Which is electron carrier common to both photosynthesis and respiration?

Options

A. cytochrome
B. phytochrome
C. phaeophytin
D. plastocynin

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks for an electron carrier that is common to both photosynthesis and respiration.

2. **Identifying the Options:**
The options provided are:
- Cytochrome
- Phytochrome
- Pheophytin
- Plastocyanin

3. **Analyzing Each Option:**
- **Cytochrome:**
- Cytochromes are redox-active proteins that contain heme (an iron-containing compound). They are involved in the electron transport chain in both respiration and photosynthesis.
- **Phytochrome:**
- Phytochromes are photoreceptors in plants that detect light but are not involved in electron transport.
- **Pheophytin:**
- Pheophytin is a chemical compound that acts as the first electron acceptor in photosystem II, primarily in purple bacteria, and is not common to respiration.
- **Plastocyanin:**
- Plastocyanin is involved in the electron transport chain in photosynthesis but is not a common carrier in respiration.

4. **Conclusion:**
Based on the analysis, the only electron carrier that is common to both photosynthesis and respiration is **Cytochrome**.

5. **Final Answer:**
The electron carrier common to both photosynthesis and respiration is **Cytochrome**.

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