BIOMOLECULES AND ENZYMES

Detailed explanation-1: -The carbon, carboxyl, and amino groups are common to all amino acids, so the R-group is the only unique feature in each amino acid. (A minor exception to this structure is that of proline, in which the end of the R-group is attached to the -amine.)

Detailed explanation-2: -The amino acid backbone is identical on all amino acids, the R groups are different on all amino acids. For the structure of each amino acid refer to the figure below. There are 20 common amino acids found in proteins, each with a different R group (variant group) that determines its chemical nature.

Detailed explanation-3: -There are 20 amino acids that make up proteins and all have the same basic structure, differing only in the R-group or side chain they have. Amino acids are in an equilibrium between two acids with the proton (H+) moving between the amino group and the carboxyl group as shown below.

Detailed explanation-4: -The amino acids differ from each other in the particular chemical structure of the R group.

Detailed explanation-5: -Thus, the only amino acid listed that does not have a charged R group is asparagine, or answer a). Asparagine is a polar amino acid, as its side chain contains a polar amide group.