Which one of the following statements about enzymes is true ?
1. Enzymes are proteins whose shape does not help in their functions.
2. Enzymes lower the reaction rate by lowering the activation energy
3. Enzymes do not show a high specificity during biological reactions.
4. Enzyme activity is affected by the change in temperature and pH

Options

A. Only 2
B. Only 1
C. Only 3
D. Only 4

Answer

To determine which statement about enzymes is true, we will analyze each option step by step.

### Step 1: Analyze Statement 1
**Statement:** Enzymes are proteins whose shape does not help in their functions.
**Analysis:** This statement is incorrect. Enzymes are indeed proteins, and their specific three-dimensional shape is crucial for their function. The shape of an enzyme determines its active site, where substrate molecules bind, facilitating the chemical reaction.

**Hint:** Remember that the structure of proteins, including enzymes, is closely linked to their function.

### Step 2: Analyze Statement 2
**Statement:** Enzymes lower the reaction rate by lowering the activation energy.
**Analysis:** This statement is also incorrect. Enzymes actually increase the reaction rate by lowering the activation energy required for the reaction to occur. This allows reactions to proceed more quickly than they would without the enzyme.

**Hint:** Consider how enzymes interact with substrates and the energy required for reactions.

### Step 3: Analyze Statement 3
**Statement:** Enzymes do not show a high specificity during biological reactions.
**Analysis:** This statement is incorrect. Enzymes are highly specific for their substrates. Each enzyme typically catalyzes only one type of reaction or acts on a specific substrate, which is essential for the regulation of metabolic pathways.

**Hint:** Think about the lock-and-key model of enzyme-substrate interaction.

### Step 4: Analyze Statement 4
**Statement:** Enzyme activity is affected by the change in temperature and pH.
**Analysis:** This statement is correct. Enzymes have optimal temperature and pH ranges in which they function best. Deviations from these conditions can lead to decreased enzyme activity or denaturation, affecting the overall rate of the reaction.

**Hint:** Recall how temperature and pH can influence the structure and function of proteins.

### Conclusion
After analyzing all four statements, we find that the only true statement about enzymes is:

**Correct Answer:** Enzyme activity is affected by the change in temperature and pH (Statement 4).