In muscles and nerves, cytoplasmic NADH yields

Options

A. 3 ATP
B. 2 ATP
C. 1 ATP
D. No ATP

Answer

To solve the question regarding the yield of ATP from cytoplasmic NADH in muscles and nerves, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Cytoplasmic NADH**:
- Cytoplasmic NADH is produced during glycolysis when glucose is broken down in the cytoplasm. For every molecule of glucose, two molecules of NADH are generated.

2. **Transport of NADH**:
- NADH produced in the cytoplasm cannot directly enter the mitochondria due to the impermeability of the inner mitochondrial membrane. Therefore, it must use specific mechanisms to transfer its electrons to the electron transport chain.

3. **Mechanisms of NADH Utilization**:
- There are two main mechanisms by which cytoplasmic NADH can be utilized:
- **Malate-Aspartate Shuttle**: This is the more efficient mechanism found in liver, heart, and kidney cells, which allows for the production of 3 ATP per NADH.
- **Glycerol-Phosphate Shuttle**: This less efficient mechanism is found in brain and skeletal muscle cells, which results in the production of only 2 ATP per NADH.

4. **Conclusion for Muscles and Nerves**:
- In muscles and nerve cells, the cytoplasmic NADH utilizes the glycerol-phosphate shuttle, yielding only 2 ATP per molecule of NADH.

5. **Final Answer**:
- Therefore, in muscles and nerves, cytoplasmic NADH yields **2 ATP**.