Alpha helices and beta pleated sheets are common secondary structures in proteins that are stabilized by hydrogen bonding. The document discusses the primary, secondary, tertiary, and quaternary levels of protein structure, with a focus on how alpha helices and beta sheets form through hydrogen bonding between amino acids in the polypeptide backbone.

1. Protein Structure Alpha helices and Beta pleated sheets

2. Protein Structure Lesson Objectives To describe primary, secondary, tertiary and quaternary protein structures To describe the structure and formation of an alpha helix and a beta pleated sheet To describe the bonding that causes the structures to form and persist.

3. Summary Primary Structure Order of amino acids in a polypeptide chain (NH2 – COOH) Secondary Structure Folding of the polypeptide backbone Alpha helix and beta pleated sheet Stabilised by Hydrogen bonding between N-H and C=O

4. Summary Contd. Tertiary Structure Interactions between R groups Crucial to function Ionic bonds (Charged R groups) Hydrogen bonds (Polar R Groups) Dipole induced bonds (Non polar side chains) Covalent disulphide bridges (Cysteine)

5. Summary Contd. Quaternary Structure Two or more polypeptide chains grouped together