1.4.1 Proteins

Describe/ draw the general structure of an amino acid

COOH = carboxyl group

R = variable side cahin

H2N = amine group

How many amino acids are common in all organisms? how do they vary?

The 20 amino acids that are common in all organisms differ only in their side group (R)

Describe how amino acids join together

• condensation reaction

• removing a water molecule

• between carboxyl / COOH group of one and the amine NH2 group of the other

• forming a peptide bond

What are dipeptides and polypeptides?

Dipeptide - 2 amino acids joined together

Polypeptide - many amino acids joined together

Describe the primary structure of a protein

Sequence of amino acids in a polypeptide chain, joined by peptide bonds

Describe the secondary structure of a protein

• folding (repeating patterns) of a polypeptide chain eg. alpha helix / beta pleated sheets

• due to hydrogen bonding between amino acids

• between NH (group of amino acid) and C=O (group)

describe the tertiary structure of a protein

• 3D folding of polypeptide chain

• due to interactions between amino acid R groups (dependent on sequence of amino acids)

• forming hydrogen bonds, ionic bonds and disulfide bridges

Describe the quaternary structure of a protein

• more than one polypeptide chain

• formed by interactions between polypeptides (hydrogen bonds, ionic bonds, disulfide bridges)