pleasant day to everyone in behalf of sir aristotle vega this is kenneth fries and our lesson for today is about cellular respiration before we start the lesson let's take a look at these two cells the animal cell and the plant cell if you notice when you inspect their structures you can see there they have differences and they have similarities for example the plant cell has cell wall and it has these structures called larger vacuoles as compared to the animal cell which has smaller vacuoles and the animal cell only has cell membrane but both of them have membrane-bound organelles and one of these membrane-bound organelles that is related our lesson is this called the mitochondrion and you should we will also focus on the [Music] cytosol which is found in the cytoplasm because this this two parts this this organelle called the mitochondrion in the cytoplasm both play an important role in cellular respiration if we focus on this organelle mitochondrion you'll notice that it has similar structure to the chloroplast of the plants because the mitochondrion has two membranes so there's the outer membrane this is the outer membrane then there is what you call the inner membrane so this means that the mitochondrion has two membranes and between those outer and inner membranes it's called the inner membrane space now inside the inner membrane there's a fluid filled structure here here called the matrix this one this is the matrix and just in the inner membrane you notice that the inner membrane of the mitochondrion is folded so they they contain false so these folds are called cristae so you need to remember these basic parts in the structure of the mitochondrion because they are very important in the process of cellular separation aside from the cytosol which is located in the cytoplasm now for the lesson let's define first what is cellular respiration so cellular respiration is a process which it breaks down sugar molecules so usually it's in the form of glucose and this glucose acts like a fuel in order for the cell to assemble atp or adenosine triphosphate molecules now this atp molecule is very important because it is the one that stores what we call the chemical energy in the form of covalent bonds that can be used by the cell for its cellular activities this is the general chemical equation which is a balanced reaction of the cellular respiration so in this it states that one glucose molecule will combine with six molecules of oxygen so these are called the reactants and the product is six molecules of carbon dioxide and six molecules of water these are the products and if you notice if you reverse this reaction it's what we call the photosynthesis so cellular respiration is the reverse reaction of photosynthesis now in cellular respiration remember there are four major stages in some books there are three major stages but uh here we will discuss the four major stages so included the link reaction so what are these four major stages first is the glycolysis and you have to remember the it is the very first stage of cellular respiration whether it's aerobic or anaerobic so glycolysis happens in the cytosol which is in your cytoplasm then after glycolysis there's what we call the link reaction which happens inside the mitochondrion in the matrix and this is very important because the from because the link reaction from the term itself it blinks the glycolysis and the krebs cycle so link reaction is important because it processes the products of glycolysis so it can be used in the krebs cycle and krebs cycle is the third stage which also happens inside the mitochondrion specifically in the matrix this kreb cycle is also known as citric acid cycle or tca or tricarboxylic acid cycle and the last stage which produces lots of atps as compared to the previous ones are is what we call the electron transport chain and this also happens in the mitochondrion but in the inner folds of the inner membrane called the cristae as you can see here the illustration in the illustration so glycolysis happens in the cytosol so it is outside the mitochondrion and then the next is what you call the link reaction together with krebs cycle and then which happens in the matrix and then in the crystal or the faults of the inner membrane is where the electron transport chain happens so let's start with the first stage of cellular respiration which is called glycolysis glycolysis when you look at the term glyco means sugar and lysis means to break down so generally it's a process of breaking down sugar or splitting sugar so that sugar is in the form of glucose and it happens or it occurs in the cytoplasm specifically in the side soil so in this process the simple sugar which is usually in glucose and it contains six carbons they are split into two so six divided by two is three so that means each uh split molecule contains three carbon molecule okay so each molecule contains three carbons and they are called pyruvate now the splitting process of glycolysis requires 2 atp it's like an investment and then it with the help of some enzymes and some nucleotides in the form of nad plus so these are the things that are required for the glycolysis to occur and remember this process produces a total of two net atps so when you say net atp you have to deduct the one that you have used because uh when you compute for the gross atp or the total atp is produced in glycolysis it's four but you have to subtract the two atp initially used so that means