A biologist performed two series of experiments on lactase, the enzyme that hydrolyzes lactose to glucose and galactose. First, she made up 10% lactose solutions containing different concentrations of enzyme and measured the rate at which galactose was produced (grams of galactose per minute). Results of these experiments are shown in Table A below. In the second series of experiments (Table B), she prepared 2% enzyme solutions containing different concentrations of lactose and again measured the rate of galactose production.
Graph and explain the relationship between the reaction rate and the substrate concentration. How and why did the results of the two experiments differ?.
<IMAGE>

Verified step by step guidance

1. Step 1: Analyze Table A to understand the relationship between enzyme concentration and reaction rate. Notice that as the enzyme concentration increases (while keeping lactose concentration constant at 10%), the reaction rate also increases. This indicates that the availability of enzyme directly impacts the rate of galactose production.
2. Step 2: Analyze Table B to understand the relationship between substrate (lactose) concentration and reaction rate. Observe that as lactose concentration increases, the reaction rate initially increases but eventually plateaus. This suggests that the enzyme becomes saturated with substrate at higher lactose concentrations, limiting the reaction rate.
3. Step 3: Graph the data from Table A and Table B. For Table A, plot enzyme concentration on the x-axis and reaction rate on the y-axis. For Table B, plot lactose concentration on the x-axis and reaction rate on the y-axis. Ensure the graphs clearly show the trends observed in the tables.
4. Step 4: Explain the differences in the results of the two experiments. In Table A, the reaction rate increases linearly with enzyme concentration because more enzyme molecules are available to catalyze the reaction. In Table B, the reaction rate plateaus at higher lactose concentrations because the enzyme active sites are fully occupied, demonstrating the concept of enzyme saturation.
5. Step 5: Relate the findings to enzyme kinetics. The results from Table B align with the Michaelis-Menten model, where the reaction rate increases with substrate concentration until the enzyme becomes saturated. The plateau in reaction rate indicates that the maximum velocity (Vmax) of the enzyme has been reached.

Key Concepts

Enzyme Kinetics

Enzyme kinetics is the study of the rates of enzyme-catalyzed reactions. It involves understanding how various factors, such as substrate concentration, enzyme concentration, and temperature, affect the speed of these reactions. The Michaelis-Menten model is a key framework in this area, describing how reaction rates increase with substrate concentration until a maximum velocity (Vmax) is reached, beyond which additional substrate does not increase the rate.

Substrate Concentration

Substrate concentration refers to the amount of substrate available for an enzyme to act upon. In enzyme-catalyzed reactions, as substrate concentration increases, the rate of reaction typically increases until it reaches a saturation point. This is because more substrate molecules lead to more frequent collisions with enzyme active sites, enhancing the reaction rate until all active sites are occupied.

Competitive Inhibition

Competitive inhibition occurs when a molecule similar to the substrate competes for binding to the active site of the enzyme. This can affect the rate of reaction by reducing the number of available active sites for the substrate, leading to a decrease in the overall reaction rate. Understanding competitive inhibition is crucial for interpreting differences in experimental results, as varying concentrations of substrate or enzyme can influence the extent of inhibition.