Amino acids, peptides and proteins

Structure of an amino acid.

alpha carbon, carboxyl group (COO-), Amino group (NH3+) and a side chain (R group).

How are amino acids categorised.

Categorised by their R groups: nonpolar, aliphatic, polar, uncharged, aromatic, positively and negatively charged. These influence the solubility of the amino acid in water.

Formation of a peptide bond.

Two amino acids join in a condensation reaction, releasing a H₂O molecule. OH- from carboxyl group and H+ from Amino group.

Peptides

Chains of amino acids.

Dipeptide

Two amino acids joined together.

Oligopeptide.

A few amino acids joined together.

Differences between the different levels of a protein structure.

Primary: sequence of a chain of amino acids

Secondary: Local folding of the polypeptide chain into helices or sheets.

Tertiary: 3D folding pattern of a protein due to side chain interactions.

Quaternary: more than one amino acid chain.

Which amino acids with aromatic groups can absorb UV light?

Tryptophan, tyrosine and phenylalanine

Conjugated proteins

Proteins that contain chemical components in addition to amino acids.

Prosthetic group

The non amino acid part of a conjugated protein, which usually plays an important role in the biological role of the protein.