1.5 Amino acids - swatiri/Molecular-Biology GitHub Wiki

An amino acid is any organic molecule that consist of a basic amino group (―NH2), an acidic carboxyl group (―COOH), and an organic R group (or side chain) that is unique to each amino acid. The term amino acid is short for α-amino [alpha-amino] carboxylic acid. Each molecule contains a central carbon (C) atom, called the α-carbon, to which both an amino and a carboxyl group are attached. The remaining two bonds of the α-carbon atom are generally satisfied by a hydrogen (H) atom and the R group. Amino acids and proteins are the building blocks of life. Although amino acids serve other functions in cells, their most important role is as constituents of proteins.

Amino acids are linked to each other by peptide bonds, in which the carboxyl group of one amino acid is joined to the amino group of the next, with the loss of a molecule of water. Additional amino acids are added in the same way, by formation of peptide bonds between the free carboxyl on the end of the growing chain and the amino group of the next amino acid in the sequence. A chain made up of just a few amino acids linked together is called an oligopeptide (oligo=few) while a typical protein, which is made up of many amino acids is called a polypeptide (poly=many). The end of the peptide that has a free amino group is called the N-terminus (for NH2), while the end with the free carboxyl is termed the C-terminus (for carboxyl). The formula of a general amino acid is:

Types of Amino acids

Essential amino acids

These amino acids cannot be synthesized by the body. As a result, they must come from food. The 9 essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Nonessential amino acids

Nonessential amino acids are synthesized by the body, even if we do not get them from the food we eat. Nonessential amino acids include alanine, asparagine, aspartic acid, and glutamic acid.

Conditional amino acids

These are usually not essential, except in times of illness and stress. Conditional amino acids include arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine.