At how many places in Krebs cycle , FADH2 is / are formed ?

Options

A. 1
B. 2
C. 3
D. 4

Answer

To determine how many times FADH2 is formed in the Krebs cycle, we can follow these steps:

### Step 1: Understand the Krebs Cycle
The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

### Step 2: Identify the Key Reactions
In the Krebs cycle, several key reactions occur, and during these reactions, different electron carriers are produced, including NADH and FADH2.

### Step 3: Focus on FADH2 Production
FADH2 is specifically produced during the oxidation of succinate to fumarate. This reaction is catalyzed by the enzyme succinate dehydrogenase. In this process, succinate donates two hydrogen atoms to FAD, reducing it to FADH2.

### Step 4: Count the Occurrences of FADH2 Formation
In the entire Krebs cycle, FADH2 is produced only once during the conversion of succinate to fumarate. Therefore, there is only one place in the Krebs cycle where FADH2 is formed.

### Conclusion
Thus, the answer to the question is that FADH2 is formed at **one place** in the Krebs cycle.

### Final Answer
The correct option is **1**.

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