What do the terms '[S]', 'Vmax', and 'km' represent in the Michaelis-Menten equation?

In the context of the Michaelis-Menten equation, '[S]', 'Vmax', and 'km' each hold specific meanings that are crucial for understanding enzyme kinetics.

'[S]' represents the concentration of the substrate involved in the enzymatic reaction. It reflects how much of the substrate is available for the enzyme to convert into products. The concentration of substrate is a key variable since it directly influences the rate of the reaction.

'Vmax' stands for the maximum velocity of the reaction when the enzyme is saturated with substrate. At this point, all active sites of the enzyme molecules are occupied, and the reaction rate reaches its peak. This value is important because it reflects the overall efficiency of the enzyme when substrate availability is not a limiting factor.

'km', or the Michaelis constant, is a measure of the substrate concentration at which the reaction velocity is half of Vmax. It provides insight into the affinity of the enzyme for its substrate; a lower km value indicates a higher affinity, meaning that the enzyme can reach half of its maximal activity at a lower substrate concentration.

Together, these parameters help to characterize the nature and effectiveness of enzyme-catalyzed reactions, making option B the correct representation of what they signify within the Michaelis-M