Objectives

E – Recall the different structures of proteins and the test for proteins.

C – Describe how a peptide bond is formed. Describe the

different structure of proteins

A – Explain how the structures of a polypeptide build up and how changes to this may affect function

Proteins

 • Polymer • Monomer is amino acid

• 20 amino acids

Amino group Carboxylic group

Amino acids

• 20 different amino acids

• Joined together by condensation

• Peptide bond is formed

• Polypeptide is many amino acids joined together

condensation

Polypeptide – primary structure

• Chain of amino acids

• Held together by peptide bonds

• Differences due to the type, number and position of amino acid

Secondary structure

Folding of polypeptide chain forming an alpha helix or a

beta sheet

Secondary structure

Held together by hydrogen bonds

Tertiary structure

Further folding of secondary structure, held together by hydrogen, ionic, disulphide and hydrophobic bonds

Quaternary structure

More than one polypeptide joined together

The alpha helix are shown

The beta pleated sheets are shown

The disulphide bridges are shown by purple atoms bonded together.

The bits of the protein chain which are just random coils and loops are shown as bits of "string".

Monosaccharide 1-4 glycosidic link

Maltose

Fructose

Sucrose

Galactose

Hexose

Condensation

Hydrolysis

Peptide bond

Tertiary structure

Secondary structure

Secondary structure Lactose

Lactose

Primary structure

Quartenary structure

Hydrogen bonds

Alpha helix

Beta pleated sheet