going to Exhale more CO2 right than the amount of you know sugars and fats you consume so why do I say all this well because some of you want to study nutrition or you want to go into um exercise physiology you cannot understand nutrition you cannot understand exercise exercise physiology any of this stuff without understanding cellular respiration because if you don't fully understand cellular respiration you don't understand how weight actually leaves your body right through CO2 you don't understand how diet and exercise exerise truly work unless you understand cellular respiration so I you know when students ask you know why do we have to learn cellular respiration it seems kind of kind of archaic and boring well remember if you want to be a competent uh person in medicine you want to explain to a patient why they're breathing you want to explain to a patient why they're breathing out CO2 you want to explain to a patient the benefits of diet and exercise and why they're important and how people gain weight or lose weight you cannot competently do that without understanding cellular respiration isn't that neat so let's keep going all right at this point I have a kind of a confession what I've been doing so far is explaining cellular respiration backwards I said at the beginning of this video that I have my own special way of explaining cellular respiration and this is the way I've come up with this is the way I've been teaching cellular respiration for over 10 years now and it's backwards I start with the end of the story and I work my way towards the beginning of the story because it's just easier to understand this way okay everything I've explained so far remember everything I've explained so far includes these the the electron transport chain complex 1 2 3 and four ATP synthes which spins and makes ATP all this stuff right here which which the electron transport chain plus uh ATP synthes chem osmosis this is called oxidative oxidative phosphorilation phosphorilation okay oxidative phosphorilation that's the process I have spent some time explaining to you on the board and guess what cellular respiration has three major phases and this is phase three okay this is phase three so you now understand phase three of cellular respiration but guess what there is two and a half two and a half other phases okay there's phase one phase one which is called glycolysis glycolysis there's phase 1.5 okay this is Phase 1 and a half and Phase 1 and a half is called oxidation oxidation of pyruvate and then there's phase two phase two is called the citric acid cycle also known known as the Krebs Krebs cycle also known as the TCA cycle your textbook may call may call Phase 2 the citric acid cycle or it could call it the Krab cycle or the TCA cycle don't get confused they all mean the same thing I think our current book Campbell's 12th uses uh citric acid cycle so that's what I'm going to be going with but remember citric acid cycle is the same as crab cycle or TCA cycle so now you might be you know you might feel deflated you may feel like oh my gosh like wait all this explanation with all these colors on this board which it looks convoluted you know all this stuff was just part three you know and it's true but there's a reason I start with part three and I just want to share that with you now okay look at this part three is so important right you see how ATP synthes works and how many ATP did ATP syn make 28 for every glucose right so look 28 of these 30 net ATP are made right here 28 of these net ATP are made right here so that's the most important part of the cellular respiration is ATP synthes making this Lion Share of ATP 90% of the ATP you know the 28 ATP the the rest of these phases you see glycolysis oxidation of pyate citric acid cycle these these don't make tons of ATP okay uh in fact look glycolysis gives you a whopping 2 ATP okay glycolysis gives you a whopping two net ATP and the citric acid cycle gives you a whopping two net ATP okay so you get two ATP here during glycolysis you get two ATP here in the citric acid cycle but who cares that's not nothing compared to the 28 ATP that's made here right and by the way let me tell you something real quick okay I I forgot to define something the ATP that's made by ATP synthes with the help of oxygen during oxidative phosphorilation this ATP is made by what they call oxos or oxidative phosphorilation so if if if if a exam question asks by what process does ATP synthes make ATP this is the 28 ATP that are made here were made by oxidative phosphorilation that's the process by which these ATP were made any ATP made during oxidative phosphorilation this process by ATP synthes those 28 ATP were made by what's called oxidative phosphorilation which means that these two ATP and these two ATP are not produced by oxidative phosphorilation they are produced by something called substrate level substrate level phosphorilation which I'll explain in a bit and this these two ATP were also made by substrate level phosphorilation okay great now again the Lion Share of ATP is made at the very end by ATP synthes and a pit amount is made during the citric acid cycle and glycolysis so let me ask you this if you've been been paying attention Okay you I know you've been paying attention at home I know Wick's been paying attention unless he's napping let me ask you this what do you think is the main point of glycolysis oxidation of pyate and citric acid cycle what do you think is the main point of those steps if it's not directly to make ATP then what do you think those steps focus on what happens during those steps just use logic and reasoning right just use logic and reasoning what do you think is going on during those early phases glycolysis oxidation of pyate citric acid cycle think about that can you beat Wicket Wick's about to chime in here that's right Wicket the whole point is to oxidize glucose now let me tell you something look at this remember what did I say what did I say is the main point of you know cellular respiration to make ATP using what look glucose what do we want from the glucose what do we want from the glucose do we want its carbons it's hydrogens or its oxygens to power this machine which one do we want we want these hydrogens right well let me tell you something taking 12 hydrogens from a glucose molecule is not easy you can't just take all 12 of these hydrogens in one step okay if you could if let me put it this way if you could take if you could take these 12 hydrogens from glucose in one step and get them all to the you know to the electron transport chain and get them all to the final step in one step then there wouldn't be a phase one a phase 1.5 and a phase two CU you know why it turns out it takes many different steps remember metabolic process takes many enzymes right there's a metabolic process that takes many many steps right well it it turns out it takes a lot of steps and a lot of enzymes to fully oxidize glucose to CO2 to take each and every one of these hydrogens away from glucose and get those hydrogens over to the electron transport chain does that make sense and that's the whole purpose that's the whole reason you have glycolysis that's the whole reason you have oxidation of pyate that's the whole reason you have the citric acid cycle is to fully oxidize your glucose so you're during glycolysis you start with glucose right you start with glucose you start with glucose and what did I say you're left with at the end of cellular respiration your glucose gets fully ox oiz to CO2 so by the end of the citric acid cycle by the end of the citric acid cycle all that's left of your glucose is CO2 okay so you have fully oxidized your glucose and and here's the thing what you want to do is take the H's you want to take the H's from glucose and you want to feed them to the machine and here's how you do it there are two electron carriers they're called nad+ and F A these are electron carriers this is what nad+ looks like it's a d nucleotide you don't need to know this for my class but uh NAD stands for nicotinamide adenosine dinucleotide here you can see the molecule it's a dinucleotide and here it is in its oxidized form okay and what NAD does what NAD plus does is it comes over here to one of these early steps it picks up two electrons it picks up two electrons and a proton okay it picks up two electrons and a proton to become what to become nadh and then it delivers that H to the electron transport chain it gives the H to the electron transport chain nadh gives its H to complex one its electron goes through complex one its proton pops off and it it's one of the protons that gets pumped across the membrane another thing that's another another of these electron carriers is fad fad can pick up two electrons and two protons and fad gets reduced to fadh2 which then goes and drops off its electrons at complex 2 okay so here's here's I I know it's a little confusing but here's how it works during glycolysis oxidation of and citric acid cycle right oxidation of py and citric acid cycle during these steps H's are taken from