Final answer:
The correct answer is option b. Enzyme B has a higher affinity for its substrate compared with enzyme A, as indicated by its lower Km value.
Step-by-step explanation:
The question concerns the enzyme-substrate affinity as indicated by the Michaelis constant (Km). The Km value represents the substrate concentration at which the reaction velocity is half of the maximum velocity (Vmax). It is inversely related to the affinity between an enzyme and its substrate. A lower Km implies a higher affinity, as the enzyme can reach half of its maximum velocity at a lower substrate concentration. Conversely, a higher Km suggests a lower affinity, requiring a higher substrate concentration to achieve half of the Vmax.
Regarding enzymes A and B, with Km values of 10 micromolar and 0.1 micromolar respectively, it can be concluded that enzyme B has a higher substrate affinity than enzyme A. Because enzyme B can achieve half of its Vmax at a significantly lower substrate concentration, it binds more readily to its substrate compared to enzyme A. Therefore, the correct answer to the student's question is: b. Enzyme B has a higher affinity for its substrate compared with enzyme A.