Which reaction is affected to a much lesser extent by temperature?

Options

A. Light reaction
B. Dark reaction
C. Both (1) and (2)
D. none of these

Answer

### Step-by-Step Solution:

1. **Understanding the Reactions**:
- Photosynthesis consists of two main reactions: the light reaction and the dark reaction (Calvin cycle).
- The light reaction occurs in the presence of sunlight and produces ATP and NADPH.
- The dark reaction (Calvin cycle) utilizes ATP and NADPH to fix carbon dioxide (CO2).

2. **Nature of the Reactions**:
- The light reaction is a photochemical process, meaning it directly involves light energy.
- The dark reaction is a biochemical process, which involves enzymatic reactions that are sensitive to temperature changes.

3. **Temperature Sensitivity**:
- Enzymatic reactions, such as those in the dark reaction, are highly sensitive to temperature. Changes in temperature can significantly affect the activity of enzymes like Rubisco and PEP carboxylase.
- In contrast, the light reaction, while it can be affected by extreme temperatures, is generally more stable until a critical temperature threshold is reached.

4. **Conclusion**:
- Since the dark reaction is more dependent on enzymes that are affected by temperature, it is more sensitive to temperature changes.
- Therefore, the light reaction is affected to a much lesser extent by temperature changes.

5. **Final Answer**:
- The reaction that is affected to a much lesser extent by temperature is the **light reaction**.