the sugar and handed to the electron carriers either nad+ or fad these carriers once they pick up those H's they get reduced to their reduced form right so nad+ picks up some H's to become nadh fad picks up some H's to become fadh2 and those H's track travel to the electron transport chain and they and nadh visits complex one right it's what feeds the coins the electron coins into complex one while fadh2 visits complex 2 and it feeds its little electron coins into complex 2 right and those are the electrons that ZIP down the electron transport chain to be picked up by oxygen at the end right to to pump the protons to power the ATP synthes isn't that neat so the H's the H's on glucose the H's on glucose are given to either nad+ or fad that reduces these oxidized carriers to the reduced form the carriers then carry that's why they're called electron carriers they're called electron carriers because they carry the electrons from glucose to the electron transport chain and I know that's kind of a misnomer too because students ask but they're carrying h they're not carrying electrons but remember electrons are part of a hydrogen sure sure NAD picked up two electrons and a proton and fad picked up two electrons and two protons so so technically they're hydrogen carriers and if I if I could rename these guys I would call NAD plus and fad hydrogen carriers because what they're really doing is taking hydrogen from the sugar and carrying those hydrogens to the the electron transport chain nadh drops off the hydrogen here fadh2 drops off the hydrogen here but they call them electron carriers because the more important cargo is actually the electrons because the electrons are what's powering the electron transport chain the protons are just getting kind of Pumped across but they would kind of be there anyway okay so that's why they're called electron carriers but if I were to rename them I would call them hydrogen carriers right but these are the two electron carriers so this is the whole point you guys right listen to this this is the whole point of steps one one and a half and two during glycolysis you're going to take your glucose and you're going to steal some of its hes right you're going to steal some of those H's and when you steal those hes you're going to give them to NAD plus you're going to you're going to create two nadh's right that means you you have given some of those hydrogens to nad+ reducing it to nadh okay and where do you think where do you think nadh goes once it's created right so I stole some H's from glucose okay and now I have nadh well the nadh travels to the complex one to drop off the H you see what happens and when it drops soft that H it becomes nad+ again and it can come back and pick up more electrons from another glucose molecule so that's what these carriers do during glycolysis glucose gives a couple of H's to nad+ uh making nadh nadh books it over to the electron transport chain it feeds the electrons into the electron transport chain and the protons get pumped okay and then NAD plus is reformed it comes back it picks up more electrons and does it over and over again okay and and that's great because that that's going to power these pumps to pump the protons to make ATP does that make sense that's the important part of what's Happening Here and then at the end of glycolysis we have you know we haven't fully stolen all the H's we have not fully stolen all the hes okay in fact here is exactly what's happening during glycolysis so here we can see an overview of aerobic cellular respiration remember stage one is called glycolysis and we're going to delve into that in just a second glycolysis uh is first stage followed by stage 1 and A2 remember stage 1 and A2 is pyrovate oxidation next we have stage two the citric acid cycle also known as the kreb cycle also known as the TCA cycle and then lastly remember on the board all that explaining I did that was oxidative phosphorilation which includes the electron transport chain as well as chemiosmosis through ATP synthes so this I love this slide you may want to take a picture of this or screen grab of this because this is a awesome slide that shows a a big picture overview of all of cellular respiration and here you can see all the steps laid out I just want to show you something again before I delve into glycolysis in detail I just want to show you something look how glycolysis is the only one of the steps that occurs in the cytool the liquid portion of the cytoplasm you see this glycolysis occurs in the cytool OR cytoplas ASM the rest of the steps the rest of these steps occur inside of the mitochondria all right so that's one thing to understand and again remember glycolysis is the first phase of this process and we're going to go into that in detail this is a process where glucose is processed into two molecules of pyrovate we also produce two nadh and two net ATP and that ATP was formed by substrate level phosphorilation which I'll explain more in just a second so next let's delve into glycolysis and again one more big picture overview before we delve into the details of glycolysis during glycolysis the input is mainly glucose which is then processed through glycolysis in into two molecules of pyate two net ATP and two nadh now let me show you step by step how this process works all right so here you can see the process of glycolysis it's a number of steps as you can see this is a metabolic pathway with several steps now what I'm going to do is I'm going to explain each step in more detail than you really need so don't get bogged down in the details because I'm going through details so that you can see step by step what's going on but I'm not going to need you to know every little step okay first I'm going to explain it in great detail then I'll let you know what you need to remember right for for the exam okay so let's start at the top here let's start here okay these are the first steps okay let's start at the top here these are the first steps to glycolysis and remember glycolysis occurs in the cytoplasm right of the cell and so you start here with What's called the investment phase it's called the investment phase because we are going to invest to ATP molecules so let me show you how this works all right so again this is the invest phase of glycolysis which of course happens in the cytoplasm you start with a molecule of glucose and look at this pink structure here this pink structure has six carbons 1 2 3 4 5 six these six carbons represent the six carbons of glucose but obviously glucose isn't just a chain of six carbons right they didn't draw the whole carbon molecule they just drew the six carbons okay but remember this is C6 h126 now the first thing that happens to glucose is that an ATP comes along and the ATP gives one of its phosphate groups to glucose so you see if ATP gives a phosphate group to glucose glucose has the phosphate group and ATP is missing one of its phosphate groups it becomes ADP this process is known as phosphorilation when a phosphate group is added to a molecule this molecule is phosphorilated so now you have a phosphorilated form of glucose called glucose 6 phosphate why because it's it's still glucose but the sixth carbon has a phosphate group attached do you see how that works next there's an isomerization that occurs where glucose gets its bonds rearranged into fructose right fructose is an isomer of glucose so glucose was isomerized to fructose so now it's known as fructose 6 phosphate next that that type of Step happens again where another ATP comes along and this ATP also phosphorites fructose 6 phosphate so now you have fructose with two phosphates because each of these ATP donated a phosphate group to the to the sugar and now this is a doubly phosphor ated sugar right so now it's called fructose six bis phosphate fructose this is the sugar fructose it has a it has a phosphate on the first and the sixth carbon that's why it's called bis phosphate that means two phosphates okay so do you see why sorry do you see why this is known as the investment phase of glycolysis because two ATP were invested two ATP were used up to get the ball rolling this primes the pumps this allows the the subsequent steps to happen Okay so this is known as the investment phase we have invested to ATP to get to this point so here this is now the payoff phase what happens is look up here do you remember where we left off we were talking about fructose 16 bis phosphate well now the Lis part of glycolysis occurs do you guys know what glycolysis means glyco refers to sugar or glucose what do you think Lis refers to remember hemolysis or lysis what does lysis mean remember lysis means break so what we're about to do is break the sugar in half you see right here we're going to break the sugar in half into two okay so now we've broken the six carbon sugar into two that then both of these both of these are called glycer alahh three phosphate that means it's a three carbon sugar called glycer alahh with a phos phosphate on the third carbon and here's one glycer alahh 3 phosphate from this