During light reaction in a chloroplasts , the highest number of protons are found in

Options

A. Stroma
B. Lumen of thylakoids
C. Inter membrane space
D. Antennae complex

Answer

To solve the question about where the highest number of protons are found during the light reaction in chloroplasts, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Light Reactions**:
- The light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts. These reactions convert light energy into chemical energy in the form of ATP and NADPH.

**Hint**: Remember that light reactions are dependent on light and occur in specific structures within the chloroplast.

2. **Identify Key Structures**:
- In chloroplasts, the thylakoids are sac-like structures where the light reactions take place. The space inside these thylakoids is called the lumen.

**Hint**: Focus on the structure of chloroplasts and the specific areas where reactions occur.

3. **Proton Movement**:
- During the light reactions, protons (H⁺ ions) are pumped into the lumen of the thylakoids as electrons move through the electron transport chain. This creates a proton gradient.

**Hint**: Think about how protons are generated and where they accumulate during the light reactions.

4. **Comparison of Regions**:
- The main regions to consider are:
- **Stroma**: The fluid matrix surrounding the thylakoids.
- **Lumen of Thylakoids**: The interior space of the thylakoids where protons accumulate.
- **Intermembrane Space**: The space between the inner and outer membranes of the chloroplast.
- **Antennae Complex**: Part of the photosystem that captures light energy but does not store protons.

**Hint**: Compare the functions and characteristics of each region to determine where protons are most concentrated.

5. **Conclusion**:
- The highest concentration of protons during the light reactions is found in the **lumen of the thylakoids**. This is due to the pumping of protons into this space during the electron transport process.

**Final Answer**: The correct answer is **Lumen of Thylakoid** (option no. 2).