Advanced Placement (AP) Biology Practice Exam

Which molecule can enhance the reaction rate of an enzyme?

1. Inhibitor

2. Coenzyme

3. Substrate

4. Denaturant

The correct answer is: Coenzyme

A coenzyme is an organic molecule that binds to an enzyme and enhances its activity, typically by assisting in the transfer of electrons, atoms, or functional groups during the enzymatic reaction. Coenzymes often serve as carriers for specific molecules, facilitating the conversion of substrates into products. This enhancement of the enzyme's function leads to an increased reaction rate, thereby improving the overall efficiency of metabolic processes. In contrast, inhibitors typically decrease enzyme activity by binding to the enzyme or the enzyme-substrate complex, leading to inhibited reaction rates. Substrates are the reactants that enzymes act upon, which are necessary for the reaction to occur but do not inherently increase the rate by themselves; rather, they are transformed into products. Denaturants disrupt the structural integrity of an enzyme, often leading to loss of function and a decrease in reaction rate. Therefore, coenzymes play a crucial role in enhancing enzyme activity and overall metabolic efficiency.