hi it's kim and today i am talking to you about cell respiration also called cellular respiration i am going to write cellular respiration once and after that i am going to only write and say cell respiration because it's easier okay cellular respiration is one of the two major energy processes that we are talking about the other one is photosynthesis i want to start by making it really clear that it's not an either or thing a lot of students get confused and think that living organisms either carry out photosynthesis or cellular respiration but cellular respiration is carried out by all living organisms and what do i mean by that i mean all living organisms so that includes bacteria and archaea which of course are the prokaryotes and then it includes all the eukaryotes so protists fungi plants and animals this is how living organisms take the energy from their food and convert it to the form that cells need to carry out chemical reactions and that is atp so in the shortest possible version of answering the question what is cellular respiration it is the process used by all living organisms to make atp from the energy in food molecules with glucose being the preferred food molecule for that all living organisms must do this chemical reactions in living cells cannot directly use the energy available in food molecules it has to get converted to another form so be just as if you visited a country that didn't accept u.s currency and you had to exchange that money for a different form of money it's the exact same process in a way because you're just taking one form of energy and you're exchanging it for another form of energy energy is lost in the process it's not 100 transfer so just like you pay an exchange fee sometimes to exchange that money we're going to pay an exchange fee to make that atp also important to realize what it means when we say make atp and we talked about that in the energy lecture but i'm going to remind you of that again in a minute who on this list carries out photosynthesis not all living organisms right so photosynthesis obviously plants carry out photosynthesis some protists carry up photosynthesis in fact when we talk about photosynthesis in detail in a separate lecture you're going to see that photosynthetic protists are the base of the food chain in aquatic systems incredibly important there are not multicellular plants in the ocean and then some bacteria can carry out photosynthesis so not all organisms carry out photosynthesis but all living organisms carry out cell respiration let's look at the connection between those chemical processes so the incoming ingredients for photosynthesis are water and carbon dioxide and then the other important ingredient is light energy from the sun and through the most important chemical reaction on earth all life on earth depends on this chemical reaction called photosynthesis these organisms are able to take light energy from the sun and convert it to chemical energy that the entire food chain can use including themselves we typically use glucose as the carbohydrate that is produced when we talk about this but plants and protists and bacteria can produce other sugars through photosynthesis as well and you'll see that when we talk about it in detail and also oxygen is produced during photosynthesis these are then the ingredients that are needed for cellular respiration in cell respiration living organisms take the energy in that food and convert it to atp and in the process produce water and carbon dioxide if you recall the general equation for cell respiration and the general equation for photosynthesis that we've already talked about several times those are the reverse of each other so remember that general equation for cellular respiration glucose and oxygen becoming co2 and water the opposite of that was photosynthesis so remember photosynthesis was carbon dioxide and water becoming glucose and oxygen so that's the connection between those two processes again not all our canvases but all living organisms carry out cellular respiration why do these photosynthetic organisms do this they're not just being nice they're not being charitable and doing this for the rest of the food gene they're doing this because they don't eat they can't eat so they have to produce their own energy they then provide the energy for the rest of the food chain because we aren't able to take light energy from the sun and convert it to food we either have to eat a photosynthetic organism or eat somebody who eat a photosynthetic organism so this is a very very important connection to realize okay i also want to remind you what it means when we say make atp during cellular respiration making atp in cellular respiration means phosphorylating adp to atp what do we mean by that remember phosphorylation means transfer of a phosphate group from one molecule to another in this case that phosphate group is getting added to adp to make atp i'm going to show you that in just a little bit more detail so just a reminder of the structure remember adp and atp are both nucleic acids so the basic structure it starts off looking a lot like an rna nucleotide it's the ribose sugar the base is adenine and i'm just going to draw a very simplified version with an a with a circle around it and then if this was an rna nucleotide it would just have one phosphate group but i'm going to draw atp first adenosine triphosphate so atp means adenosine tri phosphate three phosphate groups so one's already drawn there's number two and then number three we draw with a squiggly line which indicates that that is a high energy bond and when it's broken a lot of energy is released i'm not going to go into the reasons for that being a high energy bond if you take a higher level biology class you might go into the reasons for that but it's important to realize that breaking that bond and transferring that phosphate group that equals energy okay because it's exergonic remember exergonic reactions release energy and now that phosphate group is going to go to another molecule and give that molecule energy to go do what it needs to do so either combined with something else or break apart whatever is needed that transfer that phosphate group breaking that high energy bond and releasing that energy is going to provide the energy to carry out another reaction but what we're left with as a result is a molecule that now just has two phosphate groups because that third one was transferred so we now just have adenosine diphosphate adp so again transfer of that phosphate group