Question

Indicate whether an enzyme is saturated or not saturated in each of the following conditions: a. Adding more substrate does not increase the rate of reaction. b. Doubling the substrate concentration doubles the rate of reaction.

Short answer

a) Saturated, b) Not saturated

Step-by-step solution

Title - Understanding Saturation

An enzyme is considered saturated when all of its active sites are occupied by substrate molecules. This usually occurs at high substrate concentrations.

Title - Analyzing Condition (a)

Condition (a) states that adding more substrate does not increase the rate of reaction. This implies that the enzyme is already working at maximum capacity, meaning it is saturated.

Title - Analyzing Condition (b)

Condition (b) states that doubling the substrate concentration doubles the rate of reaction. This indicates that the enzyme is not saturated because the reaction rate can still be increased by adding more substrate.

Key concepts

enzyme active sites

Enzymes are proteins that help speed up biochemical reactions. They have specific regions called active sites where substrate molecules bind. The shape of the active site is complementary to the shape of the substrate, much like a lock and key.

When a substrate binds to an enzyme's active site, a temporary enzyme-substrate complex is formed. This interaction lowers the activation energy needed for the reaction to occur, making it proceed faster.

Each enzyme has a finite number of active sites. When an enzyme's active sites are all occupied by substrates, we say that the enzyme is 'saturated.' At this point, the addition of more substrate will not increase the reaction rate.

substrate concentration

Substrate concentration is a measure of how much substrate is present in a solution. The relationship between substrate concentration and reaction rate is crucial for understanding enzyme kinetics.

At low substrate concentrations, few enzyme molecules are bound to substrate. As you increase substrate concentration, more enzyme active sites become occupied, and the reaction rate increases. However, there is a limit.

Once all active sites on the enzymes are occupied by substrate molecules, any further increase in substrate concentration won't increase the reaction rate. This is because the enzymes are already working at their maximum capacity, and the reaction has reached a plateau.

reaction rate

The reaction rate is the speed at which a chemical reaction takes place. For enzyme-catalyzed reactions, the reaction rate is influenced by several factors like enzyme concentration, temperature, pH, and importantly, substrate concentration.

Initially, as substrate concentration increases, the reaction rate also increases because more active sites on the enzyme molecules are being utilized. However, once all these active sites are occupied, the reaction rate levels off, indicating enzyme saturation.

In condition (a) from our exercise, the addition of more substrate does not increase the reaction rate, suggesting enzyme saturation. In contrast, condition (b) shows that doubling substrate concentration doubles the reaction rate, indicating that the enzyme is not saturated and more active sites are available for binding.