Which one is not a coenzyme ?

Options

A. `NAD^(+)`
B. NADPH
C. FAD
D. ATP.

Answer

To determine which option is not a coenzyme, we can analyze each of the given options based on their definitions and functions.

### Step-by-Step Solution:

1. **Understanding Coenzymes**:
- Coenzymes are non-protein organic molecules that assist enzymes in catalyzing biochemical reactions. They are often derived from vitamins and play crucial roles in metabolic processes.

2. **Analyzing the Options**:
- **NAD+ (Nicotinamide Adenine Dinucleotide)**: This is a well-known coenzyme involved in redox reactions, particularly in the electron transport chain. It is derived from niacin (vitamin B3).
- **NADPH (Nicotinamide Adenine Dinucleotide Phosphate)**: Similar to NAD+, NADPH is also a coenzyme derived from niacin and is involved in anabolic reactions and the electron transport chain.
- **FAD (Flavin Adenine Dinucleotide)**: FAD is another coenzyme that plays a role in various metabolic reactions, including those in the citric acid cycle and is derived from riboflavin (vitamin B2).
- **ATP (Adenosine Triphosphate)**: ATP is primarily known as the energy currency of the cell. While it can act as a substrate or allosteric modulator, it does not assist enzymes in catalyzing reactions in the same way that coenzymes do.

3. **Conclusion**:
- Based on the analysis, **ATP** is not a coenzyme. It serves different roles in cellular metabolism but does not function as a coenzyme.

### Final Answer:
**ATP is not a coenzyme.**