breaking that bond and transferring that phosphate group to another molecule energy was released when that bond was broken and that energy that was released is now being transferred in the form of that phosphate group so when that phosphate group gets transferred that provides energy to something else to carry out a chemical reaction that is an energy transfer remember that exergonic reactions are coupled with endurgonic reactions endergonic reactions require energy input another important endergonic reaction is adding that phosphate group back onto adp to regenerate atp that is going to be endergonic so adp becoming atp again is going to require a phosphate group to get added back on and that is endergonic okay which means energy is required and that's what's going to happen during cellular respiration so again in cell respiration when we say we're making atp we're not making atp from scratch we're rephosphorylating adp to make atp where does that energy come from during cell respiration it's going to come from two potential energy sources so energy for phosphorylating adp during and i'm going to now start calling it cell respiration it's simpler for all of us it's going to come from two sources one is going to be the potential energy that's stored in the covalent bonds of our food molecules in particular glucose that's going to be one important source of energy that is going to be used to phosphor forelate adp back into atp and the second is going to be the potential energy in a very important concentration gradient that is going to be established during cellular respiration remember that concentration gradients and covalent bonds are both excellent sources of potential energy in the cell and both of those are going to be sources of energy for adding that phosphate group onto adp to produce atp there are going to be two methods or phosphorylating adp to form atp and it's important to know these two terms one is called substrate phosphorylation and the other is called oxidative phosphorylation when i summarize the four major steps of cell respiration i am going to point out which method of producing atp is being used during that stage that's producing atp so i'll be using these terms again i'm not going to explain them further at this point but i will when we get to those stages where those two methods are using being used so just for now realize two energy sources for phosphorylation and then two methods of carrying out phosphorylation so that's the difference between those two pieces of information so the energy for carrying it out is going to come from covalent bonds and a concentration gradient the methods are going to be either substrate-level phosphorylation or oxidative phosphorylation i know those sound like big terms but when we break them down they're not going to seem as complex okay how also involved in this story are some really important electron carriers and i will be talking about them as we go along as well so those are going to be some key players in the story now for the quick overview of cellular respiration i'm going to tell you the four major stages i also want you to realize that i am giving you a very simplified version i don't want you to know all the details of each step of each of these four major stages some books will tell you there are three stages because they don't count pyruvate oxidation as a stage i am counting it as a stage as do many other textbooks i will also show you some pictures at the end that will summarize all of this a little better than my drawings but for now i want you to draw so i'm going to draw so that you'll draw okay four major stages of cell respiration again cellular respiration is just too much for us to say every time for now i'm just going to list them with no further explanation glycolysis pyruvate oxidation citric acid cycle also called the krebs cycle and finally oxidative phosphorylation oxidative phosphorylation is going to have two major parts one is the electron transport chain and then the other is chemiosmosis this is a very complex metabolic pathway remember during the energy lecture i talked about metabolic pathways in the fact that they are multi-step the product of one stage becomes the reactant of the next stage and we finally will end up with an end product there are also enzymes involved at each stage i am not going to ask you to know the intermediates i'm also not going to ask you to know the enzymes but i just want you to realize this is a very complex process and i am just giving you the very basic version you don't for this 100 level class need to know more than this you can always plug details in later so if you go on to take a higher level bio class whether it be microbiology physiology bio 200 for bio majors you will hit cell respiration again in more detail i believe if you can understand the basic version you can plug details in later so i know that it's complex i know that these terms are a little overwhelming i am going to give you a chart at the end that i think does a really good job of summarizing everything so if you don't get it the first time around please just watch this video a second time a third time and again i don't need you to know all of the details i need you just to know what i'm telling you also important to realize there is a cell respiration worksheet and if you can answer all the questions on the worksheet then you'll be able to answer all of the questions on the exam so that's important to realize too okay where is this all happening okay this is happening in our cells so important to realize that i'm going to draw just a giant cell here and i'm going to draw the nucleus pretty small dna so remember that for glucose to get into our cells it requires insulin but i'm you know not even going to get into that level of detail let's assume that this glucose got into our cells and now here it is in the cytoplasm of the cell so for the purposes of this lecture we can really assume that this region between the nuclear envelope and the plasma membrane this whole region is called the cytoplasm the liquid portion of that is sometimes called the cytosol so that would be the liquid portion so if you read a textbook i'm pointing this out because if you read a textbook about cell respiration some textbooks will say that this first stage takes place in the cytoplasm some will say cytosol i just want you to realize those are really saying the same thing it's in the same region of the cell so glucose enters the cell and then it's going to immediately go into the first stage of