Final answer:
The enzyme is said to be saturated when the reaction rate reaches a plateau at maximum velocity despite increases in substrate concentration. This saturation point corresponds to the maximum velocity (Vmax) at which all active sites of enzyme molecules are occupied by substrate.
Step-by-step explanation:
When the relationship between substrate concentration and reaction rate reaches a plateau of maximum velocity, the enzyme is said to be saturated.
The phenomenon where increasing substrate concentration no longer speeds up the reaction rate occurs when all enzyme active sites are occupied by substrate molecules. This state is known as enzyme saturation, and the reaction rate at this point is at its maximum, termed as Vmax. The given amount of enzyme can handle no more substrate, and any additional substrate present does not affect the rate at which the product is formed.
Furthermore, the Michaelis-Menten constant, Km, is the substrate concentration at which the reaction rate is half of Vmax, and it's a measure of how efficiently an enzyme can bind substrate and convert it to product. The enzyme's activity at this stage is limited by the rate at which the enzyme-substrate complexes convert to product; thus, higher substrate concentrations do not increase the velocity of the reaction beyond this point.