Consider the first reaction of TCA cycle.
Acetyl `CoA + OA A +H_(2)O overset("Citrate")underset("synthase")rarr A + CoA` What is true about compound A?

Options

A. First product of TCA cycle
B. Tricarboxylic acid and six carbon compound
C. It undergoes reorganisation in the presence of enzyme aconitase to form cis-aconitate
D. All of these

Explanation

To solve the question regarding compound A in the first reaction of the TCA cycle, we need to analyze the reaction step by step.

### Step-by-Step Solution:

1. **Identify the Reactants**:
The reaction given is:
\[ \text{Acetyl CoA} + \text{Oxaloacetic Acid} + \text{H}_2\text{O} \overset{\text{Citrate Synthase}}{\rightarrow} A + \text{CoA} \]
Here, the reactants are Acetyl CoA and Oxaloacetic Acid, along with water.

2. **Understand the Role of Enzyme**:
The enzyme involved in this reaction is Citrate Synthase. This enzyme catalyzes the condensation reaction between Acetyl CoA and Oxaloacetic Acid.

3. **Determine the Product**:
The product A formed from this reaction is Citrate. The reaction involves the combination of the two carbon atoms from Acetyl CoA and the four carbon atoms from Oxaloacetic Acid, resulting in a six-carbon compound, which is Citrate.

4. **Citrate Structure**:
The structure of Citrate can be represented as:
\[ \text{C}_6\text{H}_5\text{O}_7 \]
It contains three carboxyl groups (-COOH), making it a tricarboxylic acid.

5. **Confirm Characteristics of Compound A**:
- **First Product of TCA Cycle**: Citrate is indeed the first product formed in the TCA cycle.
- **Six-Carbon Compound**: Citrate is a six-carbon compound.
- **Undergoes Further Reactions**: Citrate can undergo further reactions, such as conversion to cis-aconitate in the presence of the enzyme aconitase.

6. **Conclusion**:
Based on the above analysis, we can conclude that compound A is Citrate, and the statements regarding it being the first product of the TCA cycle, being a six-carbon compound, and undergoing further reactions are all true.

### Final Answer:
The correct answer is that all statements about compound A (Citrate) are true.

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