Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds would you expect to initially decrease in concentration?A) Citrate
B) Fumarate
C) Isocitrate
D) Pyruvate
E) Succinate

B) is the correct option

Explanation:

Succinate dehydrogenase is the smallest component of electron transport chain and consists of four different subunits including FAD, 3 Fe-S centers It catalyzes oxidation of succinate to fumarate and electrons released transferred to ubiquinoneSuccinate dehydogenase transfer electrons from succinate to ubiquinone via FADH2 thus this complex directly links tricarboxylic acid cycle to electron transport chainActivity of succinate dehydrogenase is inhibited by malonate which is a competitive inhibitor as a result oxidation of succinate to fumarate will not occur and hence concentration of fumarate will decrease