cell respiration which is called glycolysis glycolysis that means sugar splitting if there's enough oxygen present then the breakdown of the products of glycolysis will continue if not it's going to go through something called fermentation and we're going to talk briefly about fermentation also but first we're going to talk about what's referred to as aerobic respiration so aerobic means with oxygen the other possible type of respiration is called anaerobic respiration and i'm sure you've heard these terms before related to exercise this means without enough oxygen so and means without we're going to start by talking about aerobic respiration then we will talk briefly about anaerobic respiration the other term for this is fermentation fermentation produces some amazing products that we use and we'll talk about that as well but for this first round i'm going to be talking about aerobic respiration what happens when there's enough oxygen present but it's important to realize that this first stage glycolysis can happen with or without oxygen so glycolysis the first stage of cellular respiration so i'm just going to put a number one here to indicate this is the first stage and it means sugar splitting so glycoglycogen remember is a chain of glucose glyco is a term that just refers to as sugar to lice is to break or split this you can call this sugar breaking sugar splitting and this is happening in the cytoplasm of the cell when glucose first enters the cell and that's what we start with in glycolysis the cell starts with glucose and glycolysis is pretty complex it's 10 steps i don't want you to know those 10 steps but i want you to realize that the product of the first step then becomes the reactant of the second step okay and then the product of that step becomes the reactant of the next step there are enzymes involved at each stage and throughout those 10 steps we need to use 2 atp as an energy source to get things started so there is an energy investment phase in which two atp are used but we make 4 atp throughout glycolysis and at the end of these 10 steps we have a product in which we started with a six carbon glucose and we now after ten steps have split it into two three carbon molecules called pyruvate and those are each three carbon molecules we also do something really important during glycolysis and that is that the electron carriers are going to start picking up hydrogens from that original glucose molecule so just to quickly remind you of the general equation for cellular respiration thank you 36 atp that's a very general number okay some books will say 36 to 38 realize that this is just on average and but it is the number that i'm going to use today is the number that most textbooks use just for accounting purposes okay but realize that's just an average every cell does it a little differently every person does it a little differently it might not be the exact same every time but on average we make 36 atp for every one glucose important to realize oxygen is required for the aerobic respiration that we're going to be talking about carbon dioxide and water are products we're going to keeping track of co2 as we go along we're also going to be keeping track of what happens to glucose as it's being broken apart and of particular interest are these 12 hydrogens those hydrogens are going to get picked up by electron carriers and eventually stripped away from those electron carriers to set up the concentration gradient that's going to be used to produce most of the atp during cell respiration so it's important to follow those 12 hydrogens throughout the process in glycolysis two of those hydrogens are picked up by the electron carrier nad plus to make two nadh so during glycolysis the first two of those hydrogens are picked up and this electron carrier is that now going to shuttle those hydrogens and their accompanying electrons to a very important stage at the very end but again it's important for us to track those 12 hydrogens because those are going to be a major energy source at the very end when that concentration gradient is set up so summary of glycolysis what do we start with we start with glucose what do we end with we end with two pyruvate molecules how many atp were made four were made but two were used so that's a net of two atp that were generated during glyphosis where is this taking place it's taking place in the cytoplasm of the cell and this is by the way the only stage that can take place with or without oxygen i know we're just talking about what happens with oxygen right now but glycolysis can happen with or without oxygen it's the only stage that can happen without oxygen all of the other stages are going to require oxygen to take place also important to realize we picked up the first two of the 12 hydrogen and made two nadh nad plus is an electron carrier and when it picks up electrons it becomes nadh remember gain of hydrogen equals gain of electrons and leo the line says ger so gain of electrons is reduction so this is reduction okay we would say that nad plus is reduced and the reaction is called reduction to become nadh in a few minutes when we talk about those hydrogens being stripped away remember loss of electrons is oxidation so nadh is going to get oxidized when those electrons and the hydrogens get stripped away so that's the summary of glycolysis i'm going to summarize this in a table at the end just as in these 10 steps the product of one stage becomes the reactant of the next stage that happens here also so now we ended with these two pyruvate these two pyruvate are now what we're going to use to start the next stage called pyruvate oxidation okay so second stage of cellular respiration is called pyruvate oxidation okay start with two molecules of pyruvate that were the products of glycolysis these are each three carbon molecules three carbon molecules cannot enter um citric acid cycle a carbon needs to get shaved off from each of those this used to be called the grooming stage it used to be called the transition stage it's had a number of different names it even saws a number of different names for this class we're calling it pyruvate oxidation so we start with two pyruvate and what's going to happen is for each of those pyruvate molecules a carbon is going to be lost as co2 so two co2 are going to get released one per pyruvate okay also two hydrogens are going to get picked up by nad plus to form 2 nadh and what we're left with at the end is two molecules of what's called acetyl coenzyme a it's written co a for short those