Oxidative phosphorylation and photophosphorylation both require the electron carrier

Options

A. Cytochrome
B. Oxygen
C. Carbon dioxide
D. Water

Explanation

To solve the question "Oxidative phosphorylation and photophosphorylation both require the electron carrier," we will analyze the processes involved and identify the correct electron carrier from the given options.

### Step-by-Step Solution:

1. **Understanding Oxidative Phosphorylation**:
- Oxidative phosphorylation occurs in the mitochondria during cellular respiration.
- It involves the electron transport chain (ETC), where electrons are transferred through a series of proteins, ultimately leading to ATP production.
- The primary electron carriers involved in this process are NADH and FADH2, which donate electrons to the ETC.

2. **Understanding Photophosphorylation**:
- Photophosphorylation occurs in chloroplasts during photosynthesis.
- It uses light energy to generate ATP and involves the electron transport chain as well.
- In this process, the primary electron carriers are plastoquinone and ferredoxin, which transport electrons derived from water splitting and light absorption.

3. **Identifying the Electron Carrier**:
- Both processes require specific electron carriers to facilitate the transfer of electrons.
- The question asks for a common electron carrier that is involved in both oxidative phosphorylation and photophosphorylation.

4. **Evaluating the Options**:
- **Cytochrome**: This is a type of protein that acts as an electron carrier in both the electron transport chain of mitochondria (oxidative phosphorylation) and in the thylakoid membrane of chloroplasts (photophosphorylation).
- **Oxygen**: While oxygen is the final electron acceptor in oxidative phosphorylation, it is not an electron carrier.
- **Carbon Dioxide**: This is a substrate in photosynthesis but not an electron carrier.
- **Water**: Water is a source of electrons in photophosphorylation but not an electron carrier itself.

5. **Conclusion**:
- The correct answer is **Cytochrome**, as it is the electron carrier required in both oxidative phosphorylation and photophosphorylation.

### Final Answer:
The electron carrier required for both oxidative phosphorylation and photophosphorylation is **Cytochrome**.

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