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0:06
Hey everyone! Dr. D. here, and in this video we're gonna be covering chapter 7 or at least part of it. Let's see how far we get! Chapter seven covers cellular respiration, a very important process by which our bodies, our cells, are able to make ATP by burning sugars mainly and also there's a process for fats as well but we're mainly going to be focusing on how sugars get burned in our cells in order to produce ATP. And remember ATP's very important energy currency of the
0:40
cell through energy coupling cells can do many things using ATP molecules to power those endergonic processes and also will touch on fermentation as well. which which is like an offshoot of cellular respiration it's a off-ramp I'll I'll explain that a little bit. So, what is cellular respiration? Cellular respiration is again the process by which our cells can use the energies from mainly sugars but fats as well and couple that with
1:13
oxygen here's the equation here sugars and oxygen are used by our cells to produce mainly ATP right? ATP is the energy currency of the cell and the waste products CO2 and water okay? Technically one glucose molecule will use up six oxygen to produce six CO2 waste molecules, six water waste molecule, and ATP. In eukaryotes you are going to net 30 ATP and in prokaryotes you net 32 ATP and I'll explain why that difference is there in a little bit. Okay,
1:58
so you get a lot of energy out of a glucose molecule, enough to make a bunch of ATP and cellular respiration is the process by which we do this inside of our cells and remember in eukaryotes we have mitochondria. In grade school you learned that mitochondria are the "powerhouse" you know they that's what they call it the "powerhouse of the cell" well, in the in the mitochondria is where majority of that ATP is being made by breakdown of
2:33
sugar all right? Now, what I want you to do before we actually... before you actually proceed with this video, I want you to do this for me and it's gonna make this video- it's going to allow this video to make a lot more sense! I want you to watch this video here you see the one I'm outlining. Click this icon watch that video it's a short three-minute video on the importance of cellular respiration and the big picture of cellular respiration
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and then I want you to skip to this slide okay see what I'm doing? Skip to this slide and watch this video as well click this icon that I'm outlining right now or circling right now click this icon to watch this video as well I guarantee you this will help you understand this chapter and if I were you I would watch both of the videos I just pointed out before I actually watch this video because those those videos that I had put together and
3:39
are gonna make perfect sense of this this video here. So, I wouldn't just jump right into this video. I would watch those videos first okay now let's say you've watched those videos welcome back again! The process of cellular respiration- you're taking sugar - in this case in the form of glucose six oxygen reactant to produce six CO2 six H2O and most importantly ATP. Again 30 net ATP for eukaryotes 32 for prokaryotes. During this process
4:15
there is a number of oxidation and reduction events that are going to occur. Remember oxidation is the loss of electrons and reduction is the gain of electrons? Well, the the story of cellular respiration is a story of oxidation and it's a story of reduction so there are several what are called redox reactions - reduction/oxidation reactions and there's basically a journey of electrons those electrons start on sugar or on fat. Those electrons
4:52
make their way to electron acceptors. They make their way to other electron acceptors, and ultimately they make their way to oxygen now I'm gonna explain all of this shortly, but just understand that the process of cellular respiration is the story of oxidation and reduction so do familiarize yourself with that term. Oxidation is loss of electrons, while reduction is gain of electrons. Just remember that. Here's a review this is just a review. If you have
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sodium and chlorine they react to form sodium cation and chlorine anion that means sodium lost an electron, it became oxidized. And chlorine gained an electron it became reduced. So, anytime something becomes positively charged it becomes oxidized that lost an electron and then anything that gains the electron becomes reduced. Just remember that. These terms you don't need to know I think I've removed this from the exam, but just for your own information, the
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electron donor is called the 'reducing agent', whereas the electron receptor is called the 'oxidizing agent' again this is kind of counterintuitive, so I've removed this from the exam but just for your own information it's there. So, what's happening in the process of cellular respiration? Look, you've got glucose okay? You've got sugar. Sugar's getting oxidized to CO2 so, real quick, bear with me on this- what is sugar sugar? It's C6H12O6 right? That's glucose, right? What's
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glucose made out of? It's made out of carbons, hydrogens, and oxygens, right? Well, what would happen if you took its hydrogens away? If you took the Hs away from glucose what's left? If I take the Hs away? Carbons and oxygens right? And that is CO2! And that's exactly what happens during cellular respiration. Did you see that? Glucose loses its hydrogens and so they say it becomes oxidized, you know why? Because if you take hydrogens away from glucose you're
