Coenzyme `NAD^(+)" and FAD` are connected with respiratory reactions as they

Options

A. Are involved in each step of ATP synthesis
B. Function in Krebs cycle and terminal oxidative phosphorylation
C. Act as hydrogen carrier
D. Are reducing agents.

Answer

**Step-by-Step Solution:**

1. **Understanding Coenzymes**: Coenzymes are organic molecules that assist enzymes in catalyzing reactions. In cellular respiration, NAD⁺ (Nicotinamide adenine dinucleotide) and FAD (Flavin adenine dinucleotide) play crucial roles.

2. **Role of NAD⁺ and FAD**: Both NAD⁺ and FAD are involved in redox reactions. They accept electrons and protons during metabolic processes, which is essential for energy production.

3. **NAD⁺ in Respiration**: During glycolysis and the Krebs cycle, NAD⁺ is reduced to NADH. This conversion is vital as NADH carries high-energy electrons to the electron transport chain, where ATP is synthesized.

4. **FAD in Respiration**: Similarly, FAD is reduced to FADH₂ during the Krebs cycle. Like NADH, FADH₂ also transports electrons to the electron transport chain, contributing to ATP production.

5. **Conclusion**: The primary function of NAD⁺ and FAD in respiration is to act as hydrogen carriers. They facilitate the transfer of electrons and protons, which is crucial for the redox reactions that lead to ATP synthesis.

6. **Final Answer**: Therefore, the correct answer is that NAD⁺ and FAD are connected with respiratory reactions as they act as hydrogen carriers.

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