30
30
in Living Systems
24
24
18
18
Relative rate of enzyme action
12
12
0
10 20 30 40 50 60 70 80 90 100
Temperature (°C)

Which hypothesis most likely explains the results at 60°C?

A. There was not enough molecular movement for the enzyme to be effective at this temperature.
B. The enzyme is effective only at very high temperatures.
C. The enzyme changed shape because of the high temperature.



Answer :

To determine which hypothesis most likely explains the results at 60°C, let's carefully analyze the situation involving enzyme activity and temperature.

1. Understanding enzyme activity and temperature:
- Enzymes are biological catalysts that speed up chemical reactions in living organisms. They have an optimal temperature range where they function most efficiently.
- At temperatures lower than the optimal, the rate of enzyme activity decreases because molecules are moving more slowly, leading to fewer collisions between enzymes and substrates.
- At temperatures higher than the optimal, enzymes may denature, meaning they lose their specific 3D structure and can no longer bind to substrates effectively.

2. Analyzing the enzyme activity data:
- At the given temperatures (10°C, 20°C, 30°C, 40°C, 50°C, 60°C), the enzyme activity increases up to a certain point (likely around 30-40°C) and then starts to decrease. By the time we reach 60°C, the enzyme activity has significantly dropped, indicating a change in enzyme efficiency.

3. Examining the hypotheses:
- Hypothesis A: "There was not enough molecular movement for the enzyme to be effective at this temperature."
- At 60°C, molecular movement is quite rapid, so this hypothesis is unlikely because the temperature is already quite high and should promote molecular movement.
- Hypothesis B: "The enzyme is effective only at very high temperatures."
- If the enzyme were only effective at very high temperatures, we would expect it to work better as the temperature increases. However, the data shows a decrease in enzyme activity at 60°C, which contradicts this hypothesis.
- Hypothesis C: "The enzyme changed shape because of the high temperature."
- Enzymes are sensitive to temperature, and high temperatures can cause them to denature (change shape). A significant drop in enzyme activity at 60°C supports this hypothesis, as the enzyme likely lost its proper shape and function.

4. Conclusion:
- Based on the data and the nature of enzyme activity, the most likely explanation for the results at 60°C is that the enzyme denatured due to the high temperature. Denaturation leads to a loss of the enzyme's functional shape, which in turn decreases its activity.

Therefore, the correct hypothesis that most likely explains the results at 60°C is:

C. The enzyme changed shape because of the high temperature.