FREE Biochemistry Enzymes and Metabolism Questions and Answers
Which of the following statements about enzymes is TRUE?
Enzymes lower the activation energy, allowing reactions to proceed faster. They are not consumed (option A is false), activity is pH and temperature-dependent (option C is false), and not all enzymes need cofactors (option D is false).
In glycolysis, which enzyme catalyzes the conversion of glucose to glucose-6-phosphate?
Hexokinase catalyzes the first step of glycolysis, phosphorylating glucose to glucose-6-phosphate using ATP. Phosphofructokinase acts later in glycolysis, and aldolase is involved in splitting fructose-1,6-bisphosphate.
Which of the following is a key regulatory enzyme in the citric acid cycle?
Isocitrate dehydrogenase is a rate-limiting enzyme in the citric acid cycle, regulated by ATP, ADP, and NADH levels. Citrate synthase and succinate dehydrogenase are important but less tightly regulated.
During oxidative phosphorylation, the final electron acceptor in the electron transport chain is:
Oxygen acts as the final electron acceptor, forming water as a by-product. NAD⁺ and FAD are electron carriers, and water is a product, not the acceptor.
Which of the following statements about competitive inhibition is TRUE?
Competitive inhibitors compete with the substrate for binding at the enzyme's active site. They do not affect Vmax but increase the apparent Km. Increasing substrate concentration can overcome inhibition (option C is false), and they usually form reversible, non-covalent bonds.
