Final answer:
The measure of affinity for enzyme-catalyzed reactions that follow sigmoid kinetics is Km, which is the Michaelis constant. Km is a measure of how quickly the enzyme becomes saturated with a particular substrate. An enzyme with a smaller Km has a higher affinity for the substrate.
Step-by-step explanation:
The measure of affinity for enzyme-catalyzed reactions that follow sigmoid kinetics is Km, which is the Michaelis constant. Km is a measure of how quickly the enzyme becomes saturated with a particular substrate. It is related to the concentration of substrate ([S]) at which the reaction rate reaches half of its maximum value (Vmax).
An enzyme with a smaller Km has a higher affinity for the substrate, meaning it can reach its maximum reaction rate at a lower substrate concentration. Conversely, an enzyme with a larger Km has a lower affinity for the substrate, requiring a higher substrate concentration for the reaction to proceed at its maximum rate.