Question 118

(Multiple Choice)

Use the following information to answer the questions below.
In the presence of oxygen,the three-carbon compound pyruvate can be catabolized in the citric acid cycle.First,however,the pyruvate (1)loses a carbon,which is given off as a molecule of CO₂,(2)is oxidized to form a two-carbon compound called acetate,and (3)is bonded to coenzyme A.
-Why is coenzyme A,a sulphur-containing molecule derived from a B vitamin added to acetate?


A)because sulphur is needed for the molecule to enter the mitochondrion
B)in order to utilize this portion of a B vitamin that would otherwise be a waste product from another pathway
C)to provide a relatively unstable molecule whose acetyl portion can be readily transferred to a compound in the citric acid cycle
D)because it drives the reaction that regenerates NAD⁺
E)in order to remove one molecule of CO₂

Answer