half of the fructose and here's the other glycer aldhy 3 phosphate from the other half so what have we done we have taken a single six carbon sugar and we've chopped it in half one half goes down this column the other half goes down this other identical column so whatever happens whatever happens down this column is mirrored in this column because we have two three carbon sugars now not just one six carbon sugar right now at this point remember what do we want from these from these sugars remember what I said at the board what do we really want from these sugars what's the yummy component of these sugars that we want to harvest do you recall that's right Wicket we want hydrogens right so we're going to capture some of the Hy hydrogens from these sugars and we're going to transfer those hydrogens to the electron carriers remember nad+ uh nad+ will pick up two electrons and a proton and become reduced to nadh and so will the identical pathway on the right uh nad+ will pick up two electrons and a proton and become reduced to nadh now let me ask you this let me ask you this and see if you were paying attention ear at the board what do you think these nadh do at this point this nadh right here and this nadh right here what do you think they do once they are formed once they have captured those yummy hydrogens from the sugar what do you think they do that's right they head right over to the ETC anytime anytime you see nadh formed anytime you see nadh formed it makes its way right to the electron transport chain okay and it drops off those electrons at the uh electron transport chain and nadh remember it drops off its electrons at complex one of the electron transport chain so at this point the sugar has been oxidized right the sugar has lost electrons right the sugar has been oxidized and it's picked up another phosphate group and it's picked up another phosphate group so now what you have are two of these molecules here this molecule here it's called 13 bisphosphoglycerate it is a three carbon sugar with two phosphate groups one on the first carbon and one on the third carbon and remember you have two of these you have one here and you have like one over here right so because whatever is happening to this glycerate is happening to that one now here is the payoff phase okay remember you made an invest M of 2 ATP but now we are going to pay off that investment that investment's about to pay off all right so how do we do this this is a process known as substrate level phosphorilation let me show you how it works if we make ATP by taking a phosphate group like this one see the phosphate group attached to a substrate such as a sugar or organic molecule we're going to transfer look we're going to transfer this phosphate group from this glycerate phosphoglycerate we're going to transfer that phosphate group to ADP what do you think would happen if I transfer this phosphate group to ADP well that ADP becomes ATP and so we've just formed ATP but this is known as forming ATP by substrate level phosphorilation this means that the way we made the ATP was by getting a phosphate group from a substrate from a organic molecule like this so anytime you see like a substrate like an organic molecule that has a phosphate group and that phosphate group is transferred to an ADP to make an ATP that ATP was made via substrate level phosphorilation so how many ATP have we made at this step right here we have made two see we've made an ATP here and we've made an ATP here so didn't we just earn back our investment didn't we just earn back you know we we invested two ATP at the beginning those ATP phosphorilated our sugar and now we gave it back right we gave the phosphate back to ADP to make ATP and we just made two ATP back we've invested to ATP and we made 2 ATP back okay and then at this point we still have a phosphate group group on both of our sugars so we move that phosphate group around and then we give the last phosphate group to an ADP again with substrate level phosphorilation to make ATP again so we actually make two more ATP okay so how many ATP did we invest two how many ATP did we get back four so let me ask you this how did how many ATP do we net net means come out ahead like profit right if you invest two and you get back four your net is actually two because you're up two right okay does that make sense so we say that during um glycolysis we net 2 ATP right and we formed two nadh but let me ask you this after your poor glucose has been manipulated and chopped in half and changed around do you think it's still called glucose no at the end of glycolysis you're going to end up with remember with two three carbon sugars right two three carbon molecules these three carbon molecules are called pyruvate or pyruvic acid depending on your textbook right and again how many of these pyruvate do you have at the end of glycolysis how many of these three carbon sugars should you have two of them right remember one down each of these Pathways cuz a six carbon glucose got broken into two three carbon sugars and now you have two pyrovate molecules so again I don't need you to remember each and every little step okay of glycolysis you may need to learn every single step if you're going to go off to like let's say med school and you're going to study for the mcats there might be some technical questions in there but for the most part in my class and many other classes you really don't need to know every little tiny step but I I explain every step so that you can see kind of what's going on with this metabolic pathway but what I really want you to know are just the general things like for example um where does glycolysis occur uh let's go back to this helpful slide where does glycolysis occur the cytool or cytoplasm great how many net ATP did we get two by what process substrate level phosphor relation how many nadh were formed two and where did those nadh go once they were formed look at this white Arrow I like this figure see look at this look at this white Arrow it's showing you that the two nadh that were formed by glycolysis are going where look at follow the the white Arrow it's headed to the electron transport chain remember to drop off that hydrogen cargo to drop off those electrons at the electron transport chain the electron transport chain is going to be powered by this H it's going to be powered by these two electrons that are being carried by nadh does that make sense so again what do you need to know you need to know glycolysis occurs in the cytool and you should know the inputs and outputs so glycolysis uh breaks down glucose into two pyrovate molecules two ATP and 2 nadh all right welcome back so now you know exactly what's happening during glycolysis and remember by the end of glycolysis your six carbon glucose has now been broken down into two three carbon pyrates right well those pyrates still have hydrogens for us to steal those two two pyrates are headed towards oxidation of pyrovate and here oxidation of pyrovate is going to take those two pyruvates it's going to take these two pyruvates and this is what it's going to do all right yes it is time for step one and a half remember at the end of glycolysis you formed two pyrovate molecules right two pyrovate three carbon molecules of pyrovate now watch both of these pyruvate head into the mitochondria the pyrovate head into the mitochondria and during this step is this is the step known as pyruvate oxidation also known as oxidation of pyrovate either way it means the same thing so let's explore what happens during pyruvate oxidation here all right so remember at this Point your pyruvate is heading from the cytool into the mitochondrion and did you only have one pyrovate or two that's right Wicket you have two pyrates right so you have two pyrates two three carbon molecules see one two three two of these three carbon pyrates are heading into the mitochondrion and here's what happens as it goes through when the pyate enters the mitochondrion it gets oxidized right so a couple of its hydrogens are taken away from it and given to nad+ reducing nad+ to nadh so again pyrovate is oxidized so that nad+ can be reduced to nadh remember NAD Plus picks up electrons so it's reduced and what happens once this nadh is formed where does it go once it's formed remember that's right it heads off to the electron transport chain anytime you see nadh form like this it's got the H cargo it's ready to go to the electron transport chain and drop off that those electrons right now as a consequence a carbon a carbon you see this carbon there's pyrovate was a three carbon molecule uh you see this carbon right here and these two oxygens well they get cleaved okay during this process the carbon and two oxygens are cleaved as carbon dioxide and they leave the cell as carbon dioxide by the way this is some of the carbon dioxide that you breathe out this becomes carbon dioxide that you you know exhale so now if if that happened if you lost one of your three carbons then how many carbons do you have left over on each of your pyrovate two right so now look this