Amino-acid expressed maximally in collagen?
**Core Concept**
Collagen is the most abundant protein in the human body, providing structural support and elasticity to skin, bones, tendons, and ligaments. The amino acid composition of collagen is unique, with certain amino acids being present in higher concentrations than others.
**Why the Correct Answer is Right**
The correct amino acid expressed maximally in collagen is **Glycine**. Glycine is the smallest amino acid and is essential for the formation of the triple helix structure of collagen. It occupies every third position in the collagen polypeptide chain, allowing for the tight packing of collagen fibers. The high concentration of glycine in collagen is necessary for its proper folding and stability.
**Why Each Wrong Option is Incorrect**
**Option A:** Proline is another essential amino acid in collagen, but it is not the amino acid expressed maximally. Proline is crucial for the formation of collagen's helical structure, but its concentration is lower than that of glycine.
**Option B:** Hydroxyproline is a modified amino acid found in collagen, but it is not the amino acid expressed maximally. Hydroxyproline is formed by the post-translational modification of proline residues and is essential for the stability of collagen fibers.
**Option C:** Alanine is a non-essential amino acid present in collagen, but it is not the amino acid expressed maximally. Alanine is not as critical for the structure or function of collagen as glycine.
**Option D:** Glutamic acid is a non-essential amino acid present in collagen, but it is not the amino acid expressed maximally. Glutamic acid is not as essential for the structure or function of collagen as glycine.
**Clinical Pearl / High-Yield Fact**
Glycine's unique structure and high concentration in collagen make it a crucial component of connective tissue. Deficiencies in glycine can lead to conditions such as osteoporosis and skin fragility.
**Correct Answer:** C. Glycine