glycolysis could produce a total of two net atps now the details we'll discuss on the next slide so this is how glycolysis happens so remember glycolysis is the very first stage of cellular respiration so it happens in the cytosol in your cytoplasm of the cell now there are two basic phases happening in glycolysis first there is what they call the energy investment base what is this energy investment phase in order for the glucose to be split into two molecules there is a need for the participation of two atp molecules as you can see here so these two atps are already available uh before the glycolysis even starts so what happens here is that the atps will give each atp will give their phosphate to the glucose and that atp will be converted into what you call adp or adenosine diphosphate a low energy molecule and as you can see here the glucose molecule is transformed into another form it's called fructose 1 6 by phosphate but it still contains six carbons if you count this is still six it only has uh six uh two phosphates at both ends and then eventually this fructose one six by phosphate will split with the help of an enzyme called aldolase and then it will become what we call these two molecules this is snatched pyruvate this is what they call g3p and dap glyceraldehyde so this is glycoaldehyde three phosphate and the other is dap also known as dihydroxyacetone phosphate the details here will be discussed on other subjects in biology which is more advanced when you discuss biology but basically this g3p and dap each contains three carbon three carbons in its molecule now what happens next is that this two molecules the g3p and the ap will be further transformed so with the participation of this molecules the nad if you remember nad is capable of receiving electrons so it's an electron carrier what will happen is that the nad will interact with this two molecules and what will happen here is that they with the help of nad they will attach additional phosphate at the ends of this molecule so this one will attach here and in the process they will get electrons and this process is called oxidation because the molecules lose electron so what happens here as you can see in the next illustration the nad will become nadh that means it already carries electron and then you notice the transformation in these two three carbon molecules and then this is what we call the energy harvesting phase wherein the glycolysis will already make atp so what happens here is that the phosphates that are attached this phosphates that are attached to these three carbon molecules we'll uh uh so here that it's not here first in this uh diagram so this phosphates here will attach to the adp molecules that are present in the cytosol so once they combine the adp and the phosphate this adp will be transformed into atp so that's the energy harvesting phase so in the process of glycolysis as you see here there are four atp molecules that could be produced in the process of glycolysis and as a result of that the g3p and the dapv4 will become what we call pyruvate so this is the end product of glycolysis so it produces four atp molecules and then nadh and then pyruvate now remember pyruvate comes from the glucose which is which was split a while ago and it contains three carbons so as the result the products of glycolysis are two net atp so when you say 200 atps so the four that has been produced before you will subtract the the two atps that you have used in splitting glucose or the in the energy investment phase so that means the two that will remain is the two net atps and then it will also produce two pyruvates which is composed of three carbons so it is important to count the carbons here in this process and two nadh so this nadh carries what we call the electrons they are electron carriers now after glycolysis these two pyruvates so these two pyruvates which contain three carbons they have two possible pathways now in this in the case of the absence of oxygen that those two pyruvates will undergo what you call an aerobic respiration or in other terms it's called fermentation that happens if there's no oxygen and that means the pyruvate will still stay in the cytosol so in that case in in the absence of oxygen this pyruvate molecules will be further transformed into two possible forms first is the lactic acid which is uh in human human cells this is the one that's being produced in anaerobic respiration lactic acid and we usually experience this if you're let's say you suddenly engage in a strange activity like sports or exercise without proper warm-up that means there's not enough oxygen being received by your cells so that means your cells are forced to carry out what you call anaerobic respiration and the other possibility is that the pyruvate could undergo the transformation into alcohol in the form of ethanol and this ethanol also produces carbon dioxide and the purpose of this anaerobic respiration since there is no presence of oxygen it just converts the nadh which carries the electron back to nad plus so it's just a way to keep the glycolysis going in the absence of oxygen but in the presence of oxygen then aerobic respiration will happen after glycolysis so this is with oxygen so that means the pyruvate molecules will then enter the mitochondrion the matrix of the mitochondria so let us assume that there's a presence of oxygen so we'll proceed to aerobic respiration but remember glycolysis is the starting point of respiration