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essentially taking electrons away from glucose. You're also taking protons away from glucose, but we're not talking about the protons from the glucose we're talking about the electrons. We are mainly focused on the electrons right? So, if you take H is away even though you're taking protons and electrons away it's still considered oxidized because you are taking electrons away from the sugar if that makes any sense. So, when you steal
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hydrogens from sugar yeah because you're also stealing electrons, sugar is considered oxidized to CO2 okay? CO2 is what's left of your sugar after you've stolen all of its electrons, or not all of its electrons, but the ones that are easily stolen. So think about this... when you breathe out, when you exhale, you breathe out, you're breathing out a lot of CO2 okay and your body produced that CO2 and your body produce that CO2 from the sugars and the fats inside of your cells inside of your
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body which is fascinating if you really want to think about it.Those sugars and fats that were weighing down your body they leave your body as mainly CO2 also some water. But let me explain that, where do you think those Hs end up, those electrons end up, from the sugar if you're gonna take the Hs away from the sugar you're gonna give them to oxygen. Oxygen is highly oxidative right? Oxygen is very electronegative- it loves electrons so glucose loves to donate
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electrons and oxygen loves to take up electrons. So, oxygen gains those electrons oxygen gains the whole hydrogen two hydrogens to form water you see. So, oxygen picks up the electrons to become water so it becomes reduced so what you need to know for the exam? Sugar glucose becomes oxidized to CO2 and oxygen gets reduced to water and of course what's what's the main product we care about in this process? ATP! Remember 30 net ATP for eukaryotes 32 for prokaryotes. Okay, now here's the
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thing you need to understand, you're not giving the electrons, these hydrogens, you're not giving them directly to the oxygen all right in cellular respiration the electrons start on sugar at the very beginning and they end on oxygen at the very end. But, that doesn't mean that these H's these electrons jump directly from the sugar to the oxygen. No, in fact remember how I said that this is a story of a number of redox reactions? A number of reduction
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oxidation steps? So, what's gonna actually happen is these hydrogens are going to be given to what's called an electron carrier and then the electron carrier hands the electrons to the electron transport chain and then the electron transport chain hands those electrons to oxygen did you follow that the electrons start on glucose they get handed off to electron carriers the electron carriers hand them off to the electron transport chain and the electron transport chain
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at the very end hands those off to oxygen to make water did you follow that the there's a there's a number of redox reactions okay here's here's one of those electron carriers now the nicotinamide adenosine dinucleotide or nad plus nab plus is a electron carrier another electron carrier in this process is called fa d okay and those electron carriers look like this look here this is the electron carrier NAD+ both of the electron carriers NAD+
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and fa d are die nucleotides you know what a nucleotide is right we learned in chapter 3 a nucleotide see what I'm circling here a nucleotide is a building block of DNA or RNA you see so you got a phosphate group a five carbon sugar and a nitrogenous base well what's it died nucleotide it's basically two nucleotides okay you don't need to know the the structure of this I just have this here for your own information but I wanted you to know at least the general
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structure of these electron carriers and that they are die nucleotides so what did the electron carriers do they pick up electrons essentially hydrogen's which is more than just an electron but they call up just electron carriers even though they carry electrons and protons they're called electron carriers the the well the electron carriers pick up electrons and protons and become reduced okay and then they can carry those electrons and protons they can carry
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them to the electron transport chain that's what's going to happen here so for example this is the oxidized carrier called nad plus C this is the oxidized carrier nad plus it can pick up two electrons and one proton to become NADH you see nad plus has a positive charge but if it picks up two electrons and a proton it becomes NADH okay nad plus accepts two electrons on one proton to become NADH now it picked up the H so think about it like this think about it
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like this remember when I said where did those HS go from glucose for example where'd the H go the H goes to the electron carrier making it from NAD+ to NADH okay and then the electron carrier will carry those H's those electrons essentially to the electron transport chain and then the electron transport chain will hand them off to oxygen to make water okay and here's how it works you can see here this is the process of D hydrogenation
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which means losing hydrogen's you see some enzymes come in take sugar or whatever energy molecule were talking about sugar or some derivative of sugar they also bind to the nad Plus which is the oxidized electron carrier and then you have the enzymatic reaction you have the HS transferred from the sugar to the carrier you see two electrons on a proton get transferred from the sugar or the high-energy derivative of the sugar to the oxidized carrier so now you form
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NADH si NADH and there you go so that's how the H's went from the sugar to the carrier and now the carrier can carry those H's carry those hydrogen's which is remember hydrogen is a proton and an electron carry that to the electron transport chain to power the electron transport chain and if you watch that video I told you told you to watch before this one you know that it's those electrons flowing through the electron transport chain that are going to power
14:24
the electron transport chain so did you see what happened let's say this is glucose this energy-rich molecule is glucose glucose would give its electrons in the form of hydrogen's to the nad plus carrier now that those electrons are on the carrier the carrier will carry those electrons to the electron transport chain giving the electrons to the electron transport chain and then those electrons go from complex 1 to 2 to 3 to 4
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powering the pumps to pump the protons the protons form a high concentration gradient those protons flow back in through chemiosmosis spinning the ATP synthase to produce ATP all right so that's the how the process works I remember so NADH by the way NADH drops off at complex one fadh2 drops off at complex - all right we'll get there we'll get there I'll explain this in more detail soon so what is an overview of cellular respiration cellular
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respiration it actually consists of three and a half stages that you need to know about the video that I had you watch before this video here if you if you like on this video here this icon at the bottom left click on that that explanation refers to this oxidative phosphorylation which is stage 3 I explained cellular respiration from the end or kicked my way back to the beginning so stage 3 is oxidative phosphorylation it's where 28 of the 30 or 32 ATP are
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made it's very very important that's where ATP synthase does its job all right but the other stages are called stage 1 glycolysis stage 1 and 1/2 oxidation of pyruvate stage 2 is the citric acid cycle by the way you might want to write in your notes here citric acid cycle aka Krebs cycle aka TCA cycle they those all mean the same thing by the way you might want to keep track of that in fact please know that that these three things
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mean the same thing and different textbooks adopt a different definition or different title but they all mean the same thing so we're going to talk about stage 1 we're gonna talk about stage 1 and 1/2 we're gonna talk about stage 2 and we're gonna have to talk about stage 3 and you could see the overview here this is a wonderful overview of the entire process that I have been talking about ok you could see stage 1 right here this is
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glycolysis ok and by the way glycolysis notice right here you have a picture of the inside of a cell and then this yellow kidney bean-shaped thing here is the mitochondria notice that glycolysis it does not happen inside of the mitochondria does it glycolysis happens in this cytosol the fluid part of the cytoplasm alright and glycolysis is step 1 and then after glycolysis the products of glycolysis go into the mitochondria for
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step 1 and 1/2 pyruvate oxidation then on to stage 2 citric acid cycle aka Krebs cycle aka TCA cycle and then off to stage 3 for oxidative phosphorylation ok stage one one and a two and three and the reason I say this is a wonderful overview slide is because you can see all of the products and reactants for all the stages on this slide again glycolysis happens in the cytosol you start with glucose which is a six carbon sugar you end with two
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pyruvates two pyruvate which are two three carbon sugars you form two ATP through a process known as substrate level phosphorylation which I'll explain in a little bit for you but you form two of your ATP here and you form two NADH here as well and what does NADH do remember NADH means that the hydrogen's from the sugar were given to nad plus to form NADH so both of these NADH are on their way to the electron transport chain you see this arrow across the top
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that means that the NADH are on their way to the electron transport chain to drop off those electrons and power the proton pumps power the electron transport chain okay then at the end of glycolysis these two pyruvates move in to the mitochondria by the way this is a process that costs two ATP to get these two pyruvate into the mitochondria you're actually going to use two ATP so this is why they say in eukaryotes we net only 30 ATP because 28
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plus 2 is 30 ATP and by putting the pyruvate into the mitochondria it costs 2 ATP so you only netted 30 not 32 ATP but in prokaryotes do you have a mitochondria to do this with do you have a mitochondria to put the pyruvate in - no in prokaryotes you do not have a mitochondria so you don't have to invest the two ATP to get the pyruvate into the mitochondria anyway just in case you're wondering why exactly prokaryotes at 32 ATP whereas eukaryotes only 30 ATP
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that's why okay then by the way we're gonna we're going to go into each one of these steps in more detail a little bit but this is just an overview then during pyruvate oxidation your pyruvate is get oxidized which means its electrons are going to go to more carriers to make two more nadh which go off to the electron transport chain to drop off those electrons and you form two what are called acetyl co a as well the asila co a go into the citric acid cycle
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however 2 co 2 are also made to SiO 2 by the way why was the co 2 made let me explain glucose is a six carbon sugar right glucose is a six carbon sugar you chop that in half during glycolysis glycolysis means sugar break you cut the six carbon sugar into two three carbon sugars called pyruvate those pyruvate going to the mitochondria and they become a silicon well as silicon you got two acetyl co a each one of them's only two carbons well where did the third
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carbon go on these of the pyruvates the third carbon leaves us co2 does that make sense you had six carbons and glucose you had six carbons and glucose that broke into two 3-carbon sugars called pyruvate those went into the mitochondria and got oxidized so you took more hydrogens away and now this causes the molecules to fall apart one carbon on each of those pyruvate sleeves as co2 leaving behind a molecule called acetyl co a two
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molecules called the civil co h which are two carbon molecules okay dose acetyl co a then going to the citric acid cycle which gets further oxidized to make 6 more nadh to fadh2 alright and it's going to release the the last four co2 so now you've released 6 carbons you started with 6 carbons so all of your glucose carbons have now left after being oxidized to co2 and you formed another 2 ATP through substrate-level phosphorylation ok but that's not the end of the story
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remember what are all the reduced electron acceptors going to do the nadh here the nadh year the nadh here the fadh2 here all of these reduced electron acceptors are coming to stage three they're coming to the last step oxidative phosphorylation to drop off the electrons in the electron transport chain those electrons spontaneously move through the electron transport chain remember NADH dropped off its electrons at complex one fadh2 drops off its electrons at complex two
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those electrons go on a journey down the electron transport chain and they power the pumps to pump protons okay and once the protons are pumped they form a high concentration of protons in the intermembrane space those protons force their way back through ATP said they spinning it to produce ATP and you're forming 28 ATP that way through oxidative phosphorylation okay 28 ATP and I'll explain the difference between substrate level phosphorylation and ATP
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from oxidative phosphorylation in a little bit okay so substrate level phosphorylation means that you're making ATP but look how you make it instead of taking just be just taking a phosphate group and sticking it on to ADP by the way ADP means diphosphate adenosine diphosphate instead of taking an inorganic phosphate attached into adenosine diphosphate to make ATP you're taking the phosphate group from an organic molecule so this green dot
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represents an organic molecule a molecule with carbons in it if an organic molecule has a phosphate group attached and you're taking a phosphate group from an organic molecule to attach it to ADP to make ATP that's called substrate level phosphorylation again substrate level phosphorylation is when you make ATP by taking a P a phosphate group from an organic molecule and just transferring the phosphate group to ADP to make ATP
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and that's what's happening during glycolysis you're making ATP that way and by Krebs cycle or citric acid cycle you're making ATP that way so because you're making ATP that way during these two earlier steps that's called substrate level phosphorylation remember at the end of the electron transport chain how did you make ATP at the end of the electron transport chain at the end of oxidative phosphorylation did you get those Peas did you get those phosphate groups from an organic
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molecule or did you get inorganic phosphate you got inorganic phosphate so because it was made during this process it's not called substrate level phosphorylation it's called oxidative phosphorylation because it required oxygen all right so before we start with glycolysis let me take a quick break catch my breath I'm gonna come back we're gonna talk about step 1 glycolysis and then we're gonna talk about stage 1 and 1/2 stage 2 stage 3 okay we're good
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we're gonna go into more details here so if you're confused at this point hopefully this clears anything up for you alright let me take a quick break I'll be right back with that information
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hey everyone welcome back from break time it is time to talk about stage 1 glycolysis glycolysis remember happens in the cytoplasm of the cell and it is the process by which you take glucose and you form two pyruvate to ATP through a substrate level phosphorylation and two NADH so let's talk about this it's a ten step biochemical pathway and here's how it works there's ten steps and you start with a glucose molecule and here you see the pink dots the pink dots
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represent each of the carbons in the glucose molecule so you got one two three four five six carbons and by the way glycolysis literally means sugar break glyco means sugar lysis means to break so you are literally breaking the sugar in half so eventually let me show you how we get there first of all the first steps of glycolysis are called the investment phase you take glucose and you're going to invest two ATP so you invest one ATP to phosphorylate glucose
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what does that mean look at this the sixth carbon on the glucose you give it a phosphate group where did the phosphate group come from it came from ATP that last phosphate the triphosphate that phosphate group is being given to glucose so now glucose is called glucose 6-phosphate you know why this sixth carbon of the glucose has a phosphate group attached that there's then an isomerization remember what isomer means slight change in structure into fructose
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6-phosphate so an isomerization results in fructose 6-phosphate and then you invest another ATP you hide you you phosphorylate phosphorylate means give a phosphate group to you phosphorylate fructose 6-phosphate into fructose 1 6 bisphosphate what does that mean now you started with glucose which is a 6 carbon sugar now you have a 6 carbon sugar called fructose and it has a phosphate on the first carbon and a phosphate group on the
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carbons the sixth carpet how did it get those phosphate groups it got them from ATP ATP has three phosphate groups two different ATP molecules donated one phosphate group each and those are the phosphate groups on the fructose sugar now you might be wondering well why why did we just spend ATP it looks like we're wasting ATP yeah I thought where the whole point of this is to make ATP well sometimes you have to invest money to make money right and in this case
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we're investing a DP to make ATP that's why it's called the investment phase we're investing two ATP to prime the pumps to get everything started okay so we can make more ATP to come now you might be wondering at this point oh gosh do I need to understand that glucose gets phosphorylated to glucose 6-phosphate then gets isomerized to fructose 6-phosphate which then gets further phosphorylated to fructose 1 6 bisphosphate this seems like a lot to
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remember dr. D and it is a lot to remember if you're gonna study for the MCATs or something like that you may want to go into that much detail but for my class you're not going to need to know nearly that much detail okay so don't worry what I want you to know is that you know yes glycol this is a multi-step process but you know the first few steps are an investment phase where you invested to ATP so far that's all you need to know besides the fact
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that glycolysis happens to the cytosol ok or cytoplasm okay now at this point look what happens the nicest part of glycolysis happens remember what lysis means break right so you gotta take your long three sorry six carbon sugar you see one two three four five six carbon fructose and you're gonna you know chop it in half you're gonna lie sit right glycolysis so you're gonna break that sugar in half okay now you have two three carbon sugars each one has a
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phosphate group attached right to three carbon sugars by the way there's that's why there's a column here on the left and there's a column here on the right cuz you chopped that sugar in half you have two three carbon sugars they parallel pathways so what that means is whatever is happening down this column is also happening down the other column okay those are identical so this three carbon sugar with a phosphate group attached is now called glyceraldehyde
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3-phosphate you have two of them you have two glyceraldehyde 3 phosphates and then what happens look what happens here if you look closely what's happening here what's happening here if you said ox oxidation you're right oxidation we're taking two electrons and a proton number we're taking two electrons and a proton from glyceraldehyde-3-phosphate we're attaching it to the oxidized electron acceptor nad plus to reduce it to the
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reduced electron acceptor NADH because remember how do you make NADH for my DV plus you hand it to electrons and a proton from the carbon source the energy-rich source which in this case is closed our aldehyde three phosphate so essentially what does that mean we just made two NADH how did we make two an IND eh we obtained two electrons on a proton from glyceraldehyde 3-phosphate great and what do these NADH go off and do right now do you remember what do
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these NADH go off to do right now well they are on their way to the electron transport chain to drop those electrons off into the electron transport chain does that make sense these NADH are off to the electron transport chain they will scurry off to find the electron transport chain in the mitochondria drop off those two electrons into the electron transport chain those electrons are going to go on a journey from complex one to complex
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two complex three complex for pumping protons out those protons reach high concentration outside in the intermembrane space those protons force their way back in spitting ATP synthase making ATP remember all that so that's what these NADH are going to go off and do just now so next what happens now you have two three carbon sugars called 1 3 bisphosphoglycerate why because another phosphate group was attached okay you don't need to know that and then look
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here's where the payoff phase happens the payoff phase now you're gonna take this phosphate group ah of this organic molecule this 1 3 bisphosphoglycerate you're gonna take this phosphate group off and hand it to ADP to make ATP isn't that substrate level phosphorylation remember what substrate level phosphorylation means taking a phosphate from an organic molecule such as a 3 carbon sugar attaching it to ADP to make ATP so this
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ATP was made these two I should say these 2 ATP were made through substrate level phosphorylation and then there's somewhere I saw organizations that happen and again you take the last phosphate group again through substrate level phosphorylation to make a further 2 more ATP so in some what happened you invested 2 ATP during the investment phase it's beginning and then you paid off for ATP during the payoff phase at the end so you invested - you made 4 so
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how many did you net well 4 minus 2 equals 2 you have 2 net ATP during glycolysis you need to understand that during glycolysis remember this year during glycolysis you make 2 net ATP through what process substrate level phosphorylation you also make 2 NADH nad plus was reduced to NADH twice right so you have 2 NADH and what did these NADH do they go out to the electron transport chain to drop off electrons and power the electron transport chain alright now
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what's left of your sugar at the end what's left of it it's now two three carbon molecules called pyruvate two 3-carbon sugars called pyruvate all right that's what's left of your original glucose molecule okay so again do you need to know every single little step here of the 10 steps of glycolysis no I don't expect you to know every single step what do I need you to know glycolysis happens in the cytosol or cytoplasm glycolysis involves investing
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two ATP and gaining for through substrate level phosphorylation so the net gain of ATP is two and what else did we form we form two NADH so to nad plus were reduced to to nadh and what else what was left of your sugar at the end your six carbon sugar is now two three carbon sugars called pyruvate alright that those are the things to know for my class okay again if you go into medical school or dental school and if they require you
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don't know glycolysis in more detail than that now you know the basis of it so you can go in to study it in more detail but for my class my reasons my purposes here I I want you to understand the concepts more than simply memorizing ten different little steps okay so that's all we need to know about glycolysis now now we have two three carbon sugars does that mean that we have taken all of the hydrogen's from these three carbon sugar have we taken
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every single electron that we can from this three carbon sugar the answer is no there's a bunch more hydrogen's that we could harvest that we could harness from those three carbon pyruvates sugars does that make sense because there's a bunch more hydrogen's that we could get there's a there's more steps that now we're moving on to stage one-and-a-half called oxidation of pyruvate remember stage one-and-a-half oxidation of pyruvate here's your pyruvate how many
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pyruvate did you have at the end of glycolysis the answer is two you had two pyruvate at the end of glycolysis where did those prior may go well those three carbon pyruvate go into the mitochondria and remember it takes an ATP to get each pyruvate into the mitochondria so you have to spend ATP to get the pyruvate into the mitochondria but once inside the mitochondria look what we do to the pyruvate we oxidize it right do you men on what oxidized means oxidation of
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pyruvate that means you're gonna take electrons from pyruvate not just electrons you're taking two electrons and a proton to make NADH you make one ndh per pyruvate but remember you had two pyruvate so you're gonna have two NADH in fact everything here is multiplied by two right remember if you ever in doubt go back to your summary slide here right during glycolysis you're one glucose became two pyruvate your to pyruvate going to the
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mitochondria to acetyl co a to co2 to nadh okay so this is your good summary slide here but let's go through that your to pyruvate your to pyruvate into the mitochondria to make to NADH release to co2 why are you releasing co2 do you think why do you release co2 well look this co2 is actually this carbon in the pyruvate this carbon and these two oxygen you see that and your pyruvate molecule which is a three carbon sugar the co2 that gets released is this C
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with these two O's so this carbon and these two oxygen are released as co2 so what's left now two carbons so your three carbon sugar is now a two carbon molecule called acetyl co a you see that your pyruvate which was three carbons is now a two carbon acetyl co a one of the carbons left into the atmosphere when you breathe out when you breathe out you released with that last co2 so two pyruvate become two co2 to NADH and the resultant molecule is called acetyl co a
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why is it called Co a well because coenzyme a which is a coenzyme we talked about coenzymes before coenzyme was attached to the two carbon sugar to make a silk away but again your three carbon sugar has now become a two carbon molecule so going and this is the summary of oxidation of part of you what do you need to know again your two pyruvate entered the mitochondria they're released to co2 to NADH and form to us it'll co a okay now did you
38:26
harvest all of the hydrogen's all of the electrons you can from acidic Oh a the answer's no not yet not yet and so that's why you haven't the next stage the next stage is called the citric acid cycle or aka the Krebs cycle aka the citric acid cycle you see this stage starts with acetyl co a okay you start with us it'll co a which is that two carbon molecule with the coenzyme a it acidic away enters the citric acid cycle and look it joins forces with another molecule in fact you may want to know
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the name of this molecule this is called a sallow acid II okay why is Excel OS 8/8 important well because oxaloacetate needs to be regenerated or replenished or remade although those mean the same thing remade at the end of the cycle oxaloacetate is read regenerated oxaloacetate joins up with a subtle code they literally bind to one another right with a covalent bond to form this big molecule called citrate did you see what just happened a silk away attached to
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oxaloacetate it lost its coenzyme component and it became this bigger molecule called citrate you know what another term for citrate is you guessed it citric acid did you see that citrate means citric acid do you see now why this is called the citric acid cycle because what was the first thing you created citric acid aka citrate all right you don't need to know the rest of these steps baby steps but let me tell you this citrate molecule is going to be
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oxidized right you're going to take its two electrons and protons away and hand it to the oxidized electron acceptor nad plus reducing it to NADH okay and what did these NADH go do that's right if you said go off to the electron transport chain you drop off those electrons you'd be right and look what gets released once you oxidize the molecule what's this that's released that's right co2 is released because think about it you got C's HS and O's and the sugar you start
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stealing those H's you start stealing those hydrogen's eventually everything else is going to break apart into co2 and that's what's happening you the more you oxidize the sugar the more you're gonna release its carbon so now you release co2 and then you oxidize it further make another NADH that NADH goes off to the electron transport chain releasing the final co2 so at this point all of your carbons from your original sugar molecule have released a co2 two
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of the carbons got released during ox datian of pyruvate four of the carbons got released during citric acid cycle okay and look here as a added little bonus at this step here you form some ATP with substrate level phosphorylation you made some ATP one per acetyl co a but remember how many acetyl co a that you have at the end of oxidation of pyruvate - so you had two acetyl co a so you actually get two rounds of the citric acid cycle or Krebs cycle you get
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two rounds of it per sugar right because each glucose gave you two pyruvate which gave you two acetyl co a this is just showing you what happens with one acetyl co a so you actually have two rounds of this cycle which means you make 2 nadh here 2 nadh here - co2 here - co2 here 2 ATP here with a substrate level phosphorylation substrate level phosphorylation then we still have more oxidation to do we oxidize the molecule further then this time we finally make
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fadh2 we reduce fa d to fadh2 by oxidizing the molecule and more more more modifications we oxidize the molecule further making another couple nadh here and we look what we do at the end of the cycle we replenish or regenerate oxaloacetate why so that it can accept the next incoming acetyl co a and do the cycle again so ok again do you need to know every single little step here no but do you need to know the concepts yes and that is that this at
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the end of the Krebs cycle or citric acid cycle or TCA cycle you have to regenerate this guy oxaloacetate because it will join up with us it'll go a to form citrate or citric acid citrate is then further is then oxidized to form 2 NADH here released to co2 here it's further oxidized to form another - said ADH here release another - co2 here it's then used to make 2 ATP through substrate level phosphorylation it's oxidized
43:24
to make 2f a th year and to nadh year and remember all of these nadh and all of these fadh2 are headed off to the electron transport chain to drop off those electrons to power the electron transport chain to make a lot of ATP during stage 3 okay so that's what we need to know and again you're like how do I remember all this what's a good overview I'll remember your overview slide here let me show you the good what do we just talked about we talked about
43:51
