1. Proteins Basic structure of an amino acid

2. Forming DIPEPTIDES Two amino acids join by a condensation reaction (elimination of water) as the amino group of one amino acid forms a peptide bond with the carboxyl end of another. A DIpeptide is formed. (Many build up in a linear sequence i.e. a POLYpeptide chain.)

3. amino acid + amino acid dipeptide + waterH

4. Different types of bonds in protein structure

5. Polypeptides are held in position by these various bonds.

6. Protein structures

7. Tertiary: - the polypeptide helix is bent and twisted into a compact 3D shape This is held together by the 3 different types of bonds (ionic, disulphide,hydrogen) e.g. globular proteins such as enzymes.

8. Quaternary: - a combination of two or more polypeptides chains in tertiary form. These chains are held in position by ionic, disulphide and hydrogen bonds They may include non-protein groups such as minerals and form large complex molecules e.g. haemoglobin (4 polypeptide chains and iron)

9. Denaturing proteins