Plastic Surgery>>>>>Basic principles and basic science
Question 1#

Which one of the following is true regarding collagen?

a. Its derivation is debated: either from the Greek for ‘strength’ or the Latin for ‘strand’
b. Type 1 collagen is formed from three identical ‘alpha’ chains
c. Type 3 collagen is formed from two different ‘alpha’ chains
d. Every third amino acid in collagen is glycine, the others usually being proline and hydroxyproline
e. Collagen is stabilized by polymerization

Correct Answer is D

Comment:

Every third amino acid in collagen is glycine, the others usually being proline and hydroxyproline. Collagen is derived from the Greek kolla (glue) and gennao (to produce) because when boiled, collagen forms glue. The fibrillar collagens, Type 1 and 3, are the most abundant types in skin. Type 1 is comprised of polypeptide chains which are arranged in a triple helix. Two of the chains making up Type 1 collagen are identical (alpha-1 chain), while the third chain is distinct (alpha-2 chain). Every third amino acid in the collagen molecule is glycine, resulting in the pattern Gly-X-Y with the X and Y positions occupied by proline and hydroxyproline. Stability is due to disulphide bonds and also cross-links formed as a result of de-amination of lysyl and hydroxylysyl residues. Type 3 collagen is expressed in greater quantities in scar and healing tissue, and Type 4 collagen is found in the basement membrane.