Question

The complete oxidation of pyruvate by the stepwise removal of :
a) All the hydrogen atoms, leaving two molecules of carbon dioxide
b) All the hydrogen atoms, leaving three molecules of carbon dioxide
c) Two hydrogen atoms, leaving three molecules of carbon dioxide
d) None of the above

Answer 1

Hint: As we know pyruvate is one of the important molecules which is found at the intersection of the various biochemical pathways. It is considered to be one of the end products of glycolysis which is being transported to the mitochondria in the participation of the citric acid cycle.

Complete answer:
Pyruvate is the end product of glycolysis, which is transported to mitochondria and further oxidised in aerobic respiration for complete oxidation to carbon dioxide and water. It is considered to be an aerobic process as it requires oxygen.
Steps involved in aerobic respiration are as follows;
a. Pyruvic acid enters into the mitochondria.
b. Complete oxidation of pyruvate occurs by the stepwise removal of all the hydrogen atoms thereby
leaving three molecules of $CO_2$.
c. The passing on the electrons removed as part of the hydrogen atoms to molecular oxygen with simultaneous synthesis of ATP.

Therefore the correct answer is option C which states that “The complete oxidation of pyruvate by the stepwise removal of two hydrogen atoms, leaving three molecules of carbon dioxide” takes place.

Note:
Pyruvate is oxidized to acetyl-Coenzyme A and carbon dioxide by the pyruvate dehydrogenase complex enzyme which is in short known as PDC. The PDC contains multiple copies of three enzymes and is located in the mitochondria of eukaryotic cells and also in the cytosol of prokaryotes. In the conversion of pyruvate to acetyl-CoA, one molecule of nicotinamide adenine dinucleotide hydrogen and one molecule of carbon dioxide is formed.