AP BIOLOGY

Detailed explanation-1: -The R groups have a variety of shapes, sizes, charges, and reactivities. This allows amino acids to be grouped according to the chemical properties of their side chains. For example, some amino acids have polar side chains that are soluble in water; examples include serine, threonine, and asparagine.

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: -Amino Acids with Hydrocarbon R-groups Except for phenylalanine, these are aliphatic hydrocarbons, containing no benzine ring. The simplest of the amino acids, glycine, has just a hydrogen atom in the position of the R-group.