Advanced Placement (AP) Biology Practice Exam

What role do enzymes play in metabolic pathways?

1. They are not involved in metabolic pathways

2. Their role is only to catalyze the final product

3. They assist in altering specific molecules

4. They inhibit metabolic reactions

The correct answer is: They assist in altering specific molecules

Enzymes play a crucial role in metabolic pathways by assisting in altering specific molecules through the process of catalysis. They act as catalysts that speed up chemical reactions without being consumed in the process. Each enzyme is specific to a particular substrate, leading to the conversion of that substrate into products through a series of steps in a metabolic pathway. By lowering the activation energy required for reactions, enzymes enable the metabolic processes to occur more efficiently and at a faster rate under physiological conditions. This specificity is fundamental because metabolic pathways involve numerous steps, each with distinct reactions and enzymes. Enzymes ensure that these reactions happen in a regulated manner, allowing for the orderly flow of metabolites through the pathway. This regulation is essential for maintaining homeostasis within the cell and responding to varying metabolic demands. In contrast to this correct response, metabolic pathways do require enzymes to function properly, and they do not just catalyze the final product nor do they inhibit reactions, but rather facilitate the transformation of various substrates through multiple intermediates. Hence, the correct assertion aligns with the essential role enzymes play in enabling and regulating metabolism.