Proteins

• monomer of proteins are amino acids
• a dipeptide is formed when two amino acids join together
• a polypeptide is when more than two amino acids join together
• proteins are made of one or more polypeptides
• an amino acid is made up of an R group, carboxyl group (COOH) and an amine group.
• there are 20 amino acids
• the bond between amino acids are peptide bonds
• proteins have primary, secondary, tertiary and quaternary structures.
• the primary structureis a polypeptide chain made up amino acids.
• secondary structure is when hydrogen bonds form between amino acids, causing the polypeptides to coil into an alpha helix or fold into a beta pleated sheet.
• tertiary structure is when proteins form globular shapes due to hydrogen bonds and disulphide bridges.
• quaternary structure is where multiple polypeptides join together by bonds, creating a 3D structure.
• The test for proteins is the biuret test, add sodium hydroxide solution (alkaline) to the food sample, then add copper (II) sulphate solution. Positive result (protein present) - blue to purple.