the citric acid cycle aka krebs cycle what'd I just tell you to remember for co2 are made to ATP are made by substrate level phosphorylation six total NADH are made and to total fadh2 are me that's what's important to understand and what had to be regenerated at the end of the citric acid cycle oxaloacetate those are the things to know so you don't need to know tons of it I'm just explaining in a lot more detail that you need to know again
44:18
during the citric acid cycle too acidic away enter they join up with oxaloacetate the thing that needs to be regenerated at the end of the citric acid cycle for co2 are made six NADH are made to fadh2 are made at two ATP is made by a substrate level phosphorylation and again remember the NADH made during glycolysis the NADH made during pyruvate oxidation the NADH made during citric acid cycle and the to fadh2 made during the citric acid cycle
44:50
all of these reduced electron acceptors they call them because they've picked up electrons all of these reduced electron acceptors are headed to stage 3 oxidative phosphorylation which is the concept I explained in the previous video ok and just to let you know because I think that's a good stopping point for this video and for part 1 just to let you know I want you to I want to show you something all of those nadh made it during stages
45:20
1 glycolysis 1 and 1/2 oxidation of pyruvate and two citric acid cycle all of those nadh that were made in those previous steps are headed here to drop off electrons into the electron transport chain you see nadh drops so NADH drops off at electron transport chain at complex one those electrons move through to complex for where they're picked up by oxygen to form water whereas fadh2 remember there was only one place fadh2 was made a couple of them were made in the citric acid
45:54
cycle and the fadh2 drops off its electrons here and complex two NADH drops off its electrons here at complex one either way those electrons move from left to right they get picked up by oxygen the terminal electron acceptor at the end oxygen is reduced to water okay and that spontaneous reaction those spontaneous process of electrons flowing through these electron transport chains power the chains that's that's the spontaneous process that powered the
46:25
pumps to pump the protons out those protons form a high concentration in the intermembrane space those protons then diffuse back into the matrix from the interment space back into the matrix of the mitochondria through a process known as chemiosmosis imposing a proton motive force providing a proton motive force which causes spinning of ATP synthase and then phosphorylation of ADP and inorganic phosphate right adjoining of ADP adenosine diphosphate with inorganic
46:59
phosphate to form ATP 28 of them right 28 ATP are made this way by oxidative phosphorylation and there you go okay that was what when I explained on the previous video so anyway again why did we make NADH during glycolysis during oxidation of pyruvate during Krebs cycle citric acid cycle why did we make all this NADH so that it could come here and drop off a complex one why did we make the fadh2 from the previous steps actually during citric acid cycle so
47:29
that it could come here and drop off a complex - without the NADH that was made during the previous steps and without the fadh2 that was made during the previous steps this step would not work oxidation oxidative phosphorylation oxidative phosphorylation would not happen right this ATP this 28 ATP that's made by the phosphorylation this ATP would not be made if not for the reduced electron carriers from the previous steps and
47:58
that's why you have the previous steps that's why you have glycolysis that's why you have oxidation oxidation of pyruvate that's why you have citric acid cycle so that you can provide the electrons to these electron carriers so that you can reduce them to nadh and fadh2 and they can come here and drop off those electrons nadh drops off a complex one fadh2 drops off at complex two and that's why in this overview slide remember this nice overview slide
48:27
I showed you earlier let me show you see this overview slide that's why during glycolysis you see you make two nadh and where does where does it go those nadh are on their way to the electron transport chain and the the two nadh made during step one-and-a-half where those NADH off to see the arrows to the electron transport chain during citric acid cycle where are those six nadh and two fa th had it off to the electron transport chain so you could
48:55
power the electron transport chain so the electron transfer chain actually pumps protons right you see nadh drops off here FIDH here that spontaneous movement of electrons pumps protons powers the pumps actively pump protons into the intermembrane space you have a high concentration of protons those protons diffuse back in providing a force that spins the ATP synthase to make ATP by joining the inorganic phosphate with ADP to make ATP via
49:25
oxidative phosphorylation so that's how the big process works you get 28 ATP here to from Krebs cycle to from glycolysis that's 32 but remember you invested two ATP to get the pyruvate into the mitochondria I know this is a long process and its convoluted but it will make sense just try to write it out from beginning to end that's a good stopping point for today tomorrow or the day after I will post part two of two for cellular respiration so please watch
49:54
that okay and let me know if you have any questions I do understand that this is a complicated and complex process but you can't do it and I will have a review video as well for you okay we won't go through this stuff near the end so that's a good stopping point for today we have gone through a majority of this chapters material and I'll finish it off soon all right thanks for watching let me know if you have any questions and I'll see you next time
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