whether it's an aerobic or aerobic okay so in the next stage since we're now in aerobic respiration we assume that there's a presence of oxygen so after glycolysis so so this is the illustration here uh glycolysis two pyruvates if no oxygen fermentation was still in the cytosol and then if there's oxygen straight to the mito country on in the matrix now once there is a presence of oxygen the pyruvate molecules remember pyruvate contains three carbons they will enter the matrix of the mitochondrion so you remember the matrix then inside that matrix the pyruvates will undergo what they call the link link reaction or intermediate reaction now what happens here is that these two pyruvate molecules here will interact with the molecule nad plus so nad plus is an electron carrier and remember these electron carriers are very important in the succeeding stages of cellular respiration so what will happen here is that this nad will split or will remove one carbon from each pyruvate thus reducing the pyruvate into two carbon molecule here and then the carbon that is being split will become what you call carbon dioxide and you know that carbon dioxide is a waste material it will be brought out of your body through your respiratory system and the result of that the nad will be transformed into nadh that means it already has electrons in it then this uh two carbon molecule which previously is pyruvate will attach to a molecule called coenzyme a and then it will produce what we call acetyl oa so here are the products of link reactions after the link reaction so the purpose of link reaction is to prepare the pyruvate to become a form in which it can be used for the next process which is the krebs cycle so the products of link reaction are the following since there are two pyruvates it will produce two carbon dioxide which will be brought out of the body as waste material and then the nadh will just stand by for the succeeding process that will follow and then these two acetyl-coa they are called acetyl-coa molecules because it's a coenzyme a attached to two carbon molecule these are the ones that will be used in the next process so the next stage is what they call the krebs cycle also known as citric acid cycle or tca cycle by the way tca stands for tricarboxylic acid it's just the iupac name of citric acid cycle and it's also named as krebs cycle uh because it's uh based on the name of the scientists who discovered the mechanism of the cycle hand scrubs okay so there are three possible names of this cycle and this also happens inside the mitochondrion in the matrix so as we have said before the acetyl-coa which is already a prepared form of molecule to undergo krebs cycle it's in this form it contains two carbons so i want you to focus here on the number of carbons so acetyl-coa has two carbons then it will combine with the molecule present in the matrix called oxaloacetate so which is made of four carbons so you just have to add two plus four is equal to six and then the coenzyme a will be released and this will result in the formation of a new molecule called citric acid and this is the reason why it's called citric acid cycle but please take note in the kreb cycle or citric acid cycle although it is called citric acid cycle you have to remember that the starting and ending molecule in this process is oxaloacetate so please remember that but it's still called citric acid cycle because it is the first product produced in the process so oxaloacetate which has four then you add it to two carbons between produce citric acid or tricarboxylic acid and then what happens next so it remember these six carbons then nad will interact with this which will it will get electron so that means the citric acid will be oxidized that means it will lose electron and give it to nad and then this nad will become nadh and what will happen here is that the nad will also split or cut one carbon and that carbon will become carbon dioxide as well as a waste material then you notice from six carbon it will become five carbon uh five carbon molecule then the next step another nadh will interact again and again cut one carbon from this five carbon molecule so the names of these molecules will be further discussed in senior high school in in further studies in biology so it's just you i want you to focus on the number of carbon so it started with six and then reduced the five so the result of this it is you produce electron carriers and then from five it will be reduced to four so what will happen to the one carbon it will become also carbon dioxide and thus producing another nadh and then this four carbon molecule will fir will be further processed we'll interact with the following substances the adp and the inorganic phosphate which will be transformed into atp so that means krebs cycle is also capable capable of producing atp and then it will also further encounter nad and then the casino of nad it's also an electron carrier called fad or flavine adenine nucleotide they they will oxidize this four carbon molecule until it will be transformed back into oxaloacetate which still has four carbons so if you notice the pattern in krebs cycle four plus two is six and then you cut one carbon will become five then that carbon will be released as carbon dioxide and it will be reduced to four and so on okay so that means the krebs cycle will start with oxaloacetate and end as oxaloacetate but the first product that is produced is citric acid and it's the reason