are two carbon molecules a coenzyme gets attached in the process too you don't need to know that level of detail two carbon dioxides are released that is important to know that's two of our carbons from our c6h12o6 we picked up two more hydrogens so now we've picked up four total of those 12 hydrogens remember c6h12o6 12 hydrogens we picked up two in glycolysis we've now picked up two more in the transition phase no atp is made in pyruvate oxidation why is this stage necessary this stage is necessary because we can't break we can't complete the breakdown of glucose without the citric acid cycle citric acid cycle requires a two carbon molecule called acetyl coenzyme a so this transition phase also called pyruvate oxidation is necessary okay important to realize that even though atp is not made it's an important transitional phase and that's why it used to be called the transition phase it's a transitional phase between glycolysis and citric acid cycles so that's why some textbooks don't call it a separate stage of cell respiration but for this class we do call it a separate stage also important to realize where this is happening and it only happens if oxygen is present so pyruvate oxidation requires oxygen and where is it taking place it takes place in the matrix of the mitochondria so i'm going to draw a mitochondrion to remind you of where the matrix is and the structure of this mitochondrion is going to be really important as we go through these next stages of cellular respiration so i'm going to go back to the cell for a minute here's the cell again nucleus out here in the cytoplasm glucose came into the cell it went through glycolysis glycolysis sugar splitting and it produced two pyruvate out here in the cytoplasm now if oxygen is present so i'm just going to say if o2 those two pyruvate are going to go into the mitochondrion and complete the breakdown of glucose okay if no o2 then fermentation is going to happen anaerobic respiration but we're going to talk about that separately now we're just going to talk about if o2 is present if o2 is present then those two pyruvate go into the mitochondrion and that's where pyruvate oxidation citric acid cycle and oxidative phosphorylation are all going to take places in the mitochondrion so looking at that mitochondrion blown up bigger and recalling the structure of this the inside region here is called the matrix this is the outer membrane this is the inner membrane this space between the two membranes this space here is called the inter membrane space it's a space between the two membranes this is important because different stages of cell respiration are going to take place in different regions of that mitochondrion okay so remember one mitochondrion that's the single mitochondria is the plural so we're just talking about one of them right now pyruvate oxidation and citric acid cycle are both going to happen in the matrix oxidative phosphorylation is going to happen in several different regions and we'll talk about that also important to realize when we say membrane membrane always means mostly a phospholipid bilayer with some important proteins embedded so membrane is a phospholipid bilayer so if we blew up that outer membrane if we blew up that inner membrane you would see mostly phospholipids forming a bilayer like with those heads pointing outward and the tail is pointing inward and then they're going to be some really important proteins embedded in that membrane as well and then more phospholipids that's going to be an important part of the story as well it's just the structure of that membrane so that's true the outer membrane and the inner membrane the inner membrane of the mitochondrion in particular is going to be an important part of this story in helping set up a very important concentration gradient to generate most of our atp okay so glycolysis happened out in the cytoplasm to produce those two pyruvate and then if there's enough oxygen present those two pyruvate go into the matrix of the mitochondrion and that is where pyruvate oxidation and citric acid cycle are going to take place is in the matrix of the mitochondrion so now we've produced two acetyl coenzyme a in the matrix and now the third stage of cellular respiration is going to happen and that's called the citric acid cycle okay and in the citric acid cycle we start with what we ended with last time so in the previous step we ended with a two acetyl coenzyme a called acetyl coa and i'm going to go through multiple steps you don't even need to know the number i know i told you 10 on glycolysis i kind of regret doing that now because i don't want you to fixate on how many steps it is we're going to go through multiple steps and during this citric acid cycle the breakdown of glucose becomes complete as four co2 are going to get released and eight hydrogens are going to get picked up with electron carriers mostly by nad plus but there's going to be another electron carrier that's used also six nadh are going to get produced and two fadh2 are going to get produced when an electron carrier called fadh picks up two electrons remember there are two acetyl-coa coming through citric acid cycle so really it's three nadh and one fadh2 for each of those two so i'm just combining the sum total of what happens in citric acid cycle two atp are going to get produced and as i said a minute ago four co2 are released and at the end of the citric acid cycle nothing is left of glucose just all of the 12 hydrogens being carried by the electron carriers and just to remind you we made 2 nadh in glycolysis two nadh in pyruvate oxidation six nadh and 2 fadh2 in the citric acid cycle 6 8 10 12 that's 12 hydrogens remember c6h12o6 so that's our 12 hydrogens this carbon and oxygen were released as co2 along with part of the oxygen so remember the reactants include not only glucose but six oxygen so remember the way this works six o2s that's 12 oxygens okay that's six oxygens so that's 18 oxygens total if we release six co2 remember two during pyruvate oxidation and four in citric acid cycle that's the six that's six carbons and 12 oxygens so minus 12 oxygens there's six oxygens left so at the end of the citric acid cycle all the hydrogens have been picked up by electron carriers carbon and oxygen have been released as co2 so there's our six carbons six carbons released to co2 12 of the oxygens have been released to co2 all the hydrogens are being carried by electron carriers so there's nothing left of glucose at the end of the citric acid cycle but we've only made four atp