1. Electron transport chain produces 32 ATP molecules.
During the transport of two electrons from NADH to O2, it is now estimated that
10 protons will be accumulated in the intermembrane space, while from
ubiquinone (QH2) there will be only 6.
ATP synthase requires three H + for the synthesis of ATP, so that the maximum possible P / O ratios are about 3 or 2.
However, the transport of metabolites in the mitochondrial matrix and the exchange of ATP4- against ADP3- in the intermembrane space also use protons.
- Therefore, the P / O ratios for the oxidation of NADH and QH2 are rather of the order of 2.5 or 1.5 depending on the case.
- If we evaluate the energy balance of aerobic glycolysis, we obtain a yield of 32 ATP per glucose
2. Glycolysis Creates four ATP molecules, but then gains overall only two.
The glycolysis uses one mole of glucose to produce:
* 2 moles of pyruvate
* 2 moles of reduced coenzymes (NADH)
* 4 moles of ATP (knowing that 2 moles of ATP were consumed during glycolysis).
* 2 moles of water
* 2 moles of protons (H +)
So that 2 moles of ATP are produced by treating 1 mole of glucose.
3. Citric acid cycle Gives off carbon dioxide
The Krebs cycle is composed of 10 steps catalyzed by eight different enzymes. During the cycle are produced, from a mole of acetate and up to the stage CO2 and H2O:
* 2 moles of CO2
* 3 moles of NADH + H +
* 1 mole of CoQ10H2
* 1 mole of GTP
So for one mole of glucose (which produces 2 moles of acetate) the balance will be twice that.
4. Electron transport chain Gives off water
The eukaryotic respiratory chain has been extensively studied. It consists essentially of four protein complexes counted from I to IV. Electrons with a high transfer potential of NADH enter NADH dehydrogenase, or complex I, to give NAD +, while those of succinate enter at the succinate dehydrogenase, or complex II, to give fumarate. A third entry point exists at the ETF dehydrogenase level for electrons of electron-transferring flavoproteins (ETFs). Coenzyme Q-cytochrome c reductase, or complex III, then transfers electrons from Q10H2 to cytochrome c in the intermembrane space, and cytochrome c oxidase, or complex IV, transfers the electrons of four reduced cytochromes c to a molecule of O2 oxygen to form two H2O water molecules.
5. Citric acid cycle Produces two ATP molecules.
It is found that the Krebs cycle produces only one ATP equivalent (a GTP) for an acetyl CoA molecule. Remember that for one mole of glucose, the balance is double.
Most of the potential chemical energy is produced as a reducing power (NADH + H + and CoQ10H2). This reducing power is subsequently used in the mitochondrial respiratory chain to produce 11 other ATP molecules via a proton gradient and an ATP synthase that is sometimes erroneously attributed to the Krebs cycle.
