Proteins

Proteins have many specialised structures to help in their functions
1. Antibodies
2. Enzymes
3. Transport Proteins
4. Structural Proteins
Food Testing for Proteins
1. Biuret Test
  1. Add sodium hydroxide to make solution akali
  2. Add Copper(II) sulfate solution
    1. Purple is positive protein result
    2. