[Music] hi everyone this is andy from med school eu and in today's lecture we're going to continue talking about bioenergetics and now that we know how to produce our organic compound through the process of photosynthesis in organisms that are considered to be photoautotrophs we're now going to see how the organic compound is going to be broken down in order to produce energy and this process will be called cellular respiration and the first step of cellular respiration is glycolysis so first of all before we begin looking at the steps of glycolysis we must do our cellular respiration overview just to see what the process is like where it occurs and what is the general reactions that happen in this process so we first going to begin with just the overall redox reaction of cellular respiration to see what is oxidized and what is reduced because this is the opposite reaction of photosynthesis because in photosynthesis we begin with water and carbon dioxide remember we fixate carbon dioxide and we produce organic compound and release oxygen into the atmosphere consumers that are going to consume the energy made by photoautotrophs they're going to consume this glucose molecule or any other organic compound that is found and they're going to use oxygen in order to perform this reaction and to get lots and lots of atp produced along with our water and co2 that will be released into the atmosphere for the photoautotrophs to pick up and do their cycle so this all happens in the cycle and the series of reactions and first we must highlight that the glucose molecule right here is going to be oxidized so that's oxidation reaction and of course the oxygen into the water is going to be reduced so we must also know that cellular respiration occurs in three different phases and the first one glycolysis we're going to talk about in detail in today's video however following that there's going to be the process of pyruvate oxidation and the citric acid cycle and the final stage will be oxidative phosphorylation that occurs on the mitochondrial inner membrane so that's the electron transport that is going to produce lots and lots of atp for us so let's label our primary cellular respiration organelle and that's going to be the mitochondria so we must recognize the mitochondria has two membranes that's got this outer membrane and we have the inner membrane and a lot of the reactions will happen within these membranes we also got the mitochondrial matrix so it's called matrix here so what happens is glycolysis occurs in the cytosol so it occurs outside the mitochondrion and it occurs on in in the cytoplasm of a cell and what happens is the products of glycolysis are going to enter the matrix of the mitochondria by going through the fusion of the outer membrane and then it's going to use a transporter to get through the inner membrane and it's going to go right into the matrix and in the matrix the second part will happen called pyruvate oxidation as well as the citric acid cycle so the products of pyruvate oxidation will be the the reactants for the citric acid cycle and this all occurs in the matrix of the mitochondrion now once the products of the citric acid cycle have formed and we get a lot of our nadh and fadh2 which are going to be classified as electron carriers these are going to be hydrolyzed by oxidative phosphorylation on the mitochondrial inner membrane right here on the mitochondrial inner membrane and this whole process is going to be called oxidative phosphorylation in other words it is the etcs electron transport chain and through that we're going to produce lots and lots of atp molecules so now we're going to take a look at glycolysis and see the steps all the steps that are involved in glycolysis and how they're catalyzed and it's important to note that glycolysis there are 10 steps and all 10 steps are catalyzed by enzymes so enzymes are involved in all of these 10 steps in order for the glycolysis to go through and produce our products as we're going to see next so there are 10 steps however those 10 steps are divided into two different phases and the first phase is called the energy requiring phase because we need energy in order for this phase to go through so what we have is one glucose molecule which has six carbons and we're going to produce through five reactions so this this has five reactions that's the first five reactions their energy requiring because overall you're going to produce two molecules of glyceraldehyde three phosphate in other words there's two molecules of g3p which have three carbons and in order to do that we need to hydrolyze two atp molecules we need energy in order for this process to happen so we we undergo the hydrolysis of atp the phosphate will be added onto the molecules and we produce our g3p molecule now looking at step number two what we have is another five reactions and these these reactions are going to be energy releasing reactions and what this really means is that we're actually going to produce atp we're going to produce energy and it's exergonic and the energy requiring stage is endergonic it requires energy to get to the products here this happens spontaneously because it is exergonic and what we have is five reactions where the two molecules of g3p undergo oxidation where the they are going to lose electrons and protons in order to make two nadh molecules so as you can see here the four electrons and four protons are going to be taken away from the two g3p molecules and they're going to produce two nadh now at the same time the atp is under is is going to undergo phosphorylation where the phosphate will be taken away from the g3p molecules and is going to produce four atp and finally the g3p is going to become oxidized into two pyruvate molecules and two water molecules and pyruvate has three carbons so looking at the summary here we've got the one glucose molecule that that is our organic compound that's going to become two pyruvate molecules and two water however during this reaction we also have our 4 atp released right here and 2 atp consumed and therefore we get a net plus of 2 atp and we also get a net plus of two nadh molecules and these are going to be very important for the production of atp further down into the cellular respiration cycle so now we're going to take a look at all of these reactions step by step and see exactly which enzymes are involved and what kind of reactions are involved to understand why we get our