this is a two carbon molecule your your three carbon pyrovate is now a two carbon uh molecule um uh now this this twocc carbon molecule picks up a co-enzyme do you guys remember what a co-enzyme is it's an organic co-actor this co-enzyme is called co-enzyme a and this organic co-actor is added on and here's the organic co-actor called uh co-enzyme a so the resulting molecule has two original carbons as well as this co-enzyme a it's called ACL COA and again I want you to I want you to multiply everything here by two right because again did you start with one p Pate or two at the end of glycolysis two pyrates that means that in this step you form two co2's two nadhs which head to the electron transport chain and you form two AAL coas two acial coas are left over right again during this step what was this step called oxidation of pyate two pyrovate enter the mitochondrion two CO2 are formed two DH are formed and two AAL COI are left over uh let's go back to our nice little overall sheet here this summary sheet and check it out again look at I this is why I love this summary sheet look at this two pyrovate enter the mitochondrion and become Tu ailo in the meantime two nadh are formed which go where follow the white arrows they go to the electron transport chain to drop off those H's um two CO2 are formed remember um look at uh you started with glucose which is a six carbon molecule well two of those carbons just left as CO2 all right and what's left over acial COA at this point you have two acial coas left over this is what's left of your original glucose molecule your original glucose molecule is now two acial coas and those acial coas are on their way to the citric acid cycle for further oxidation now welcome back now you know that during oxidation of pyrovate this half step two pyrates are broken down into two acial COA along the way remember two nadh are formed and two CO2 CO2 is going to leave your body as you know air and then the two pyrates are broken down into sleo and you have formed two nadh right where did the nadh go that are formed during this step that's right they're going to go to complex one to drop off their electrons okay and what do we have left two AAL coas now these two acid coas they still have yummy hydrogens right they still have hydrogens for us to feed on okay those two a COA are headed to the next step the citric acid cycle aka the Krab cycle aka the TC a cycle and here is how that cycle works so at this point pyruvate oxidation has been completed two pyrovate have been converted into two acial COA and remember both of those acial COA molecules are headed for the citric acid cycle also known as the Krab cycle also known as the TCA cycle all right so let's go into detail about this cycle during this cycle you're going to see and again I'm going to break it down step by step for you but you're going to see that during this cycle we are going to oxidize our acial COA we are going to get six nadh formed two fadh2s four co2's and two ATP via substrate level phosphorilation but let's go break it down step by step and so we understand it fully all right here it is the citric acid cycle check it out here at the top you have a CLE COA entering the cycle all right and this is a metabolic cycle now real quick before I get started with this cycle I want to ask you how many acial COA did we have at the end of the previous cycle was it just one acid COA or did we have two that's right Wicket we had two acial COA that's awesome so because remember our glucose was processed into two pyrates and then those two pyrates were converted into two acial coas so remember this is what I need you to understand this is showing you in this figure here you're see what's happening to one of the acial coas but if you want to know what's happening overall you have to understand that you're going to get two rounds of the of the citric acid cycle because you have two AAL coas and this cycle is simply showing you what's happening to one of the two so you have to multiply everything here by two to get the full picture okay so just with that in mind these two acid coas are going to enter the AC citric acid cycle okay but what happens to each ACL COA now watch this okay I want to show you something very interesting when you look at a biochemical cycle like this you see how it's a cycle a a biochemical cycle is called a cycle because the thing that's made at the end what's made at the end here I'm circling it you see this guy right here this is called oxal acetate or oxelo acidic acid sometimes your textbook might call it that but this is oxaloacetate and this is the organic molecule that needs to be replenished it it gets replenished replenished means remade at the end of the citric acid cycle and why is that so important well because the thing that's made at the end of the cycle is needed to start the cycle again that's what a biochemical cycle is the product of the cycle is needed to start the next cycle so what happens let me show you something neat your ACI COA which has two original carbons from your glucose as well as this co-enzyme a this acyoa enters the cycle and it joins forces with oxyacetate so literally they get bound together so oxaloacetate this organic molecule binds coal to aetl COA and in this process you lose the co-enzyme a coenzyme a comes off and now you've actually combined aetl COA with oxaloacetate and now you have this Mega molecule here well it's not so Mega but you get the picture it's a bigger molecule isn't it because this is what's left of OSL COA and this is what's left of oxaloacetate this is a big molecule called citrate and by the way I'm going to tell you something really neat and interesting just now citrate is another word for citric acid right citrate is citric acid and this is why this is called the citric acid cycle because the very first thing you do is actually make some citric acid by combining what acylcoa with oxaloacetate so one thing I do want my students to know I do want you to know is what needs to be replenished at the end of the citric acid cycle the answer would be oxyacetate and to make citric acid very interesting right now just to take a step back what do you think we want from this citrate molecule at this point what do you think we want to harvest from this citrate molecule eventually what do you think think about it what do we want from citrate that's right Wick it we want hydrogens remember there are nice yummy hydrogens for us to collect and hand to the electron carriers so let's see how that works citrate is going to be converted to isoc citrate next a very important step happens isocitrate is going to get oxidized which means we're going to take some of its electrons away in the form of hydrogens so we're going to give those hydrogens to nad+ reducing na D plus to nadh this results in one of these carbons you see this carbon right here and those two oxygen well those leave as CO2 so one of the carbons one of the two carbons that entered the cycle has just left as CO2 so there's only one carbon left right cuz look two carbons entered one carbon left right and once you form this nadh where does the nadh go where does this nadh go once it's formed that's right Wicket it's going to book it over to the electron transport chain that's anytime nadh is formed it just makes its way over to the electron transport chain to drop off that H to drop off those electrons to power the electron transport chain and return in the form of nad+ to do it again it just shuttles back and forth right so now after we've oxidized isocitrate and isocitrate has lost one of its carbons as carbon dioxide isocitrate is now converted to alpha ketoglutarate alpha ketoglutarate is this molecule right here and look what do we want from this molecule right here don't let Wick it beat you what do we want from this molecule right here do you think that's right Wicket we want hydrogens so we're going to take more hydrogen so we're going to hand it to nad+ reducing it to nadh this is going to cause this this carbon and those two oxygens to leave as CO2 so at this point how many carbons entered on a CLE COA how many carbons entered two and at this point how many carbons have left two so we shouldn't be losing any more carbons we have officially run out of carbons on our glucose molecule okay very interesting stuff so let's take a look here and see uh what happened our Alpha ketoglutarate was oxidized to uh suol COA uh the reason it has a COA by the way you don't need obviously you don't need to know a lot of this stuff but the another co-enzyme a has been ad added to Alpha ketoglutarate and so uh what's left is suoo and now what's really interesting is this dance that occurs where a phosphate group an inorganic phosphate is transferred to suoo and then that phosphate group is transferred to GDP phosphor corating gddp to GTP and then GTP phosphor relates ADP to make ATP so all that to be said we just made an ATP molecule via substrate level phosphorilation we we we we moved a phosphate group around from organic molecule to organic molecule and that's why