it's why it's called citric acid cycle so as an overview of that krebs cycle so that we could have you could have a better grasp so remember from the link reaction you produced two acetyl-coa molecules so remember two and then it will combine with oxaloacetate which which is which has four carbons so it will produce citric acid which has six carbons and then it will interact with nad which will produce carbon dioxide and nadh so that will reduce the six carbon to five and then this five carbon will further react to nad and will be further reduced into four carbon and that one carbon that is being split will also become carbon dioxide and then it will this four carbon molecule will undergo further processing or reconfiguration of its structure so it will interact with adp so that the krebs cycle will create atp remember this is the the the result of these cycles is production of atps and then furthermore it will still react with another electron carrier called fad or falavine adenine the nucleotide and it will become fadh2 or flavin adenine the nucleotide hydrogenase and then another with nad which should become nadh and then this four carbon will be transformed back into oxaloacetate so that is the krebs cycle so if you're going to get the bigger picture here it's just you add two plus four becomes six and then six will be reduced to five and then four so that's a cycle so that's the general process of krebs cycle but if for the details it has a different lesson a little more advanced biology cellular respiration in biology now remember uh since there are in one glucose molecule you produce two pyruvates into acetyl coa that means citric acid cycle happens two times okay remember that so one citric acid cycle for each acetyl coa molecules so after two citric acid cycles these are the products a total of four carbon dioxide six nadh so six electron transporters in the form of nadh and two fadh2 and then to atps if you notice in glycolysis you already produced two atps in the link reaction there's no atp produced in the krebs cycle you still produce two additional atps now you notice that the cell is already capable of producing atps but this quantity is not enough so it needs another process now remember this nadh and fadh2 which are electron carriers they are very important because they will proceed to the next part of the mitochondrion called the free state or the inner membrane the inner falls in the inner membrane for the next process which is uh popularly known as electron transport chain but actually this is technically known as oxidative phosphorylation because it's the process of combining phosphorus inorganic phosphate to adp to make atps and there's also an additional or or additional process here aside from electron transport chain it's also called chemismosis okay so if this is the mitochondrion after the krebs cycle which happens here in the matrix the electron carriers together with the oxygen will proceed to the false the cristae if you zoom this cristae you will see several structures here so it's similar to the light dependent reaction in photosynthesis there are also structures in the membrane the in the inner membrane so if in photosynthesis is in that in the thylakoid membrane here in cellular respiration in the mitochondrion it's found in the cristae or the inner membrane of the mitochondria and remember the region that separates the inner from the outer membrane is called the inter membrane space and this is also very important in the process now here this is the matrix now what are these structures so these are proteins so there are certain names for that so i'm not requiring to memorize but you have to be familiar these are called protein complex protein complexes so uh this is what will uh these are the structures that will participate in the process called electron transport chain and happens in the crystal so they have their names nadh dehydrogenase bikini cytochrome bc1 etc but you can simply name this as protein complex one and this is protein complex two this is protein complex three and four and this fifth one is the atp synthase you're familiar with the atp synthase it is capable of producing atp when it turns like a turbine now these structures here that you begin on in the cytochrome c they are electron transporters so they are capable of fetching electrons from one protein complex to the next protein complex so so that's uh what you need to remember now how does electron transport chain how does what's its mechanism how does it happen so there are remember electron transport chain is a simultaneous event there are lots of events happening at the same time so let's try to get into it so electron transport chain so these are the uh the first things that will happen first remember there are two electron carriers the nadh and the fadh2 what will happen is that they will go to this protein complex one so nadh will go to protein complex one and fadh2 will go to protein complex two and what will they do is that they will donate their electrons there so they will donate their electrons so what will happen to nadh it will be transformed back to nad and the fadh2 will be transformed back to fad okay so nadh will become nad fadh2 will become fad so what happens there is when the electrons are being donated to this protein complexes here the electron transporters will fetch them so as you can see here this electron transporter has already fetched and it will bring the electrons from