Inner mitochondrial membrane is not permeable to

Options

A. NADH
B. Pyruvate
C. Acetate
D. `alpha`-ketoglutarate.

Answer

**Step-by-Step Solution:**

1. **Understanding Mitochondrial Structure:**
- Mitochondria have two membranes: the outer mitochondrial membrane and the inner mitochondrial membrane. The space between these membranes is called the intermembrane space, while the area inside the inner membrane is known as the mitochondrial matrix.

2. **Identifying the Processes:**
- The Krebs cycle occurs in the mitochondrial matrix, while the electron transport chain takes place in the inner mitochondrial membrane. Glycolysis occurs in the cytosol, where glucose is converted to pyruvate, producing NADH in the process.

3. **Analyzing the Options:**
- The question asks which substance is not permeable to the inner mitochondrial membrane. The options are:
- NADH
- Pyruvate
- Acetate
- Alpha-ketoglutarate

4. **Determining Permeability:**
- NADH is not permeable to the inner mitochondrial membrane. It cannot cross this membrane directly.
- Pyruvate, acetate, and alpha-ketoglutarate are permeable to the inner mitochondrial membrane. Pyruvate crosses via mitochondrial pyruvate carrier proteins (MPC1 and MPC2), while acetate can diffuse across the membrane.

5. **Conclusion:**
- Since NADH cannot cross the inner mitochondrial membrane directly, the correct answer is that the inner mitochondrial membrane is not permeable to NADH.

**Final Answer:**
The inner mitochondrial membrane is not permeable to NADH.

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