this is known as substrate level phosphorilation and we just made an ATP and in the process our sual COA is now known as su8 because it loses is that co-enzyme a and succinate is then further oxidized we take more of its hydrogens away but this time we give it to a different carrier right we give two hydrogens to f a fad picks up two hydrogens to form fadh2 and where do you think fadh2 goes with that cargo that hydrogen cargo it goes to the electron transport chain exactly succinate becomes uh oxidized to fate fate gets modified to malate and what what do we want finally we want to pick the final carcass clean of hydrogens so we're going to again we're going to oxidize malate we're going to give those electrons to nad+ reducing uh nad+ to nadh where do you think nadh goes that's right it goes over to the electron transport chain to drop off that H and malet is now oxidized to oxy acid which can start the cycle again now I know that was a a mouthful but what does it all mean you don't need to memorize each and every little step unless you're studying for the mcats or in some kind of advanced biochemistry but for a general biology course you don't need to know every little baby step here I don't I don't expect you to know that but I like to explain it so you can kind of visualize and see what's going on remember two carbons entered two two carbons entered two carbons left a bunch of hydrogens were stolen and given to electron carriers these nadh and fadh2 which all go to the electron transport chain remember nadh visits complex one of the electron transport chain fadh2 visits complex two of the electron transport chain dropping off that cargo and then coming back for more uh ATP was formed by substrate level phosphorilation and remember aelo acetate was reformed at the end now now let me ask you this this is only for one turn this is only for one turn of the citric acid cycle but what if I asked you for every glucose molecule what are the products of the citric acid cycle well remember it's everything you see here times two because you had two acial COA not one so if you have two a COA you actually get two rounds of the citric acid cycle which means you form one 2 3 * 2 6 nadh 1 * 2 2 fadh2 2 ATP and how many co2's how many co2's 2 * 2 so four co2's okay and remember what needs to be replenished at the end oxaloacetate so let's go back to our overview sheet real quick and see if everything checks out look at our overview sheet again I love this overview sheet look two acetal COA go into the citric acid cycle and how many nadh are produced six how many fadh2 are produced two and where do they go they go to the electron transport chain to drop off the electrons how many CO2 are formed four how many ATP are made two by substrate level phosphorilation and what needs to be replenished oxaloacetate must be replenished here at the end of the cycle you see how beautiful that is at this point your glucose your original glucose molecule which was six carbons long uh has fully been oxidized to CO2 those six carbons of glucose two of them left the system here as CO2 and the other four left the system here as CO2 as well okay and all of the hydrogens from the glucose you can think of the hydrogens look you see this H here on these two nadh you see these H's here on these two nadh you see these H's and these H's here those were the H's from glucose does that make sense the H's went to the carriers to the electron transport chain the C's and the O's left as CO2 isn't that beautiful so you have fully oxidized glucose its hydrogens were transferred to electron carriers and taken to the electron transport chain and ultimately ended up on water remember at the end of the oxidative phosphorilation oxidative phosphorilation include the electron transport chain and chemiosmosis remember nadh and fadh2 from the previous steps that's what power ERS the electron transport chain to make the 28 ATP via oxidative phosphorilation what was the terminal electron acceptor remember the terminal electron acceptor was oxygen which became reduced to water you see oxygen picks up the electrons at the end of the ride to produce water so this is a beautiful process by which electrons began on glucose they were transferred to the carriers nadh and fadh2 which trans transferred those electrons to the electron transport chain so they would flow from complex one or two through to complex 4 they were then picked up by oxygen and those electrons ended up on water the electrons started on glucose and they ended on water isn't that neat all right did you get all that we're back you know so now you know that your two acial COA entered the citric acid cycle giving you two rounds of the citric acid cycle right not just one round of the citric acid cycle two rounds of the citric acid cycle and remember during that during those two rounds you form six nadh two fadh2 which by the way what do these do remember the 6 nadh go to complex one to drop off those H's where do the 2 fadh2 Go ah yeah they go to complex 2 to drop off the H's to drop off the electrons and what happens to the CO2 the four co2's you breathe them out and you made some you know couple of ATP here so that's great I guess right um so so that's there now have we fully oxidized our uh glucose yes at this point we have fully oxidized glucose look at this we started with C6 h126 during glycolysis we stole some of those H's during pyate oxidation we stole a couple more H's and two of our six look two of our six carbons left two of our six carbons left as CO2 during oxidation of pyate and the other four carbons left during the citric acid cycle so think about it we started with six carbons on glucose and all six of those carbons leave at as CO2 from our breath that's that's what happens we have fully by the end of the citric acid cycle we have fully oxidized glucose to CO2 and we have formed six total CO2 which makes sense because we started with six carbons on glucose so real quick just a review uh glucose is a high energy molecule so is fat and that's because it has all these yummy hydrogens these hydrogens contain the electrons necessary and the protons to power the electron transport chain so we need to take these H's during glycolysis we take some of those H's to make 2 nadh which makes its way to the electron transport chain feeding those electrons into the electron transport chain during oxidation of pyate we take a couple more H's make a couple more nadh so that we can uh transport those H's to the electron transport chain during citric acid cycle we take a bunch of H's we take we make six nadh 2 fadh2 so that we can feed those into the electron transport chain so do you see what's happening here we have been oxidizing glucose we oxidize glucose so that we can reduce nad+ to nadh or fad to fadh2 so we're transferring H's from glucose to the carriers and then those carriers are transporting those H's to the electron transport chain and then those electrons are being picked up by oxygen to form water so did you see what happened I just want to make this clear before we move on I want to make this clear can we follow the Journey of the electrons here remember when I said cellular respiration is just a series of Redux reactions reduction oxidation reduction oxidation I just want to drive this home real quick for you the electrons started on glucose right you see the I'm just going to talk about the electrons instead of the H's okay the electrons started on glucose or fat okay the electrons are handed to either NAD Plus or fad during one of these three processes when those electrons are given to the carriers they become the reduced form of the carriers right they have the hes they have the electron cargo those electrons then go to the electron transport chain nadh hands its electrons to complex one F A 2 gives its electrons to complex 2 those electrons go from complex to complex right you see those electrons hop from complex to complex co-actor to co-actor and who picks up the electrons at the end of the ride that's right the terminal electron acceptor oxygen picks up the electrons to form water did you see how this is the story of a of a a traveling electron right the electrons begin on glucose the electrons are transferred to the carriers and by the way the enzymes the enzymes that transfer electrons to the carriers are called dehydrogenase enzymes in Cas in case you're curious so the electrons started on glucose the electrons were transferred to the electron carriers either nad+ or fad they were reduced to F nadh or fad H2 the electrons visit complex one or complex 2 the electrons flow from complex to complex the electrons are then picked up by oxygen to form water so isn't that neat the electrons went from glucose to carrier to electron transport chain to oxygen to make water that was the full traveling uh uh schematic there that's how that's that's that was the Journey of the electron right so you can think of cellular respiration as kind of the story of a journey of electrons right and because of this journey of electrons this Powers this powerful