01 January 1970 2 10K Report

According to some of newer sources the ATP yield during aerobic respiration is not 36–38, but only about 30–32 ATP molecules / 1 molecule of glucose , because:

ATP : NADH+H+ and ATP : FADH2 ratios during the oxidative phosphorylation appear to be not 3 and 2, but 2.5 and 1.5 respectively. Unlike in the substrate-level phosphorylation, the stoichiometry here is difficult to establish.

ATP synthase produces 1 ATP / 3 H+. However the exchange of matrix ATP for cytosolic ADP and Pi (antiport with OH− or symport with H+) mediated by ATP–ADP translocase and phosphate carrier consumes 1 H+ / 1 ATP as a result of regeneration of the transmembrane potential changed during this transfer, so the net ratio is 1 ATP : 4 H+.

The mitochondrial electron transport chain proton pump transfers acrosstheinnermembrane10H+ /1NADH+H+ (4+2+4)or6H+ /1FADH2 (2+4).

So the final stoichiometry is 1 NADH+H+ : 10 H+ : 10/4 ATP = 1 NADH+H+ : 2.5 ATP 1 FADH2 : 6 H+ : 6/4 ATP = 1 FADH2 : 1.5 ATP

ATP : NADH+H+ coming from glycolysis ratio during the oxidative phosphorylation is

1.5, as for FADH2, if hydrogen atoms (2H++2e−) are transferred from cytosolic NADH+H+ to mitochondrial FAD by the glycerol phosphate shuttle located in the inner mitochondrial membrane.

2.5 in case of malate-aspartate shuttle transferring hydrogen atoms from cytosolic NADH+H+ to mitochondrial NAD+

So finally we have, per molecule of glucose

Substrate-level phosphorylation: 2 ATP from glycolysis + 2 ATP (directly GTP) from Krebs cycle Oxidative phosphorylation

2 NADH+H+ from glycolysis: 2 × 1.5 ATP (if glycerol phosphate shuttle transfers hydrogen atoms) or 2 × 2.5 ATP (malate-aspartate shuttle)

2 NADH+H+ from the oxidative decarboxylation of pyruvate and 6 from Krebs cycle: 8 × 2.5 ATP 2 FADH2 from the Krebs cycle: 2 × 1.5 ATP

Altogether this gives 4 + 3 (or 5) + 20 + 3 = 30 (or 32) ATP per molecule of glucose

The total ATP yield in ethanol or lactic acid fermentation is only 2 molecules coming from glycolysis, because pyruvate is not transferred to the mitochondrion and finally oxidized to the carbon dioxide (CO2), but reduced to ethanol or lactic acid in the cytoplasm.

References:

  • Principles of Biochemistry- Lehninger, Nelson & Cox
  • Biochemistry - Voet & Voet
  • Biochemistry - Zubey & Zubey
  • Biochemistry - Strayer
  • Plant Physiology - Taiz & Zaiger
  • Cellular Respiration - Wikipedia (Updating the concept).
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