Question

How many CO2 molecules are released if 2 molecules of glucose are catabolized to acetyl-CoA via the reactions of glycolysis and pyruvate dehydrogenase? a) 4 b) 6 c) 2 d) 1 e) 12

Answer 1

The answer is 4 CO2 molecules.A glucose is a 6 Carbon molecule which converts into 2 moleules of pyruvic acid (which is a 3 carbon molecule) through glycolysis. When 2 glucose molecules undergo glycolysis it produce 4 molecules of pyruvic acid.There is no CO2 evolution in glycolysys.

Pyruvic acid is catabolized to Acetyl CoA by the action of pyruvate dehydrogenase , each molecule of pyruvic acid converted into a molecule od Acetyl CoA (which is a 2 carbon molecule ) by the evolution of a CO2 molecule.

So,there is 4 pyruvic acid molecules, hence the release of 4 CO2 molecules.

1 glucose$\rightarrow$2 pyruvate molecules$\rightarrow$2 Acetyl CoA molecules (release 2 CO2 molecules)

2 glucose$\rightarrow$ 4 pyruvate molecules$\rightarrow$4 Acetyl CoA molecules (release 4 CO2 molecules)