pump system to pump protons those protons then Kosmos exerting a proton motive for spinning ATP synthes to make the Lion Share 28 ATP 28 ATP so in this next little clip I'm going to explain to you why 28 plus four plus two plus two gives you 30 net ATP in UK carots whereas 32 net ATP and pro carots I'm going to explain that next so to answer why UK carots net only 308p while Pro carots net 32 ATP it all comes down to this step right here both UK carots and pro carots make 2 ATP here during glycolysis via substrate level phosphorilation they make 2 ATP here during citric acid cycle with substrate level phosphorilation and they make 28 ATP here at oxidative phosphorilation you know during the the final step here with ATP synthes 28 so 28 + 2 + 2 is 32 ATP So Pro carots get to keep all 3 to ATP um however in UK carots you see this step here you see how pyrovate needs to enter the mitochondrion well that is an type of active transport and it requires 2 ATP to be used right so so to get the two pyrovate into the mitochondrion we need to invest to ATP so if we're making 32 but we have to use two to get pyate into the Mito andreon then in in essence we didn't really net 32 we netted 30 and do pro carots have a mitochondrion do pro carots have a mitochondrion no remember uh procaryotes don't have mitochondrion so procaryotes they get to keep these two these two and these 28 they don't need to spend ATP to get pyrovate into the mitochondrion because they don't have a mitochondrion all these steps occur in the cytoplasm I hope that makes sense so for the last part of this lecture I want to tell you about these Concepts the important concepts of the difference between aerobic respiration also known as aerobic cellular respiration anerobic respiration or Anor robic cellular respiration and fermentation one thing I want you to know up front is that all of these are separate Concepts right anerobic respiration is not aerobic respiration fermentation is not anerobic respiration each one is an individually different concept and I just want to drive home first of all let's let's just explain the difference between aerobic respiration and anerobic respiration okay so what I've been explaining this whole time of glycolysis oxidation of pyate citric acid cycle and oxidative uh oxidative phosphorilation these three and a half steps these three and a half steps that I've spent this time explaining where I said that oxygen is the terminal electron acceptor of the of the complex four of the electron transport chain this is known as aerobic respiration aerobic respiration oxygen is your te E A it's your terminal electron acceptor it's the one that picks up the electrons at the end of the ride okay and that's what uh aerobic respiration means by the way what does respiration mean when you hear the term respiration or cellular respiration I want you to know this anytime you see a term called respiration like aerobic respiration or anerobic respiration when you see the word spelled out respiration respiration what you need to know is that this involves glycolysis plus oxidation of pyrovate plus citric acid cycle plus uh the the oxidative phosphorilation which includes all this stuff electron transport chain ATP synthes everything you see here everything you see here is respiration right so aerobic respiration means everything you see here and your termin electron acceptor is oxygen but what's anerobic respiration then what's anerobic respiration this is where my students can kind of get confused at times they'll say you know anerobic respiration is without oxygen you know because anerobic means without oxygen but that's not that's that's okay but that's only a fraction of the of the definition the fraction of the explanation so what is anerobic respiration that means that this is happening but without oxygen right without oxygen but didn't I tell you didn't I tell you something okay think about this real quick didn't I tell you that if there's no Oxygen then this shuts down and that's true this whole thing shuts down if this shuts down if this shuts down is that still respiration cuz remember what did I tell you respiration is respiration means glycolysis is working oxidation of pyrovate is working citric acid cycle is working Ox oxidative phosphorilation is working these are all working so if I just took away oxygen that wouldn't be respiration would it um this would shut down and everything you know everything except glycolysis would shut down by the way did you know did you know that if I run out of terminal electron acceptor everything shuts down except glycolysis we'll get to that we'll get to that but what's anerobic respiration how can I do all of this let me ask Wicket let me ask you to think about this for a second I just want you to think for a second and I'm going to ask Wicket to answer too hopefully you can beat him to the punch how can I do all of this without oxygen how can I do all of this without oxygen if I just took oxygen away well then it would shut down right but how would I do all of this without oxygen what did you say Wicket Wicket is a genius you guys Wicket is saying that what if something else besides oxygen will served as our terminal electron acceptor such as reduced sulfate s so42 minus right so you know a a molecule other than oxygen serves as the ter terminal electron acceptor then if this other molecule were to pick up the electrons well would that would that uh work would that work okay think about that if I used a different electr negative molecule to pick up the electrons at the end of the ride would the ride shut down no the ride would keep going right so that's what I want you to know that's what I want you to understand in anerobic respiration glycolysis still works oxidation of pyate Works citric acid cycle works and oxidative phosphorilation works but the only difference is what the only difference is that instead of oxygen being our terminal electron acceptor that picks up the elect r at the end of the ride some other molecule that's electronegative such as reduced sulfate is our terminal electron acceptor does that make sense so it's a molecule other than oxygen that serves as the terminal electron acceptor now let me ask you this do you think that humans humans like you and me are capable of anerobic respiration that's right Wicket we are not but let me tell you this we aren't the only creatures on the planet there are some procaryotes bacteria ARA and did you know there are some creatures that don't breathe oxygen at all they breathe something like sulfate right so you know if you've ever seen those Sulfur Springs where it's like hot and bubbly Sulfur Springs well there's creatures living in there and they're breathing not oxygen they're breathing sulfur so they're breathing something like sulfate so humans what you should know is that humans are not capable of anerobic respiration it's impossible that would mean that we breathe something other than oxygen no we are aerobic respirators does that make sense we breathe oxygen okay uh we can't switch to breathing sulfate if if oxygen becomes unavailable right but there are some creatures that Brea breathe sulfate or nitrate right or something else right so these creatures breathe something other than oxygen they use something other than oxygen as their terminal electron acceptor so the electron transport chain never shuts down is that neat so you should know that the only the only difference between aerobic and anerobic respiration that I need you to know about is that the terminal electron acceptor is different right it's a different molecule and humans are not capable of anerobic respiration at all all right so you might be wondering well Dr D what in the world is fermentation then all right so I'm going to explain fermentation fermentation I want you to know this because students mess this up all the time okay you guys fermentation is not anerobic respiration you hear me fermentation is not anerobic respiration they are not the same thing remember anerobic respiration means everything here is working great except your terminal electron acceptor is something other than an oxygen okay that's not what's going on in fermentation let me explain fermentation okay look at this what was our terminal electron acceptor for us humans and cats wicket okay oxygen right oxygen and what did oxygen become reduced to to water right okay during this process now let's say let's say you and I we you know decide to run a marathon and you know I'm uh let's say a couch potato I'm not you know I'm not usually running at that all that much right so I'm not I'm not training for this Marathon but let's say I want to go run a marathon the first thing that's going to happen after a couple miles is I'm going to just start breathing really really hard you know why because suddenly I'm exercising and my body is trying to produce a bunch of ATP to keep me going okay to keep my body going I need to produce more ATP this means that I'm going to burn more sugars and fats but what do I need why am I breathing so hard I'm breathing so hard because I need more oxygen to keep this higher rate of cellular the respiration going you see what I'm saying so if I'm exercising at the gym too hard or if I'm trying to run a marathon I'm going to start panting oh my gosh panting because I need more oxygen to power this process and I need to breathe out more CO2 to get rid of that CO2 and I need to breathe in more oxygen breathe out more CO2 because I'm trying to make more ATP you see the problem here So eventually what's going to happen well I'm I'm breathing as hard as I can but I I may not be getting as much oxygen as I need right I may not getting as much oxygen in my blood as I need to keep this going right cuz this is happening in each and every one of my cells each of my cells is doing this cellular respiration so I need to breathe in oxygen and get it to all my cells in my body I just can't do that if I'm not training enough so what happens remember if there's not enough terminal electron acceptor do these electrons get picked up at the end of the ride that's right Wicket they don't and that means that that the electrons pile up like a freeway traffic jam and when the traffic jams all trafficked up right what happens this whole thing shuts down right oxidative phosphorilation shuts down what else shuts down remember I I mentioned it earlier what's what else shuts down that's right the citric acid cycle shuts down what else shuts down come on what else shuts down oxidation of pyate shuts down look at that and what's the only thing that keeps chugging along glycolysis right remember glycolysis occurs in the cytoplasm okay only only glycolysis is chugging along so when I'm when I'm uh doing too much activity when I'm doing too much exercise okay I'm doing too much exercise I'm not getting enough oxygen everything shuts down in my body in my tissues and my muscles everything shuts down except what except glycolysis okay so in this case instead of making a a nice nice profit I'm making instead of making 30 net ATP per glucose how many ATP am I making per glucose during fermentation by the way that's that's what fermentation is fermentation is when I don't have enough oxygen I don't have enough terminal electron acceptor and my and everything shuts down except glycolysis that's what the definition of fermentation right fermentation only glycolysis is going on because of lack of terminal electronic acceptor right so instead of 30 net ATP how many ATP am I making net during fermentation two right two net ATP so I'm making two ATP I'm making two nadh I'm making two pyate because that's all glycolysis is so that's what's happening during fermentation during fermentation I'm not getting enough terminal electron acceptor everything's shutting down except glycolysis so I've gone from making a whopping 30 ATP per glucose molecule to only two ATP net per glucose molecule that's not good can your body withstand that for a long period of time like if you were being paid $30 an hour can you now survive on only $2 an hour right you're going to you're going to come up short does that make sense and that's why if I tried to go for an a marathon right now and I haven't trained I'm going to start panting and panting and panting and breathing hard breathing hard breathing hard trying to get more oxygen but eventually this is what's going to happen I'm going to switch to fermentation and I'm only making two ATP where I was making only I was making 30 before now I'm only making two too and I can't withstand this things are going to start hurting and cramping up and spasming and I'm going to fall over I'm going to fall over I can't finish that Marathon you see what happens so this is fermentation you see how fermentation is not anerobic respiration in anerobic respiration the identity of my terminal electron acceptor is something else and humans aren't capable of anerobic respiration but humans are capable of fermentation because if we hit the gym too hard or go for a run too hard we will run out of oxygen in our muscles or run short and our and our muscles are going to switch to you know just doing glycolysis doing fermentation so in the next little clip I'm going to explain exactly how fermentation works by the way before I explain fermentation in a little more detail for you I'm going to explain why students confuse fermentation with anerobic respiration all the time and that's because It's Tricky the terminology is tricky sometimes fermentation is known as a anerobic process okay so F it's true that fermentation is anerobic it's true that fermentation is an anerobic process but let me ask you this is fermentation anerobic respiration right think about it respiration means that all of those steps were happening remember uh glycolysis oxidation of pyrovate citric acid cycle oxidative phosphorilation right all this stuff's happening all this stuff's happening that's not that's that's Anor robic respir anerobic respiration that's not what's happening during fermentation the reason why fermentation is called an Anor robic process is because anerobic just means without oxygen and yes fermentation is a process that happens when there's no Oxygen so yes technically fermentation is an anerobic process but it is incorrect to call fermentation anerobic respiration because the respiration part of that term means all those steps are working which obviously are not working so I hope that makes sense you it's okay to call fermentation an Anor robic process but it is not okay to call fermentation anerobic respiration just wrong right so now let me explain ferment in a little more detail and the type of fermentation I'm going to explain on the board right now is the exact type of for fermentation that happens in your body you know when you hit the gym too hard or you run that marathon when you're not trained right remember what happened when I started running really hard and I was not prepared for the marathon right remember breathing hard not getting enough oxygen to my muscles what happens remember everything shuts down except what except glycolysis right and do you remember how glycolysis works during glycolysis glucose is broken down into what remember three products of of glucose remember this glucose is broken down into two three carbon pyrates two molecules of pyrovate how many net ATP are formed during fermentation two and what else is formed during glycolysis right uh during glycolysis you have two P of two ATP and how many nadh two remember that's just glycolysis we learned glycolysis earlier right during glycolysis you make two pyrates 2 ATP two nadh fair enough okay but now did you know that you know during fermentation when I hit the gym too hard not only does stuff starts cramping up but if you've ever been in sports and if you've ever had a coach your coach coach might notice that you're spasming and cramping up and the coach might ask you to sit down okay and the reason the coach sits you down is because they explained to you that you might have what's called lactic acid buildup right during too much exercise my muscles can build up lactic acid some of you may have heard of this in the past well you know why because lactic acid is a fermentation product in animals right here's how it works okay let me explain why lactic acid is built up because is lactic acid is lactic acid a product of glycolysis no glycolysis results in two pyrovate 2 ATP and two nadh right so why are we producing lactic acid if all that's happening is glycolysis and lactic acid is not a product of glycolysis well let me explain let me explain okay here's how it works you ready okay here's how it works look normally I have plenty of sugar to keep this process going I have plenty of sugar okay and I keep I keep converting the sugar to pyrovate and I keep making 2 ATP that's great but here's what I need you to understand okay my nad+ the nad+ this oxidized carrier the oxidized form of the carrier nad+ is required it's required for glycolysis to continue right you know why because nad+ needs to come along and during glycolysis it picks up two electrons and a proton to become nadh right do you remember that nadh so I need nad+ because it gets reduced to nadh during glycolysis do you follow me so far but here's what I need you to understand your pool of nad+ is not very large your cells don't have an A overwhelming amount of nad+ at any time your mitochondria are not stuffed with nad+ this is a limited resource okay and here's the thing when you when that resource becomes reduced to NAD what what where does the nadh go at this point normally let me ask you this where does nadh normally go well where nadh always goes right it goes to the electron transport chain which complex which complex does nadh visit at the electron transport chain complex one or two yeah complex one complex one of the electron transport chain and then it drops off that H right it drops off those two electrons and the proton and what does it become what does it become doesn't it become oxidized back to nad+ and doesn't nad+ uh shuttle back to to pick up more H's you see how it normally