Both respiration and photosynthesis require

Options

A. sunlight
B. green cells
C. cytochromes
D. organic substrate

Answer

**Step-by-Step Solution:**

1. **Understanding the Processes:**
- Photosynthesis and respiration are two fundamental biological processes. Photosynthesis occurs in plants, where they convert light energy into chemical energy (glucose) using carbon dioxide and water. Respiration, on the other hand, is the process by which organisms convert glucose into usable energy (ATP), consuming oxygen and releasing carbon dioxide.

2. **Identifying Common Requirements:**
- Both processes involve electron transfer chains. In respiration, this occurs in the mitochondria, while in photosynthesis, it occurs in the thylakoid membranes of chloroplasts.

3. **Key Components:**
- In respiration, cytochromes play a crucial role in the electron transport chain, facilitating the transfer of electrons and aiding in ATP production. Similarly, cytochromes are also involved in the photosynthetic electron transport chain.

4. **Conclusion:**
- The commonality between respiration and photosynthesis is that both processes require cytochromes for electron transfer and ATP production. While photosynthesis requires sunlight and green cells (chlorophyll), respiration does not require sunlight.

**Final Answer:**
Both respiration and photosynthesis require cytochromes for the electron transport chain involved in ATP production.

---