Structure

All amino acids have a similar chemical structure—each contains an amino group (NH2), an acid group (COOH), a hydrogen atom (H), and a distinctive side group that makes proteins more complex than either carbohydrates or lipids. All amino acids are attached to a central carbon atom (C).

The distinctive side group identifies each amino acid and gives it characteristics that attract it to, or repel it from, the surrounding fluids and other amino acids. Some amino acid side groups carry electrical charges that are attracted to water molecules (hydrophilic), while others are neutral and are repelled by water (hydrophobic). Side-group characteristics (shape, size, composition, electrical charge, and pH) work together to determine each protein's specific function.

TABLE OF ESSENTIAL AND

Essential amino acids

NONESSENTIAL AMINO ACIDS

Nonessential amino acids

Histidine

Alanine

Isoleucine

Arginine

Leucine

Asparagine

Lysine

Aspartic acid

Methionine

Cysteine

Phenylalanine

Glutamic acid

Threonine

Glutamine

Tryptophan

Glycine

Valine

Proline

Serine

Tyrosine

The three-dimensional shape of proteins is derived from the sequence and properties of its amino acids and determines its function and interaction with other molecules. Each amino acid is linked to the next by a peptide bond, the name given to the link or attraction between the acid (COOH) end of one amino acid and the amino end (NH2) of another. Proteins of various lengths are made when amino acids are linked together in this manner. A dipeptide is two amino acids joined by a peptide bond, while a tripep-tide is three amino acids joined by peptide bonds.

The unique shapes of proteins enable them to perform their various tasks in the body. Heat, acid, or other conditions can disturb proteins, causing them to uncoil or lose their shape and impairing their ability to function. This is referred to as denaturation.

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