products so we're going to take a look at the first five reactions which are energy requiring and the first reaction is going to be glucose molecule are six carbons and they're gonna undergo phosphorylation reaction in order to produce glucose six phosphate so what this really means is that the hexokinase so kinases are actually the catalytical enzymes that undergo phosphorylation reactions they contribute the catalysis of phosphorylation reactions and here we use atp as our substrate for the phosphate and the phosphate will be added on to the molecule of glucose producing glucose 6-phosphate so we just added a phosphate molecule to the sixth carbon of glucose so just remember just keep in mind that kinases are the enzymes that catalyze phosphorylation reactions now looking at the next step we take our glucose 6-phosphate and it's going to be isomerized into fructose 6-phosphate so this fructose is an isomer of glucose and therefore it's it's under gonna undergo isomerization reaction through the enzyme called phosphogluco mutase so don't worry about the phosphogluco you should worry about the mutase you must know that mutase typically catalyzes isomerization reactions now looking at the next step we take our fructose 6-phosphate and it's going to be transformed into fructose 1 6-bis phosphate so what this really means is we added another phosphate molecule and that means we used a kinase enzyme kinase enzymes again they catalyze the reactions of phosphorylation so here again we use an atp molecule in order to phosphorylate our fructose 6-phosphate and add another phosphate to the molecule here and now looking at the fourth step of the reaction what we actually have is is we we have we take our fructose 1 6 bis phos phosphate and it's it's gonna undergo a split reaction so it's going to split into a g3p and dihydroxyacetone phosphate so what this really is it's a hydrolysis reaction so it's high draw lysis reaction and typically this reaction is going to be catalyzed by an enzyme called aldolase that's going to split the fructose 1 6 bisphosphate into g3p molecule and this dihydroxyacetone phosphate and we're going to see what happens to this dihydroxyacetone phosphate in the next step however you should recognize that we we have our g3p molecule and from the previous slide we know that we got to produce two molecules of g3p at the end of the five steps so looking at the next step the final step of the energy requiring phase is that we're going to use an isomerase enzyme in order to transform our dihydroxyacetone phosphate into a g3p molecule so as you can see now we have we have made our two g3p molecules and we have hydrolyzed we have taken two atp molecules one two right here so this is what we're left with at the end of the first part energy requiring phase of glycolysis so now that we have made our two molecules of g3p we're going to take a look at glycolysis steps 6 to 10 which are energy producing steps and here's what we got so in step 6 we take our g3p so here again just to point out right away is that all of these reactions will be happening twice because we have two molecules of g3p in the previous first five steps we only had the one glucose molecule so they only happen once now here in the last five steps we're gonna have these reactions occur two times so what we got is our g3p molecule and it's on it's going to undergo the first redox reaction of glycolysis and what we have is the enzyme dehydrogenase is going to catalyze this redux reaction so what we have is g3p is going to be oxidized into one three bisphosphoglycerate and nad plus is going to be reduced into nadh and a proton will be released as well and we're also going to add on an inorganic phosphate to our molecule now in the second step we take our 1 3 bis phosphoglycerate and it's going to produce three phosphoglycerate so we're going to remove a phosphate molecule and here what's going to happen is something called substrate level phosphorylation so this is one way one of the primary ways atp is made in cellular respiration by the process called substrate level i'm going to write it down sub straight level phosphorylation for relation and substrate level phosphorylation simply means that atp is produced by the means of of a substrate so what we have is our 1 3 bisphosphoglycerate the kinase remember is going to add a phosphate onto the atp it's going to catalyze this reaction and the phosphate is going to be removed from our organic compound and it's going to be left off with just the 3-phosphoglycerate now looking at the next step the 3-phosphoglycerate is going to undergo a mutase reaction which is shifting of a chemical group to another within the same molecule so again we have our phosphate at carbon 3 on the glycerate and is going to be shifted over to carbon 2 of the glycerate and pretty much nothing else happens that's what mutases are known for is they're known for isomerization reactions and these mutase reactions which simply means shifting of a chemical group or a functional group now next we have our two phosphoglycerate that is going to undergo another redox reaction where water is going to be produced and a pap molecule and pap stands for phosphoenol pyruvate and this is going to be catalyzed by the enzyme called enolase and enolase is going to produce water as a side product of the reaction and finally in step number 10 we're going to have another substrate level phosphorylation so whenever atp is produced that is not on the electron transport chain on not on the etc we call it substrate level phosphorylation so here we have another substrate level phosphorylation and the for of course is going to be catalyzed by a kinase enzyme where the pep molecule is going to be converted into pyruvate where the the phosphate is going to be lost to atp and this is why we produce an atp molecule right here and finally we produce our pyruvate which is the final product of glycolysis with three carbons being the backbone of the molecule and remember these reactions occur two times so they happen twice for each g3p therefore we produce two pyruvate molecules per glucose molecule so this concludes our video on glycolysis which is the first part of cellular respiration and in the next video we're going to take a look at the next two steps of cellular respiration which will involve the pyruvate oxidation plus the citric acid cycle and finally we're going to take a look at oxidative phosphorylation [Music] you