Question

Identify a side chain (R) group present in Leucine, an amino acid.

• A. H$-$
• B. $-$CH$_3$
• C. Me$_2$CH$-$
• D. Me$_2$CH $-$ CH$_2-$

Hint:

Leucine and Isoleucine are isomers; Leucine has an isobutyl group, while Isoleucine has a sec-butyl group.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We need to identify the specific alkyl group ($R$) attached to the alpha carbon in the amino acid Leucine.
Step 2: Detailed Explanation:
1. Glycine: $R = -H$
2. Alanine: $R = -CH_3$
3. Valine: $R = -CH(CH_3)_2$ (Isopropyl group, written as $Me_2CH-$)
4. Leucine: $R = -CH_2CH(CH_3)_2$ (Isobutyl group, written as $Me_2CH-CH_2-$)
Step 4: Final Answer:
The side chain of Leucine is the isobutyl group, $Me_2CH-CH_2-$.