The oxidation of a molecule of `"FADH"_(2)` yield less ATP (2ATP) and a moleule of `"NADH"_(2)` yields 3ATP but `"FADH"_(2)` yields only 2 ATP because

Options

A. Carries few electrons
B. Pssses its electrons to a transport molecule later in the chain and at a lower level
C. Has a lower energy conformation than `NADH_(2)`
D. Is formed in the cytosol and energy is lost when it shuttles its electron across the mitochondrial membrane

Answer

To understand why the oxidation of a molecule of FADH₂ yields less ATP (2 ATP) compared to NADH (which yields 3 ATP), we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Electron Transport Chain (ETC)**:
- The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane. It is responsible for transferring electrons from electron carriers (NADH and FADH₂) to oxygen, ultimately producing ATP through oxidative phosphorylation.

2. **Role of NADH and FADH₂**:
- NADH and FADH₂ are both electron carriers that donate electrons to the ETC. However, they enter the chain at different points.
- NADH donates electrons to Complex I (NADH dehydrogenase), while FADH₂ donates electrons to Complex II (succinate dehydrogenase).

3. **ATP Yield from NADH**:
- When NADH donates electrons to Complex I, it initiates a series of reactions that pump protons (H⁺ ions) across the inner mitochondrial membrane into the intermembrane space. This creates a proton gradient.
- The proton gradient is then used by ATP synthase to produce ATP. The oxidation of one NADH can lead to the production of approximately 3 ATP molecules due to the proton pumping through three complexes (I, III, and IV).

4. **ATP Yield from FADH₂**:
- FADH₂, on the other hand, enters the ETC at Complex II. This complex does not contribute to the proton gradient as effectively as Complex I does.
- As a result, when FADH₂ donates its electrons, it only leads to the pumping of protons through Complex III and Complex IV, but not through Complex I. This results in a lower ATP yield of about 2 ATP per FADH₂.

5. **Conclusion**:
- The difference in ATP yield between NADH and FADH₂ is primarily due to their entry points in the electron transport chain and the number of protons pumped across the membrane. NADH contributes to more proton pumping than FADH₂, leading to the production of more ATP.

### Final Answer:
FADH₂ yields only 2 ATP because it enters the electron transport chain at Complex II, which does not pump protons as effectively as Complex I (where NADH enters), resulting in less ATP production.

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