Which one of the following statement is not correct.

Options

A. The energy released during the electron transport system is utilised in ATP synthesis
B. ATP synthase is complex IV in ETS
C. NADH dehydrogenase is complex I in ETS
D. Ubiquinone receives reducing equivalents via `FADH_(2)` (Complex II)

Answer

To determine which statement is not correct regarding the Electron Transport System (ETS) and ATP synthesis, let's analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding the Electron Transport System (ETS)**:
- The Electron Transport System is a series of complexes located in the inner mitochondrial membrane that facilitate the transfer of electrons from electron donors like NADH and FADH2 to electron acceptors such as oxygen.
- This process generates a proton gradient that is used to synthesize ATP.

2. **Analyzing the First Statement**:
- "The energy released during the electron transport system is utilized in ATP synthesis."
- This statement is correct. The energy released during electron transport is indeed used to drive ATP synthesis through oxidative phosphorylation.

3. **Analyzing the Second Statement**:
- "ATP synthesis is a complex in complex 4 of ETS."
- This statement is incorrect. ATP synthesis occurs at ATP synthase, which is often referred to as complex V, not complex IV. Complex IV is involved in the transfer of electrons to oxygen.

4. **Analyzing the Third Statement**:
- "NADH dehydrogenase is complex 1."
- This statement is correct. NADH dehydrogenase is indeed the first complex in the electron transport chain.

5. **Analyzing the Fourth Statement**:
- "Ubiquinone receives reducing equivalents via FADH2 from complex 2."
- This statement is also correct. Ubiquinone (coenzyme Q) receives electrons from FADH2, which is processed by complex II.

### Conclusion:
The statement that is not correct is:
- **"ATP synthesis is a complex in complex 4 of ETS."**