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. (b) Graph and explain the relationship between the reaction rate and the substrate concentration. How and why did the results of the two experiments differ?.

Verified step by step guidance

1. Step 1: Plot the data from Table A on a graph with enzyme concentration on the x-axis and reaction rate on the y-axis.
2. Step 2: Plot the data from Table B on a separate graph with lactose concentration on the x-axis and reaction rate on the y-axis.
3. Step 3: Analyze the graph from Table A to observe the relationship between enzyme concentration and reaction rate. Note how the reaction rate increases as enzyme concentration increases.
4. Step 4: Analyze the graph from Table B to observe the relationship between lactose concentration and reaction rate. Note how the reaction rate increases with lactose concentration up to a certain point and then levels off.
5. Step 5: Compare the results of the two experiments. Explain that in Table A, the reaction rate increases with enzyme concentration because more enzyme molecules are available to catalyze the reaction. In Table B, the reaction rate increases with lactose concentration until the enzyme becomes saturated, after which the rate levels off because the enzyme is working at its maximum capacity.

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 and enzyme concentration, affect the speed of the reaction. The Michaelis-Menten model is often used to describe the relationship between substrate concentration and reaction rate, highlighting the concept of saturation where increasing substrate concentration no longer increases the reaction 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 reaction rate typically increases until a maximum rate is reached, known as Vmax. This relationship is crucial for understanding how enzymes function under different conditions, as seen in the experiments where varying lactose concentrations affected galactose production.

Enzyme Concentration

Enzyme concentration is the amount of enzyme present in a reaction mixture. Higher enzyme concentrations generally lead to increased reaction rates, provided there is sufficient substrate available. In the experiments, varying enzyme concentrations in Table A showed a direct correlation with the rate of galactose production, illustrating how enzyme availability can limit or enhance reaction rates depending on substrate levels.