Cytochrome c is a small protein attached to the

Options

A. outer surface of the outer mitochondrial membrane and acts as a mobile carrier for transfer of electrons between complex II and III
B. inner surface of the outer mitochondrial membrane and acts as a mobile carrier for transfer of electrons between complex III and IV
C. outer surface of the inner mitochondrial membrane and acts as a mobile carrier for transfer of electrons between complex III and IV
D. inner surface of the inner mitochondrial membrane and acts as a mobile carriar for transfer of electrons between complex III and IV

Answer

To solve the question regarding cytochrome c, we will analyze the options provided and determine the correct answer based on our understanding of its function and location within the mitochondria.

### Step-by-Step Solution:

1. **Understanding Cytochrome c**:
- Cytochrome c is a small protein that plays a crucial role in the electron transport chain (ETC) within mitochondria. It is involved in the transfer of electrons between different complexes of the ETC.

2. **Identifying the Location**:
- Cytochrome c is located in the inner mitochondrial membrane. It is not bound to the membrane but is loosely associated with its outer surface.

3. **Analyzing the Options**:
- **Option 1**: "Outer surface of outer mitochondrial membrane and acts as a mobile carrier for transfer of electrons between complexes 2 and 3."
- This is incorrect because cytochrome c is not located on the outer mitochondrial membrane.

- **Option 2**: "Inner surface of the outer mitochondrial membrane and acts as a mobile carrier of transfer of electrons between complex 3 and 4."
- This is also incorrect because cytochrome c is not on the inner surface of the outer mitochondrial membrane.

- **Option 3**: "Outer surface of inner mitochondrial membrane and acts as a mobile carrier for transfer of electrons between complex III and IV."
- This is correct. Cytochrome c is indeed found on the outer surface of the inner mitochondrial membrane and transfers electrons between complex III and complex IV.

- **Option 4**: "Inner surface of mitochondrial membrane and acts as a mobile carrier for transfer of electrons between complex III and IV."
- This is incorrect as it does not specify the correct surface of the inner mitochondrial membrane where cytochrome c is located.

4. **Conclusion**:
- The correct answer is **Option 3**: "Outer surface of inner mitochondrial membrane and acts as a mobile carrier for transfer of electrons between complex III and IV."