The amimo acid in which R group is -` CH_2CH_2COOH` is

Options

A. aspartic acid
B. glutamic acid
C. valine
D. threonine

Answer

To determine the amino acid with the R group -CH2CH2COOH, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of Amino Acids**:
- Amino acids have a general structure that includes an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable R group (side chain).
- The R group is what differentiates one amino acid from another and can vary in structure and properties.

2. **Identifying the R Group**:
- The given R group is -CH2CH2COOH.
- This indicates that the R group consists of two carbon atoms (CH2CH2) followed by a carboxylic acid group (COOH).

3. **Analyzing the R Group**:
- The presence of the -COOH group in the R chain suggests that this amino acid is likely to be acidic in nature.
- The structure of the R group can be broken down as follows:
- CH2 (first carbon)
- CH2 (second carbon)
- COOH (carboxylic acid group)

4. **Comparing with Known Amino Acids**:
- We can compare this structure with known amino acids:
- Aspartic acid has the R group -CH2COOH.
- Glutamic acid has the R group -CH2CH2COOH.
- Valine has the R group -CH(CH3)2.
- Threonine has the R group -CHOHCH3.
- From this comparison, we can see that the R group -CH2CH2COOH corresponds to glutamic acid.

5. **Conclusion**:
- Therefore, the amino acid with the R group -CH2CH2COOH is **Glutamic Acid**.

### Final Answer:
**B. Glutamic Acid**