we need to make 36 total but glucose is gone so all of that potential energy in the covalent bonds of glucose remember that was one of our energy sources that's all been used up that only allowed us to make 4 atp so 2 atp in glycolysis and two atp in citric acid cycle i'm just abbreviating it for now that means 32 more need to get made but glucose is gone okay so how were these made these were made by a process called substrate level phosphorylation so all four of these are all made okay so all four were made remember we actually made four in glycolysis but we used two so we actually made six total but we've used two so all four of those net were made by the process called substrate level phosphorylation what does that mean let's break this down substrate level think back to enzymes remember that an enzyme has a very specific shape and i'm just going to draw a pretend shape here remember that this part where the reactant binds is called the active site of the enzyme and when a reactant binds to an enzyme it's called the substrate so the substrate is the reactant in an enzyme catalyzed reaction and in this case this substrate has a phosphate group attached to it and it's going to transfer that phosphate group to adp so this is adp and this enzyme is going to facilitate transfer of that phosphate group remember transfer of a phosphate group is called phosphorylation and in this case transfer of a phosphate group from a molecule to adp to make atp and that is called substrate level because it's taking that substrate the reactant and transferring that phosphate group phosphorylation transfer the phosphate group to adp to make atp if you really want to look at the steps of glycolysis in the citric acid cycle you can see which specific enzyme is involved in doing that and which exact reactant or substrate is used to basically donate that phosphate group and transfer it to adp to make atp that's how we made those first four atp 2 in glycolysis and 2 in citric acid cycle i want to just quickly draw a chart to summarize everything that's happened so far before we get to oxidative phosphorylation at the end which is how we're going to make 32 more atp but i think that this chart will help really summarize it i just i want to make sure i don't leave off anything so um i'm going to try to write small here and i actually want my grid lines okay so this is going to be our stage start with end with i'm going to skip the wear because it can't really fit on this but i'm going to mention the wear i just i'm not going to put it on the chart because it doesn't really fit in that place method of atp production electron carriers i'm just going to call them e carriers and co2 okay i only have four stages but i have a feeling i'm going to have to write um like below the line sorry i know this is really messy but i promise this will help it will help summarize everything okay first stage glycolysis we start with glucose glucose enters the cytoplasm of the cell so i'm going to say glycolysis in the cytoplasm again we could say cytosol go through a lot of steps don't need to know the numbers and just forget that i ever even told you that it was 10 okay end with two molecules of pyruvate number of atp produced two net remember we used two and made four but it's two net made by substrate level phosphorylation which i'm just going to prove abbreviate slp electron carriers 2 nadh were made the first two of those 12 hydrogens were picked up sorry i'm going to write that a little neater 2 nadh and no co2 were released in glycolysis and remember this is the only stage that can happen with or without oxygen if enough oxygen is present then we go into the second stage which is called pyruvate oxidation and that happens in the mido matrix which is of course mitochondria and i don't know how that just happened but yeah my hand when it touches the screen does all kinds of crazy stuff okay again we start with what we ended with in the last stage so we ended with two pyruvate that means here we start with two pyruvate sorry it's so small there and that's a two end with two acetyl coenzyme a i'm just gonna make that two a little better there number of atp made zero so this is not applicable number of electron carriers two nadh and two co2 were released that's how we made those two acetyl coa by shaving off a carbon from each of those two pyruvates remember the pyruvates were three carbon molecules the acetyl-coa are two carbon molecules and now we go into the citric acid cycle which also happens in the mitochondrial matrix so oxygen is required so citric acid cycle in the mido matrix start with two acetyl-coa end with nada okay we completed the breakdown of glucose so there's nothing left of glucose okay just those electron carriers just the 12 hydrogens that's all that's left so that's where all the potential energy now is we've only made 4 atp because remember we make two more atp by substrate level phosphorylation six nadh and two fadh2 and four co2 are released so there's all six of our co2 here's our twelve electron carriers six eight ten twelve so now all of the potential energy is in those electron carriers because glucose has broken down it's been released as co2 the hydrogens are being carried by the electron carriers at the end of the citric acid cycle that's where all the potential energy is now is in those electron carriers that's a really important point and there is a question on the worksheet about that to point out how important that is okay so at the end of the citric acid cycle all the potential energy is now in those 12 electron carriers again i apologize for how messy this chart is but i do think it's really important to kind of summarize everything in your brain and this is a good way to really summarize it now we need to make 32 more atp and that's going to happen in the last stage called oxidative phosphorylation and oxidative phosphorylation doesn't really fit into this chart okay this is just going to be a stage in which a lot of atp are generated because of this concentration gradient that's going to get set up so oxidative phosphorylation if we had to fit it in the chart we would say we start with the 12 electron carriers where is this happening i'm going to say the entire mitochondrion is really being used everything except the outer membrane is being used number of atp made is going to be on average 32 atp and they're made by a very important enzyme that is embedded in the inner membrane of the mitochondrion so let's look at the structure of that mitochondrion again oops sorry in living systems whenever something is folded it increases the surface area imagine that you cut this outer membrane and you took this as a just imagine it being a strain okay we know it's phospholipids with some proteins embedded in but imagine you stretch it out that's going to be a lot shorter in length than this if we did the same here this is a lot longer it's folded right folds increase surface area so anything that's happening you've got to know there's something really important happening in that membrane embedded in this membrane are some really important protein complexes that make up something called the electron transport gene okay so these are proteins that are embedded in that inner membrane so remember this is the matrix this is the inner membrane this is the outer membrane and this is the inter membrane space in between here so we have all 12 of those electron carriers here we have the 10 nadh and the two fadh2s that were generated in those first three stages when those electron carriers were reduced they were reduced when they picked up the hydrogens gain of electrons is reduction ger they're now going to lose those electrons they're going to become oxidized that's why this is called oxidative phosphorylation those 12 electron carriers are going to be oxidized because what happens is when they come in contact with these proteins in the inner membrane of the mitochondrion those hydrogens are going to get stripped away and pumped out into this space this inter membrane space they are charged this is a really important thing to realize the electrons are being stripped away and they're getting bounced through these proteins in something called the electron transport chain and those electrons are generating energy as they fall down this energy ladder they're generating energy to pump those hydrogens against a concentration gradient out into this space so there are a lot of important concepts involved here one is you know that the energy generated by those electrons falling down an energy ladder is giving energy to pump those hydrogens against a concentration gradient and they're building up out here they can't just come across the phospholipid bilayer because remember that charged ions cannot move across those nonpolar tails remember charged ions or molecules cannot simply diffuse by simple diffusion across phospholipids what happens is those 12 hydrogens are going to build up in this inter membrane space and that now represents a concentration gradient okay so hydrogens are stripped from the electron carriers by proteins in the inner membrane of the mitochondrion and they are pumped into the inter membrane space where they build up and they create a concentration gradient so a concentration gradient is established all of those hydrogens are now representing a ton of potential energy when they come back across the membrane they're not going to come across across the phospholipids they can only come across one way they can only come back across the membrane remember that to reach equilibrium they need to come back so they're high out here and they're low over here but they can't just cross that phospholipid bilayer so now through facilitated diffusion they're going to come across a very important protein so they can only come back across the membrane by what's called facilitated diffusion through a very important protein one of the most important proteins in your body and it's called atp [Music] synthase remember enzymes are cool because the name tells you what they do and they end in asc so this asu tells us that it's an enzyme it's going to synthesize atp when those hydrogens come back across through that enzyme it's going to phosphorylate adp to form atp and i'm going to show you a picture of that happening but first i want to go back to my picture here here's atp synthase here's atp synthase they're going to be scattered throughout this membrane and that's the only way that hydrogens can come back across okay so here's the atp synthase and the hydrogens can only come back across through that enzyme they can't come across that phospholipid bilayer because they are charged and when they come back across it's going to phosphorylate adp to form atp so if this is adp [Music] and it's just sitting there waiting as those hydrogens come across it generates energy to phosphorylate to stick phosphates back on that adp to form atp and i'm going to show you a picture of that happening in a minute but for now i'm going to blow up that membrane i'm going to draw a blow up of that inner membrane so if we look at the mitochondrion again sloppy version i'm going to just take a piece of that and blow it up so i'm blowing up that inner membrane and it's phospholipids which hydrogens cannot come across it's some important protein complexes and you don't need to know about these in detail okay here's another one and what happens is when those electron carriers come in contact with those protein complexes those protein complexes are going to strip the hydrogens away and pump them out into the space oops sorry i didn't mean to do that and then this is going to be our atp synthase and it's kind of like a rotor more phospholipids okay and on this side we have a bunch of adp and we have a bunch of phosphate groups okay nadh comes in contact with this protein the hydrogen is going to get stripped away and pumped out into the space and what we're left with is nad plus loss of electrons is oxidation so that nadh became oxidized to form nad plus and that hydrogen gets pumped out into this space okay that's going to keep happening and these hydrogens build up out here they can't just come across that phospholipid bilayer because they're charged but they can come across through the atp synthase and when they do this rotor spins and it sticks phosphate groups onto adp to form atp and 32 atp on average are going to get generated through this process important terms here the protein complexes stripping away those hydrogens and pumping them out into that space is called the electron transport chain and when the hydrogens come back across and generate the atp by phosphorylating adp with the energy of them coming back across it's like water behind a dam coming through a hydroelectric plant and generating electricity that potential energy is coming from that concentration gradient that part is called chemiosmosis those hydrogens coming back across those two together make up what's called oxidative phosphorylation sorry it wouldn't all fit on that one line oxidative phosphorylation i'm