Aerobic Glucose Metabolism

Summary of ATP synthesis from Oxidative Phosphorylation

How efficient is ATP synthesis. It was previously indicated that theoretically each pair of electrons transferred from NADH to O₂ COULD provide suffiecient free energy to synthesize up to 7 ATP.... but that was also hedged by indicating that it would likley be far fewer.

In the simple case, there are three complexes that are involved in transporting H⁺ across the inner mitochondria membrane. In actuality each complex pumps enough H⁺ to synthesize one ATP for every pair of electron transferred.

Recalling the summary from page 4 of this module.....
Now we can convert each of those NADH to ~3 ATP and each reduced flavin to 2 ATP (remember that the the reduced flavin is from succinate dehydrogenase .... which IS complex II .... and that complex II does not pump H⁺ like complex I, III and IV and the others.

Pathway	ATP	NADH	reduced flavin

Glycolysis totals	2 ATP	2 NADH	none

Pyruvate Dehydrogenase	none	2 NADH	none

Kreb's cycle totals	2 ATP (as GTP)	6 NADH	2 reduced flavin

OVERALL totals	4 ATP	10 NADH	2 reduced flavin

CONVERT to ATP TOTALS	4 ATP	30 ATP	4 ATP

This data ignores some energy lost on tranporting NADH into the mitochondria... but that is fine by me

Where as we obtained 2 ATP per glucose from the non-oxidative metabolism here including oxidative phosphorylation our total yield can be up to 38...... almost 20 times more energy yielded for the same glucose molecule through the anaerobic processes. All due to our use of O₂ as a terminal electron acceptor.

Efficiency

The number of 3 ATP per pair of electrons (~1 for each complex) is experimentally determined. We find that about 38 ATP are synthesize for each glucose. IF the conversion of energy from electron transfer to ATP synthesis were 100% efficient, THEN the number of ATP could be closer to ~80 or so. So it turns out that we are about 40-50% efficient in capturing the energy release from glucose oxidation in ATP.