Question

If the basic formula of an α-amino acid is R-CH(NH2)-COOH, where R is the side chain, what is the primary point of distinction between any two proteins?

(a) Number of amino groups

(b) Number of carboxyl groups

(c) The side chain R

(d) Relative positions of amino, carboxyl groups and R

I had been asked this question in final exam.

My doubt stems from Biomolecules in division Biomolecules of Chemistry – Class 12

Answer 1

Correct option is (c) The side chain R

The best explanation: α-amino acids are the constituents of proteins. Different proteins are formed by polymerisation of different α-amino acids, which are formed due to the difference in the side chain substituted group R, which may be as simple as hydrogen or as complex as imidazole.