so we know it that when glucose is broken down anaerobic cell respiration we produce ATP molecule so some number are produced in glycolysis and then we generate the remaining ATP molecules in a citric acid cycle and on the electron transport chain but the question is what is the number of ATP molecules that we actually generate when a single glucose is broken down in aerobic cell respiration so this is what I'd like to discuss in this lecture and let's begin with glycolysis so glycolysis takes place entirely in the cytoplasm of the cell and so let's suppose this is a cytoplasm and this is the mitochondrion now a single glucose is broken down into two pyruvate molecules and glycolysis and in a process we also generate two ATP molecules and we produce two NADH molecules now the ATP molecules can be used directly by the cell to power some type of biological process in that cell but to produce ATP molecules from NADH that NADH must move on to the electron transfer chain found on the inner membrane of the mitochondrion so we have the outer membrane the inner membrane we have electron transport chain and this is the matrix of the mitochondria and this is the inter membrane space now the question is how many ATP molecules do we actually form when a single NADH is transported onto the electron transport chain from the cytoplasm well the answer to that question basically depends on the type of shuttle that the cell actually uses some cells such as skeletal muscle cells use a shuttle known as the glycerol 3-phosphate shuttle and in this particular case the high-energy electrons are transported onto complex three of the electron transport chain and so what that means is we bypass complex one and in this particular case 1.5 ATP molecules will be formed when a single NADH produced in glycolysis moves on to the electron transport chain so that means because we form two NADH molecules to multiply by one point five is 3 and so 3 ATP molecules will be formed per 2 NADH molecules produced in glycolysis in cells that utilize the g3p shuttle to actually move the NADH onto the electron transport chain so where do we get that number well when the two electrons from NADH are ultimately transported onto complex 3 we know that complex 3 of the electron transport chain actually moves a net amount of 2 H+ ions and so actually we're moving them from the matrix into the intermembrane space so it's in this direction and then when the electrons are moved onto this particular complex complex 4 we move a net quantity of 4 h+ and so we basically create a proton gradient where we move 6 h+ ions and so when these six h+ ions will move from the instrument brain space back into the matrix this ATP synthase complex 5 will use them to actually generate the ATP molecules and remember we need four H+ ion so four h+ ions have to move from complex 5 to actually generate a single ATP molecule and what that means is when the 6 plus h ions move through ATP synthase we need four of them to actually generate a single ATP molecule and so 6 divided by 4 gives us 1.5 ATP molecules are generated when the 6 H+ ions move when a single NADH is oxidized by the electron trans poor chain now what about the other shuttle so cells such as cardiac muscle cells so the heart cells and liver cells utilize a slightly different shuttle known as malate aspartate shuttle and the thing about this shuttle is the high-energy electrons produced by or found on the NADH produced in the glycolytic pathway ultimately end up being transported onto complex one and complex one essentially pumps on that amount of 484 H+ ions into the intermembrane space and so here we have four plus two plus four that gives us a total of 10 and so 10 divided by 4 gives us 2.5 and so what that means is the NADH molecules produced in glycolysis in cells that utilize the malate aspartate shuttle basically generate a net amount of 2.5 ATP molecules per single NADH that is oxidized by the electron transport chain and so in cells that utilize Mally aspartate shuttle we produce 2 multiplied by 2 point 5 so 5 ATP molecules so this is the number of ATP that we produced in glycolysis so the 2 ATP molecules are produced directly and then we also form the ATP via the oxidative phosphorylation that takes place on the electron transport chain and this ranges anywhere from 3 to 5 ATP depending on a type of shuttle that the cell actually uses now the 2 pyruvate molecules produced in the cytoplasm then move into the matrix of the mitochondria and in the matrix we have pyruvate decarboxylation that transforms the 2 pyruvate into two acetyl coenzyme a molecules and in the process we also generate the two NADH molecules and the two NADH molecules because they're produced directly in the matrix of the mitochondria they move directly onto complex one and so a signal NADH oxidized by the electron transport chain and the matrix goes through all these complexes and so we pump out these ten H+ ions and that means a single NADH oxidized by the electron transport chain produced in pyruvate decarboxylation produces 2.5 ATP molecules and because we have two of these two multiplied by 2.5 gives us five ATP molecules produced from this process now the majority of the NADH are produced in the citric acid cycle so we have a net result of two gtp 6 nadh and to fadh2 molecules that are produced when two of these acetyl coenzyme a molecules are fed into the citric acid cycle now the two gtp are basically catalyzed by special enzyme into two ATP molecules and so those are the two ATP molecules shown here now the six NADH because they're produced directly in the matrix of the mitochondria each one of these NADH is produces 2.5 ATP molecules and 6 x 2.5 gives us 15 now recall that when a single fadh2 is oxidized as oxidized by the electron transport chain it is oxidized by complex 2 and so we bypass complex 1 and that means when a single fadh2 is oxidized by complex to complex - doesn't actually pump any protons and so those electrons extracted from fadh2 ultimately end up being transported onto complex 3 so we bypass complex one and so six protons six protons total are pumped and so 6 divided by 4 gives us one point five and so one point five ATP molecules are produced per single fadh2 that is oxidized by the electron transport chain and so because we have 2 of them 2 multiplied by 1 point 5 gives us 3 so to summarize we have anywhere from 2 plus three five two two plus five seven ATP molecules produced from glycolysis that includes the two ATP and the NADH is that are basically oxidized by the electron transport chain we have a net amount of five ATP produced by pyruvate carboxylase in when the NADH s are oxidized by electron transport chain and the total for the citric acid cycle so we have two three and fifteen that's 20 so 20 plus five that's 25 so we have two and three so 25 plus five die gives us 30 or in the case of the Mallee aspartate shuttle we have 32 so a net result of 32 32 ATP molecules are formed from one glucose molecule that is metabolized broken down in a robic cell respiration