sorry there's some really loud construction noise going on outside of my neighbor's house right now those are the two stages of oxidative phosphorylation electron transport chain the hydrogens are stripped away those electron carriers become oxidized that hydrogen is pumped out into the space chemiosmosis is when those hydrogens come back across and phosphorylate adp to form atp i'm going to show you a better picture of that in a minute that's how 32 atp are generated at the end okay so if we tried to fit that into the chart up above here's our chart again we just start with the 12 electron carriers and we make 32 atp really by chemi osmosis i mean the cumin has the most as part is where they get made i mean they say that they're made by oxidative phosphorylation but they're made during the kidney osmosis part of that i would never ask you a question to make that distinction i would just ask you how many atp are generated during oxidative phosphorylation realize that it's all because of that magical enzyme called atp synthase which i'm also going to show you a picture of so i'm going to show you a better picture of the electron transport chain a better picture of atp synthase just want to double check that there wasn't some other picture i wanted to draw for you okay we also need to talk about fermentation and i'm going to do that on the diagrams too okay i would love to ask you right now if you have any questions but we are not live so i can't do that but i know this is a lot because it's a lot on the surface it seems really really boring but just realize this is an amazing process like how cool is this that we can take energy from our food and we can package it as atp and we can use it anytime anyplace in the cell we don't have to have a gas tank that's full we don't have to be on a glucose drip all day long we can take that energy from our food and we can convert it to an energy currency that can be used anytime any place in the cell and remember i've told you before you make and use your body weight in atp every day that's pretty amazing too if you stop making atp you die rat poison called cyanide is blocking a stage of cell respiration there are a lot of poisons that block key stages of cell respiration and cause death of that organism whether it be a plant an insect different pesticides are used to do that so and there are different poisons that are used to do that too you must make atp all day every day otherwise the chemistry of your cells shuts down because remember you can't directly use energy from your food you have to convert it to atp and that atp is then used to drive chemical reactions that require energy in the cell okay i'm going to pull up some pictures so please just stick with me for a second here while i pull up these images this didn't work okay these are the photos i want to show you of cellular respiration these are some better images than what we drew together in the notes so this is nad plus it's one of the two electron carriers remember the other one is fadh and that becomes fadh2 and you can see that it is a nucleotide and when it picks up hydrogens it's becoming reduced when it drops off a hydrogen it's becoming oxidized so i just wanted to show you that better picture this is just an overview of cell respiration it's showing that glycolysis takes place out on the cytosol again you know this term cytosol and cytoplasm can be used interchangeably but during this process we make two atp net by substrate level phosphorylation it doesn't show pyruvate oxidation happening but pyruvate oxidation is going to happen here in the matrix of the mitochondrion and again this is only if oxygen is present that those two pyruvate go into the mitochondrion pyruvate oxidation produces the acetyl coa that then go through citric acid cycle and remember at that point we've completely broken down glucose all the energy is now in those 12 electron carriers and we make two more atp net by substrate level phosphorylation and then finally at the end during oxidative phosphorylation which includes the electron transport chain and chemiosmosis on average 32 atp are made by oxidative phosphorylation and remember it specifically during the chemiosmosis when those hydrogens come back across that those um 12 i'm sorry 32 atp are being made this shows you a picture of substrate level phosphorylation and i already drew this picture for you but it shows that substrate is the reactant that's going to transfer a phosphate group to adp to make atp and remember that we make two atp in glycolysis by substrate level phosphorylation and we make two in citric acid cycle by substrate level phosphorylation this slide got a little wonky but this is the first five stages of glycolysis remember it's 10 stages long but you don't need to know that you start with glucose we're going to use some atp here we're going to use some atp here to get things started and then at the end of the 10 we've made four so remember we used to make four so that's two net atp you can see there is an enzyme involved at each stage so anything that ends in ase is an enzyme and you can see that the product in one stage becomes the reactant of the next stage just like in any other metabolic pathway so this three phosphoglycerate is a product of the prior stage and then becomes the reactant of the next stage and at the end we end up with two molecules of pyruvate that are three carbon molecules one two three and we end up with two of those those two then go through pyruvate oxidation so let me go back down here so if oxygen is present the two pyruvate go into the mitochondrion and go through pyruvate oxidation where those two acetyl-coa are produced but then goes through a citric acid cycle if there's not enough oxygen present we go through fermentation this is pyruvate oxidation so for each pyruvate one carbon dioxide is released and since we have two pyruvate sorry this is really writing fat right now two pyruvate are you gonna make two carbon dioxide two nadh and we end up with two acetyl coa that e should not be on the end those two acetyl coa then go through citric acid cycle you can see those steps of citric acid cycle here again you don't need to know these eight steps but you can see we start with the acetyl coenzyme a and you can see where we pick up the hydrogens with the electron carrier so remember we have two of these so everything gets doubled so if you count all the nadhs one two three but that gets doubled so that's six nadh and then this gets doubled so two fadh2 and this gets doubled so it's 2 atp these are the protein complexes that are embedded in the inner membrane of the mitochondrion and this is atp synthase i'm going to come back to that picture in a minute because i want to show you this first so this shows us protein complexes stripping away those hydrogen so nadh is becoming oxidized loss of electrons is oxidation the hydrogens get pumped out into the space using the energy generated when those electrons fall down this energy staircase and all those hydrogens build up out there they can't come across these phospholipids because remember they can't cross those nonpolar tails so they're not allowed across there the only way they can come across is through atp synthase and when that happens adp is phosphorylated to form atp and that part is called the chemiosmosis so i really like this explanation it says electron transport chain electron transport and pumping of protons which are the h plus which creates an h plus gradient this is a concentration gradient across the membrane and then chemiosmosis is atp synthesis powered by the flow of the h plus back across the membrane when those come through that produces enough energy to add that phosphate group onto adp to make atp and on average we make 32 that way oh boy sorry when it gets towards the edge it just really gets wonky over there sorry so 32 on average atp get made that way also one thing we haven't talked about yet the final electron acceptor oxygen when those hydrogens come back across they're going to finally join up with oxygen and produce water so remember that general equation sorry let me write it up here c6h12o6 plus 602 six co2 remember two were released in pyruvate oxidation and four were released in the citric acid cycle those oxygen now are going to combine with those hydrogens to form the six waters okay this is a good summary slide i like the summary slide the only thing it doesn't show you is it doesn't show you pyruvate oxidation in detail but it shows you that glycolysis takes place out in the cytoplasm you start with glucose you end with two pyruvate and produce two atp by substrate level phosphorylation if there's enough oxygen present you go into the mitochondrial matrix and make two acetyl coa through pyruvate oxidation which then go through the citric acid cycle and we make two more atp by substrate level phosphorylation and then all of those electron carriers go into oxidative phosphorylation because when they hit that inner membrane in the mitochondria the protein complex is embedded in that inner membrane strip away those hydrogens they get pumped into the inter-membrane space they can only come back across through atp synthase and here's that amazing amazing enzyme that is going to phosphorylate adp to form atp when those hydrogens come back across the most amazing membrane a membrane the most amazing enzyme so this is the number one enzyme in my book this is an incredible enzyme can you even imagine how tiny like think about how tiny your cells are and then in the inner membrane of the mitochondrion is this little enzyme and there are you know millions of them in each cell okay what is fermentation fermentation happens when there's not enough oxygen present and there are several different products that can occur but in in us in animals it's lactic acid also called lactate so you can see that if there aren't enough oxygen present those two pyruvate oops sorry those two pyruvate rather than going into the mitochondria and producing more atp instead what happens is that nad plus is going to get regenerated and lactic acid or ethanol are going to form so certain organisms are going to make alcohol as a product of fermentation certain others are going to make um lactic acid and this is what we make we make lactate or lactic acid okay so this is what when you start doing anaerobic exercise so you exercise to the point where your muscles are not getting enough oxygen anymore lactic acid is what causes your muscles to burn it's also it causes the soreness the next day after a really hard workout best way to move that out of your muscles is to exercise again and move that back into your bloodstream but so lactate also called lactic acid that's the product of fermentation that is anaerobic respiration respiration without enough oxygen present so that means if there's not enough oxygen present how many atp can you make for every glucose only two so when you're doing anaerobic respiration you are burning glucose at an accelerated rate you're exercising your muscles need atp they need that energy so you start burning glucose at a higher rate in other words you're burning calories at a higher rate because you're only producing 2 atp for every glucose instead of 36 on average for every glucose so the most you can produce in fermentation is to atp for every glucose we have a lot of products that are made by fermentation many of them you know so obviously beer and wine and other alcohols really you know all alcohol we drink is made by alcohol fermentation where ethanol is produced even rubbing alcohol acetone vinegar so anything that's made with vinegar including pickles soy sauce kimchi kombucha all those fermented products are you know fermentation means anaerobic respiration and that alcohol is getting produced or lactic acid and there are some other chemicals that can get produced depending on the type of bacteria that are carrying it out so certain bacteria and certain yeasts can give us different types of fermentation so yeast produce alcohol fermentation so that's how we get beer and wine and other forms of alcohol that we drink is from yeast fermentation so they would be producing ethanol as a byproduct of that fermentation also important to note that you can use other organic molecules to carry out cell respiration it's just not as efficient the cells prefer carbohydrates those inter glycolysis fats and proteins enter cell respiration at a later stage and there is a cost associated with that so it's not the healthiest way to carry out cell respiration the healthiest way is from carbohydrates but just wanted you to realize you can use fats and proteins but they come at a cost to the cell so carbohydrates are the preferred fuel for the body to produce atp okay that is cell respiration please make sure you can answer all of the questions on the study guide or the separate worksheet so depending on when you're watching this video you might have a separate worksheet or you might have those questions just as part of your study guide if you're not sure which one be sure to ask