Which of the following is correct regarding electron transport system of respiration ?

Options

A. NADN is directly oxidised bye complex IV.
B. Complex V is a mobile electron carrier.
C. Complex IV cause the reduction molecular oxygen .
D. Complex II contains two copper centres .

Answer

To solve the question regarding the electron transport system (ETS) of respiration, we will analyze each option provided and determine which statement is correct.

### Step-by-Step Solution:

1. **Understanding the Electron Transport System (ETS)**:
- The ETS is a series of protein complexes located in the inner mitochondrial membrane that facilitate the transfer of electrons from electron donors to electron acceptors via redox reactions.

2. **Analyzing Each Option**:
- **Option A**: "NADP is directly oxidized by Complex-4."
- This statement is incorrect. NADP (Nicotinamide adenine dinucleotide phosphate) is not oxidized by Complex-4. Instead, NADH, which is derived from NAD+, is oxidized by Complex-1.

- **Option B**: "Complex-5 is a mobile electron carrier."
- This statement is also incorrect. Complex-5, also known as ATP synthase, is not a mobile electron carrier. It is involved in synthesizing ATP using the proton gradient established by the electron transport chain, not in carrying electrons itself.

- **Option C**: "Complex-4 causes reduction of molecular oxygen."
- This statement is correct. Complex-4, also known as cytochrome c oxidase, is responsible for the reduction of molecular oxygen to water. It accepts electrons from cytochrome c and transfers them to oxygen, which is the final electron acceptor in the chain.

- **Option D**: "Complex-2 contains 2 copper centers."
- This statement is incorrect. Complex-2, also known as succinate dehydrogenase, does not contain copper centers. The copper centers are found in Complex-4.

3. **Conclusion**:
- The correct statement regarding the electron transport system of respiration is **Option C**: "Complex-4 causes reduction of molecular oxygen."