Question

The primary amino acids generally present in mammalian proteins are

• A. Alpha (\(\alpha\)) D- amino acids
• B. Beta (\(\beta\)) D- amino acids
• C. Beta (\(\beta\)) L- amino acids
• D. Alpha (\(\alpha\)) L- amino acids

Hint:

Remember: "L" for "Life". Almost all naturally occurring proteins in eukaryotic life are constructed exclusively from L-enantiomers of \(\alpha\)-amino acids.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Amino acids exist as stereoisomers (enantiomers) designated as D- or L- forms based on their spatial configuration relative to glyceraldehyde.

Step 2: Detailed Explanation:
In living organisms, particularly mammals, ribosomal protein synthesis utilizes a highly specific set of 20 standard amino acids.
1. These amino acids are almost exclusively of the L-configuration (chiral center configuration matching L-glyceraldehyde).
2. Furthermore, they are alpha (\(\alpha\))-amino acids, meaning both the amino group (\(-\text{NH}_2\)) and the carboxylic acid group (\(-\text{COOH}\)) are covalently attached to the same central carbon atom (the \(\alpha\)-carbon).
D-amino acids are generally absent from mammalian proteins, although they do occur in certain bacterial cell walls and peptide antibiotics.
Therefore, standard mammalian proteins are composed of \(\alpha\)-L-amino acids.

Step 3: Final Answer:
The correct option is 4, which corresponds to Alpha (\(\alpha\)) L- amino acids.