In a biological reaction, succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, a substance that resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the amount of succinate molecules to those of malonic acid reduces the inhibitory effect of malonic acid. What is malonic acid's role with respect to succinate dehydrogenase?a. It is a competitive inhibitor.
b. It is an allosteric regulator.
c. It is able to bind to succinate.
d. It blocks the binding of fumarate.

A competitive inhibitor competes with the substrate for the active site of the enzyme. Binding of the competitive inhibitor to the active site of enzyme forms enzyme-inhibitor complex and does not allow the substrate to bind to the enzyme. This inhibits the reaction. However, the competitive inhibition is overcome by increasing the concentration of substrate around the enzyme to facilitate its binding to the enzyme's active site.

According to the given information, malonic acid competes with succinate for the active site of enzyme succinate dehydrogenase and inhibits the reaction. This inhibition is overcome by increasing the succinate concentration around the enzyme. This makes malonic acid a competitive inhibitor to succinate dehydrogenase.