_____ is the 5C DCA molecules of citric acid cycle.

Options

A. Succinic acid
B. Oxalosuccinic acid
C. alpha'-ketoglutaric acid
D. Fumaric acid

Answer

To solve the question regarding the 5C DCA molecules of the citric acid cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Citric Acid Cycle**: The citric acid cycle, also known as the Krebs cycle, is a key metabolic pathway that involves several biochemical reactions to produce energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

2. **Identify the 5-Carbon Molecules**: In the citric acid cycle, we need to identify the 5-carbon (5C) molecule. The cycle includes several intermediates, and we are looking for the one that has five carbon atoms.

3. **Recall the Key Intermediates**: The main intermediates in the citric acid cycle include citrate (6C), isocitrate (6C), alpha-ketoglutarate (5C), succinate (4C), fumarate (4C), and malate (4C).

4. **Focus on the 5C Molecule**: Among these intermediates, alpha-ketoglutarate is the only molecule that contains five carbon atoms. It is also known as DCA (Dicarboxylic Acid).

5. **Confirm the Answer**: Since alpha-ketoglutarate is the 5C DCA molecule in the citric acid cycle, we conclude that the answer to the question is alpha-ketoglutaric acid.

### Final Answer:
**Alpha-ketoglutaric acid** is the 5C DCA molecule of the citric acid cycle.