Small protein attached to outer surface of inner mitochondrial membrane which acts as mobile carrier for transfer of electrons between complex III and IV is :

Options

A. Cyt. a
B. Cyt. b
C. Cyt. c
D. Cyt. d

Answer

To solve the question regarding the small protein attached to the outer surface of the inner mitochondrial membrane that acts as a mobile carrier for the transfer of electrons between complex III and IV, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: The question is about the electron transport chain (ETC) in mitochondria, which is crucial for cellular respiration. The ETC consists of several complexes that facilitate the transfer of electrons.

2. **Identify the Components**: In the electron transport chain, there are several complexes (Complex I, II, III, and IV) and mobile carriers. The mobile carriers include coenzymes and proteins that transport electrons between these complexes.

3. **Focus on the Specifics**: The question specifies a small protein that is attached to the outer surface of the inner mitochondrial membrane and is responsible for transferring electrons between complex III and complex IV.

4. **Recall the Function of Cytochrome c**: Cytochrome c is a small heme protein that is located on the outer surface of the inner mitochondrial membrane. It plays a critical role in the electron transport chain by transferring electrons from complex III (cytochrome bc1 complex) to complex IV (cytochrome c oxidase).

5. **Conclude the Answer**: Given the information about the role and location of cytochrome c, we can conclude that the small protein that acts as a mobile carrier for the transfer of electrons between complex III and IV is **cytochrome c**.

### Final Answer:
The small protein attached to the outer surface of the inner mitochondrial membrane that acts as a mobile carrier for the transfer of electrons between complex III and IV is **cytochrome c**.

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