AP BIOLOGY

Detailed explanation-1: -The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. The nonessential amino acids are alanine, asparagine, aspartic acid, glutamic acid, and serine.

Detailed explanation-2: -The Twenty Amino Acids. NB1-The images and interactive molecules from both lists below are referenced directly from Klotho, the Biochemical Compounds Declarative Database at the Institute of Biomedical Computing, Wahington University. NB2-Here is a text document giving amino acid side chain representations.

Detailed explanation-3: -Amino acids differ from each other with respect to their side chains, which are referred to as R groups. The R group for each of the amino acids will differ in structure, electrical charge, and polarity.

Detailed explanation-4: -The 20 standard amino acids encoded by the Genetic Code were adopted during the RNA World, around 4 billion years ago. This amino acid set could be regarded as a frozen accident, implying that other possible structures could equally well have been chosen to use in proteins.