Glycolysis ATP Yields

In the preparatory phase of glycolysis, ATP is invested to convert glucose to fructose 1,6-bisphosphate. The bond between C-3 and C-4 is then broken to yield two molecules of triose phosphate. 

Two ATPs are used in glycolysis and four ATPs are synthesized for each molecule of glucose so that the net yield is two ATPs per glucose. Under aerobic conditions, the two NADH molecules arising from glycolysis also yield energy via oxidative phosphorylation. 

This compares with only two ATPs as the net ATP yield from glycolysis. Thus an extra four ATPs per glucose are required to reverse glycolysis. 

But even if a combination of pathways usually is used, the ATP yield can nevertheless be elevated two- to fourfold any animal anaerobes utilizing such fermentations therefore automatically reduce by a factor of two to four their anaerobic needs for glucose. Although impressive, this factor is still a long way from the order-of-magni-tude difference between anaerobic glycolysis and oxidative glucose metabolism. 

The net yield of ATP in anaerobic glycolysis (ATP/ glucose) in the presence of arsenate (ASO42-) instead of phosphate is ... 

The answer is b. (Murray, pp 123-148. Scriver, pp 2367-2424. Sack, pp 159-175. Wilson, pp 287-317.) Aerobic glycolysis can be defined as the oxidative conversion of glucose to two molecules of pyruvate. In the process, two molecules of ATP and two molecules of NADH are produced. Since reducing equivalents from the two molecules of NADH produced in the cytoplasm must be transported into the mitochondrion for oxidation, it is not known how many ATP molecules are produced. On the assumption that two ATP molecules are formed per molecule of NADH oxidized via the glycerol phosphate shuttle, the ATP yield in aerobic glycolysis can be calculated as six ATP molecules per mole of glucose utilized. 

Describe how the electrons produced by glycolysis are delivered to the electron transport chain. What role do amino acids play in this process What would be the consequence for overall ATP yield per glucose molecule if a mutation inactivated this delivery system What would be the longer-term consequence for the activity of the glycolytic pathway ... 

Reflect and Apply What should be the net ATP yield for glycolysis when fructose, mannose, and galactose are used as the starting compounds Justify your answer. 

These answers are readily obtained if one remembers the ATP yields from the various parts of glycolysis and remembers that (1) cytoplasmic NADH yields only 1.5 ATP,... 

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