Amino acid abundant in collagen:
So the core concept here is the structure of collagen. Collagen is a triple helix made up of three polypeptide chains. The primary amino acids are glycine, proline, and hydroxyproline. Glycine is the most abundant, making up about one-third of the amino acids because of the repeating Gly-X-Y sequence, where X is often proline and Y is hydroxyproline.
Why is glycine the right answer? Because of its small size, allowing the tight triple helix structure. The glycine residues are in every third position, which is crucial for the stability of collagen. Proline and hydroxyproline contribute to the structure too, but glycine is the most abundant by number.
The wrong options might include other amino acids like lysine, alanine, or glutamine. For example, lysine is involved in cross-linking but isn't as abundant. Alanine is a common amino acid but not specific to collagen. Glutamine isn't a major component here.
Clinical pearl: Remember the Gly-Pro-Hyp sequence in collagen. Deficiency in vitamin C leads to impaired hydroxylation of proline to hydroxyproline, causing scurvy. So, the high yield fact is the role of glycine and vitamin C in collagen synthesis.
Putting it all together, the correct answer is glycine. The explanation should cover the structure, the role of each amino acid, and why others are incorrect. Also, mention the clinical correlation with vitamin C deficiency.
**Core Concept**
Collagen, the most abundant protein in mammals, contains a high proportion of glycine due to its structural role in the triple-helical collagen molecule. The repeating **Gly-X-Y** sequence (where X is often proline and Y is hydroxyproline) is critical for stabilizing the collagen fibril.
**Why the Correct Answer is Right**
**Glycine** is the most abundant amino acid in collagen, comprising ~33% of its total content. Its small side chain (a single hydrogen atom) allows tight packing of the triple-helical structure, which is essential for collagen's tensile strength. The **Gly-Pro-Hydroxyproline** motif is repeated throughout the molecule, with glycine's minimal steric hindrance enabling the helix to form without distortion.
**Why Each Wrong Option is Incorrect**
**Option A:** *Alanine* is a common amino acid but lacks the structural role in collagen. Its larger side chain would destabilize the triple helix.
**Option B:** *Lysine* is involved in collagen cross-linking but is present in much lower amounts (~5%) compared to glycine.
**Option D:** *Glutamine* is not a major component of collagen; its side chain cannot stabilize the triple-helix structure.
**Clinical Pearl / High-Yield Fact**
Remember the **Gly-Pro-Hyp** triad in collagen. Vitamin C deficiency impairs hydroxylation of proline