works you guys follow me normally normally during respiration nad+ is reduced to nadh by glycolysis nadh goes to the ETC the electron transport chain complex one it drops off its H it drops off its two electrons and a proton gets oxidized back to nad+ nad+ can come back and do it again that's how we normally regenerate our pool of nad+ so that the cell does not run out of nad+ so the mitochondria doesn't run out of nad+ does that make sense you guys follow me so far that that's just a review right but let me ask you this during fermentation fermentation I've hit the gym too hard during fermentation is the ETC working is the electron transport chain functional during fermentation that's right Wicket it is not functional right so there is no Etc okay so is there a place for nadh to go drop off its h no right so think about this for a minute I just want you to think about this I told you that there isn't a ton of nad+ but you need nad+ to keep doing glycolysis but what's happening during fermentation is that your limited nad+ all of it's coming along and picking up electrons and becoming nadh so all of your nad+ all of your nad+ is becoming reduced to nadh and the nadh don't have any place to give the H right to replenish what to we need a way of replenishing we want to Replenish nad+ does that make sense if we run out of nad+ we are so you know out of luck because then glycolysis cannot continue does that make sense so we need a place to dump these H's because we can't take it to the electron transport chain so you know what we do we give the H to pyate look give that H give the h to pyrovate give the H to pyrovate and what does it become when you give pyate those H's those pyrovate become two lactic acids also known as lactates lactate an't that cool did you see what just happened did you see okay we needed a place to dump these H's so we don't run out of nad+ cuz we want more nad+ okay so we gave those H's directly to pyrovate and pyrovate got reduced pyrovate got reduced pyrovate got reduced to lactic acid and this is why during strenuous exercise during strenuous exercise your body will start building up lactic acid why because your body did not want to run out of the Limited resource nad+ and the only way to do that during fermentation is to reduce pyrovate to lactic acid thereby replenishing nad+ does that make sense so during lactic acid fermentation your body is only doing glycolysis you're only producing two net ATP and The Limited resource the limited factor that needs to be replenished is nad+ and how do you do it by reducing by using nadh to reduce pyrovate to lactic acid because when you give those hes to pyrovate pyrovate becomes lactic acid okay y'all ready for the final concept of this chapter alcohol fermentation did you know that not all creatures do the exact same fermentation so you and I as humans we undergo lactic acid fermentation which I just explained when you hit the gym too hard not enough oxygen you produce lactic acid as a fermentation product but different creatures on the planet Earth they can produce different uh products from fermentation so for example there's a myriad of different ones but I'll give you a common example called alcohol fermentation some creatures like yeast for example sacris Cici which is baker's yeast yeast when when it has oxygen it does aerobic respiration right so if I gave yeast oxygen plenty of oxygen and glucose the yeast would undergo respiration but what would happen if I shut the air off or or put the yeast in a closed bottle right then the yeast would switch to what if I were to block off the oxygen could the yeast continue to do aerobic respiration which includes glycolysis oxidation of pyate citric acid cycle and oxidative phosphorilation no because I've I've shut the I've closed the bottle right I've put the yeast in the bottle and I've closed the bottle now the yeast don't have any oxygen and so they run out of oxygen and what do they switch to the yeast will switch to fermentation right but they do a different kind of fermentation they do alcohol fermentation so I'm just going to explain that real quick and that'll be the end of the chapter so again during fermentation now this time it's alcohol fermentation again there's not enough oxygen the yeast do not have enough oxygen so they switch to just glycolysis they switch from aerobic respiration to fermentation so they're only doing glycolysis that means they're converting a glucose into two pyruvates they net two ATP and remember they're converting two NAD pluses to two nadh's right this is very similar to what we just discussed about lactic acid fermentation and remember I want to ask you this what's the limiting factor during fermentation that needs to be replenished can you beat wicket that's right Wicket it's nad+ remember nad+ needs to be replenished if you don't replenish NAD plus you're out of luck because all of it gets converted to nadh you run out of NAD plus plus and then you know you you're not even making two ATP for every glucose which means that's like pretty likely death right so so how do you combat that remember you and I you and I as animals we solve that problem by giving the H to pyrovate directly and pyate becomes lactic acid remember that but the only difference with alcohol fermentation is one extra step one extra step first the pyrovate is converted to acet alide to acid Al deide two acid alahh what what yeast do for whatever reason yeast yeast cleave their pyrovate releasing CO2 they release CO2 they first convert their pyate to acid alahh they first convert their pyrovate to acid alahh then they give it the H from nadh right so they give it that H that means that nadh gets oxidized back to NAD Plus and if you give acid aldah an H it becomes what it becomes two ethanol it becomes drinking alcohol it becomes alcohol and that's the same as drinking alcohol isn't that neat so it's the same basic principle as lactic acid fermentation but what's the only difference you still only make 2 ATP you're still only doing glycolysis you still only make 2 ATP you still need to replenish the nad+ the only difference is in you and me in lactic acid fermentation pyruvate is directly reduced to lactic acid whereas in alcohol fermentation pyrovate is first converted to acid aldhy and then that is that is reduced acid aldhy is reduced to ethanol right so isn't that neat and this is how alcohol is brewed did you know like how do you make wine how do you make wine don't you take grape juice you could add some sugar if you want you know so you got grape juice which has natural sugars or you could add a little more sugar so you've got sugar okay and then you got to add your yeast right you know your yeast cells which is sacris surer and then what do you need to do with that container can you just leave that container open if you want to make wine or do you have to close the barrel like like plug the barrel up remember yes you have to plug the Barrel up why do you need to plug that Barrel up if you want to make wine well because you want the the yeast to switch from aerobic respiration where they're not going to be making any ethanol to fermentation where they are going to be making ethanol why because during fermentation those yeast cells are just doing glycolysis so the yeast are taking the glucose from the grape juice or from you know the the sugar that you put in the grape juice the they're converting that glucose and the grape juice to pyrovate they're getting 2 ATP they're converting nad+ to nadh they need a way of of getting their NAD plus back so what do they do instead of giving that H directly to pyrovate like we do they first convert the pyrovate to acid aldhy and then they reduce the acid aldhy to ethanol thereby making wine thereby making the alcohol in wine isn't that neat and yes those barrels can get bubbly right because there's CO2 produced as well isn't that neat so CO2 is produced during this process so now tell me you're not impressed tell me it's not interesting right cuz students you know a lot of times cellular respiration can be dull Bland boring what have you yeah it can be but at the same time look what you've just learned you've learned why you breathe oxygen you've learned why you breathe out CO2 you've learned how you gain weight or lose weight you lose most of your weight through exhaling CO2 you've learned why you diet because you don't want to replace those sugars and those fats immediately after you've converted them to CO2 you've learned why when you hit the gym too hard you get cramps and everything gets all lactic acidy right because you would need to replenish your nad+ by reducing pyate to lactic acid and you've learned the principles behind behind alcohol fermentation you know yeast cells they're doing fermentation of their own they need to replenish nad+ so they first convert their pyrovate to acid alahh and then reduce that to ethanol now I think that's a pretty interesting chapter Dr D Dr D Dr D Dr D Dr D Dr D Dr D Dr D Dr D Dr D Dr D D Dr D A Dr D Dr D Dr D Dr D Dr D Dr D A Dr D Dr D Dr D Dr D Dr D Dr D