one protein complex and to the other and so this this electron transporter it will also trans uh fetch and transport the electrons from one protein complex to another along the crystal or the inner membrane and that's the reason why it's called electron transport change it's like a chain of events now as a result of that while transferring electrons there is an attraction happening like in photosynthesis if you see the arrow the hydrogen ions or the protons that are present in the matrix are attracted and will go towards the inter membrane space here so that means there is an accumulation or an increase in amount of protons in the inter membrane space so these protons are also known as hydrogen cations and due to that it will increase the positive concentration gradient or the charge inside the inter membrane space and if that happens the accumulation of this concentration gradient will force a process called kemi osmosis if you remember osmosis is the movement of water through a semi-permeable membrane but since this is chemiosmosis it's not water that's moving through a membrane it's the hydrogen ion so this hydrogen ions will undergo a process of chemismosis and it will pass through the atp synthase so remember the atp synthase once hydrogen ions passes through the atp synthase this atp synthase will turn like a turbine and it will carry out a process called oxidative phosphorylation so oxidative phosphorylation is a process where in the atp synthase is activated and then the adp which is present in the matrix will combine with inorganic phosphate and that process is called oxidative phosphorylation and thus this adp plus inorganic phosphate will produce what we call an energy molecule atp so that's how it goes so as the electron transport chain is happening due to the donation of the electrons from electron carriers the electrons are transported by by transporters through the process of electron transport chain therefore it increases the movement of ions in the inter membrane space thus increasing the concentration gradient and it leads to a process of chemismosis which brings the hydrogen ions back to the matrix through the atp synthase and in turn the atp synthase produces atp but as this happens you will notice that the electrons that are being fetched by the electron transporters will accumulate in this protein complex so this is a protein complex one two one two three protein complex four so in protein complex four the electrons will accumulate there something must become an electron acceptor and that's where the oxygen comes in so this is the importance of aerobic respiration the presence of oxygen molecule this oxygen molecule will act as the final electron acceptor in the process of electron transport chain so this electrons here will combine with this oxygen molecule together with hydrogen ions and this oxygen molecule will be transformed into water molecule and water molecule is one of the products of cellular respiration so that means one oxygen molecule plus four hydrogen ions plus four electrons will produce two molecules of water so that means uh as eight lots of atps are produced through the process of oxidative phosphorylation water is also produced because of the action of the accepting the oxygen molecules accepting the accumulated electrons in the electron transport chain and because of this the total uh the accumulation or the simultaneous events that are happening in the electron transport chain it produces about 32 to 34 atps or it depends on the literature some say 34 36 32 but it's about 32 to 34 atps and about six molecules of water that's per glucose molecule that is being processed in cellular respiration okay so it still depends on the number of glucose so the more glucose you just have to multiply okay so this is per glucose molecule so that is the product of the electron transport chain and if you notice as compared to the previous stages the electron transport chain is capable of producing large quantities of atps due to the action of this electron plant electron carriers nadh and fadh2 that was an overview of the overall aerobic cellular respiration process we're talking about aerobic because we assume that there's a presence of oxygen so once you eat the food and it's being fully digested so that carbohydrates will be broken down into smaller molecules called glucose it will enter your cell and once it is in your cytoplasm in your cytosol then the glycolysis will happen so what happens in glycolysis it will split that glucose molecule or it will split the sugar and in the process it produces two net atps now if there's a presence of oxygen it will undergo what you call link reaction or it's also known as oxidation of pyruvates so remember glycolysis produces two atps and it will also split the glucose into two and you call this these two molecules pyruvates and this pyruvates will be processed in link reaction here and then once it be it's transformed into acetyl coa it will undergo what we call citric acid cycle we shall further process this acetyl coa into carbon dioxide which will be released out of the body and then it in the process it will produce two atps now after that the electron carriers nadh and fadh2 that are produced in the citric acid cycle will proceed to the cristae to the to the folds here which contains the protein complexes and the atp synthase and they will perform what they call the electron transport chain which will produce at about 32 more or