After which of the following treatments (I - III) would an enzyme still be expected to have activity?
I. Protease treatment.
II. Heating almost to the point of denaturation.
III. Freezing and then thawing once only.

Options

A. I only
B. III only
C. I and II only
D. II and III only

Answer

To determine after which treatments an enzyme would still be expected to have activity, we will analyze each treatment step by step.

### Step 1: Analyze Treatment I - Protease Treatment
- **Explanation**: Proteases are enzymes that break down proteins into smaller peptides or amino acids. When an enzyme is treated with proteases, it is likely to be degraded or denatured, leading to a loss of its functional activity.
- **Conclusion**: After protease treatment, the enzyme is expected to lose its activity.

**Hint**: Consider how proteases interact with proteins and their effects on enzyme structure.

### Step 2: Analyze Treatment II - Heating Almost to the Point of Denaturation
- **Explanation**: Heating an enzyme can lead to denaturation, where the enzyme's structure is altered, affecting its active site and overall functionality. However, if the heating is not sufficient to fully denature the enzyme, it may still retain some activity.
- **Conclusion**: If the enzyme is heated only to the point just before complete denaturation, it may still exhibit some activity.

**Hint**: Think about the temperature range that causes denaturation and how enzymes might retain activity if not fully denatured.

### Step 3: Analyze Treatment III - Freezing and Then Thawing Once Only
- **Explanation**: Freezing can cause changes in the enzyme's structure due to ice crystal formation, which may lead to denaturation. Thawing may not reverse these changes, and the enzyme could become inactive.
- **Conclusion**: After freezing and thawing, the enzyme is likely to lose its activity.

**Hint**: Reflect on how temperature changes affect the stability of proteins and enzymes.

### Final Conclusion
Based on the analysis:
- Treatment I (Protease treatment) leads to loss of activity.
- Treatment II (Heating almost to the point of denaturation) may retain some activity.
- Treatment III (Freezing and thawing) leads to loss of activity.

Thus, the enzyme would still be expected to have activity after treatments II only.

**Correct Answer**: Treatment II only.