First oxidative decarboxylation in aerobic respiration occurs during the conversion of

Options

A. Oxalosuccinic acid to iso citric acid
B. Pyruvic acid to acetyl CoA
C. `alpha`-ketoglutaric acid to succinyl CoA
D. Fumaric acid to malic acid

Answer

To solve the question about where the first oxidative decarboxylation in aerobic respiration occurs, we can follow these steps:

### Step 1: Understand the Process of Aerobic Respiration
Aerobic respiration is a metabolic process that converts glucose into energy in the presence of oxygen. It involves several stages, including glycolysis, the Krebs cycle, and the electron transport chain.

**Hint:** Remember that aerobic respiration starts with glycolysis, which occurs in the cytoplasm.

### Step 2: Identify the Role of Glycolysis
During glycolysis, a six-carbon glucose molecule is broken down into two three-carbon molecules of pyruvic acid. This is the first step of aerobic respiration.

**Hint:** Glycolysis produces pyruvic acid, which is crucial for the next steps in aerobic respiration.

### Step 3: Recognize the Transition to the Krebs Cycle
Before pyruvic acid can enter the Krebs cycle (also known as the citric acid cycle), it must be converted into a two-carbon molecule. This conversion involves decarboxylation (removal of a carbon atom) and is known as oxidative decarboxylation.

**Hint:** The conversion of pyruvic acid to acetyl CoA is essential for its entry into the Krebs cycle.

### Step 4: Identify the Key Reaction
The conversion of pyruvic acid to acetyl CoA occurs in the mitochondrial matrix. During this reaction, one carbon is released as carbon dioxide (CO2), and NAD+ is reduced to NADH. This step is the first oxidative decarboxylation in aerobic respiration.

**Hint:** Look for the reaction that involves the transformation of pyruvic acid into a two-carbon compound.

### Step 5: Conclusion
Based on the above steps, the first oxidative decarboxylation in aerobic respiration occurs during the conversion of pyruvic acid to acetyl CoA.

**Final Answer:** The correct answer is **pyruvic acid to acetyl CoA**.

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