less 30 to 80 piece so that means of all the three stages it is the electron transport chain that is capable of producing lots of atps now how is that computed so there are different literatures available but we have this as an example so how is that computation of atps carried out and how did they figure out the number of atps produced in etc or electron transport chain so based on experiments or studies by researchers they have computed that about four hydrogen ions remember the hydrogen ions are the ones that are are passing through the atp synthase through chemismosis four hydrogen ions are needed to produce one atp so that means the four hydrogen ions needs to enter the atp synthase to produce one atp and also based on their studies one nadh that electron carrier can produce up to three atps okay so the details here will be discussed in more advanced biology topics and one fadh2 can produce about two atps so if you're going to tally the molecules being produced in each stage of the cellular respiration so it's uh remember this is per glucose molecule so we assume it's one glucose molecule so in the process of glycolysis two net atps are produced and to nadh fadh2 is zero now the next stage the link reaction no atp is produced then but it it's able to produce two nadh and no fadh2 in the krebs cycle it is able to generate 2 atps 6 nadh and 2fadh2 so if we get the total the total atp is produced in the first three stages are four net atps remember we already deducted the 280 pistols in the energy investment phase and when it when we compute the total nadh produced in the three stages total of 10 nadh and then fedh2 a total of two fadh2 molecules so we are talking here about the products produced per glucose molecule then we have to compute since one nadh is capable of producing about three atps and there are 10 nadh produced so 10 multiplied by 3 is 30 atps then since there are two fadh2 molecules produced in the three first stages so in the electron transport chain this two fadh multiplied by two is four so 30 plus four so there are about 34 atps that are produced from oxidative phosphorylation or in the electron transport chain plus you add the four net atps okay that are produced in the previous cycles the glycolysis in the kreb cycle a total of a maximum or about 38 atps are produced in the overall process of cellular respiration specifically aerobic cellular respiration so the summary of the chemical reaction as we have shown a while ago in the previous slides so one glucose molecule together with six molecules of oxygen will produce six molecules of carbon dioxide the swiss material and then six water molecules it's happening remember it happened in the electron transport chain and about and due to that overall process it's able to assemble about 38 atp molecules so that's how the computation of atps are done now if remember that these are just estimates because uh these are based on experiments so different literatures have different uh recommendations or or or they have different discussions about this um some legit literature say that uh there's a reduction in atps because uh i have read some that in order for the atp to go out of the mitochondrion and be used by the cell there there is uh like it there is a need for a consumption of 2 atp so that will reduce 30 to 36 so it really depends on the on the literature or the references so but it's about 30 plus 32 34 36 or 38 maximum of 38 atps are produced in the process now as a summary of cellular respiration to remember that cellular respiration is breaking down of sugar to make atp now cellular respiration always starts with glycolysis whether there's presence or absence of oxygen glycolysis is the starting point and glycolysis happens in the cytosol which is the fluid in your cytoplasm in the case of the absence of oxygen these pyruvates that are produced in glycolysis they remain inside in the cytosol and it will undergo what we call an aerobic respiration also known as fermentation and that's the reason why when in making bread it's uh there's a fermentation involved there because there is ethanol produced and carbon dioxide produced so that's fermentation in humans we have what you call lactic acid formation but with the presence of oxygen these pyruvates which are produced in the glycolysis will proceed to the matrix so that it could undergo what we call the link reaction which will prepare the pyruvates to become acetyl coa and used in krebs cycle also known as citric acid cycle or tca cycle now next the electron carriers the nadh and the fadh2 are very very important because these electron carriers together with oxygen will proceed to the cristae or the inner membrane folds of the mitochondrion for them to perform what they call the electron transport chain and this electron transport chain could just will result in the following events the increase in concentration gradient then chemical osmosis and oxidative phosphorylation so this oxidative phosphorylation will lead to production of lots of atps and last as a general balance reaction so that means one glucose molecule needs six molecules of oxygen so that it could process the cellular respiration properly and produce six molecules of carbon dioxide six molecules of water and about 36 up to 38 atps or adenosine triphosphates which are energy molecules used by your cells to perform cellular activities so i hope you understand the lesson and that will be all thank you very much [Music] you