Yield of ATP from oxidation of glucose

The yield of ATP from oxidation of glucose depends on the stoichiometry of the respiratory chain with respect to ATP synthesis, which is still somewhat controversial.

         A             B              C
glucose -> 2 pyruvate -> 2 acetylCoA -> Kreb's cycle

A generates 					2 ATP 	2 NADH (cytoplasmic)
B generates 2 x 1NADH = 				2 NADH
C generates 2 x (1 ATP, 1 FADH, 3 NADH) = 	2 ATP	6 NADH  2 FADH2

	Total					4 ATP	10 NADH 2 FADH2

For the mitochondria, "textbook" stoichiometries are:

ATP/2e ratio for NADH oxidation = 2.5
ATP/2e ratio for succinate oxidation (via FADH2) = 1.5

These are based on the following assumptions for H+/ATP and H+/2e ratios:

Complex I span	             4H+/2e
Complex II span	             0H+/2e
Complex III span	     2H+/2e ( + 2 scalar H+/2e)
Complex IV span	             4H+/2e (  - 2 scalar H+/2e)

ATP-synthase                 3H+/ATP
Transport of phosphate, 
and exchange of ADP/ATP-     1H+/ATP
  Total for ATP synthesis    4H+/ATP

From this:

NADH -> O2  		10 H+/2e  10/4 = 	2.5 ATP/NADH
Succinate -> O2	6 H+/2e		  6/4 = 	1.5 ATP/FADH2

The main areas of uncertainty are the stoichiometry for the Complex I span, and the H+/ATP stoichiometry, which may not be integer. However, the textbook values are likely to be pretty close to the real values, and within the range of experimental uncertainty.

The yield of ATP from the cytoplasmic NADH depends on the pathway by which the reducing equivalents reach the respiratory chain, which is tissue dependent. If via the glutamate/aspartate shuttle, the yield is the same as the mitochondrial yield, minus 1 H+/NADH (or 0.25 ATP/NADH); if via dihydroxyacetone phosphate, the Complex I span is by-passed, losing 1 ATP/NADH.


©Copyright 2001, Antony Crofts, University of Illinois at Urbana-Champaign, a-crofts@uiuc.edu