David Keilin is associated with

Options

A. NAD
B. FAD
C. CoQ
D. Cytochromes

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks about the association of David Keilin.

2. **Analyze the Options**: The options provided are:
- Option 1: NAD
- Option 2: FAD
- Option 3: Coenzyme Q
- Option 4: Cytochrome

3. **Evaluate Each Option**:
- **Option 1 (NAD)**: This option is incorrect. NAD (Nicotinamide adenine dinucleotide) was discovered by Charles Brenner.
- **Option 2 (FAD)**: This option is also incorrect. FAD (Flavin adenine dinucleotide) is a cofactor for various enzymes, but it was not discovered by David Keilin.
- **Option 3 (Coenzyme Q)**: This option is incorrect as well. Coenzyme Q (also known as ubiquinone) was discovered by Karl Falker.
- **Option 4 (Cytochrome)**: This is the correct option. David Keilin is known for rediscovering cytochrome and elucidating its role in cellular respiration in 1925.

4. **Conclusion**: Based on the evaluation, the correct answer is **Option 4: Cytochrome**.

---