The free energy for the oxidation of glucose to carbon dioxide and water is appr

Question

The free energy for the oxidation of glucose to carbon dioxide and water is approximately -700 kilocalories per mole and the free energy for the reduction of NAD+ to NADH is +50 kilocalories per mole. Why are only two molecules of NADH formed during glycolysis when it appears that more than a dozen could be formed?

A. Most of the free energy available from the oxidation of glucose is used to produce ATP in glycolysis.

B. Glycolysis is a very inefficient reaction, with much of the energy of glucose released as heat.

C. Most of the free energy available from the oxidation of glucose remains in pyruvate.

D. There is no CO2 or water produced as products of glycolysis.

E. Glycolysis consists of many enzymatic reactions, each of which extracts some energy from glucose

Explanation / Answer

C. Most of the free energy available from the oxidation of glucose remains in pyruvate.

Glycolysis is an anaerobic process, through which one glucose molecules is breakdown into two molecules of three carbon pyruvate. The glycolysis of each glucose molecule generates 2 ATP molecules.

Glucose + 2 NAD+ + 2 Pi + 2 ADP 2 pyruvate + 2 NADH + 2 ATP + 2 H+ + 2 H2O + heat.

The pyruvate is a high energy molecule, which are converted into acetyl-CoA and enter into the citric acid cycle.

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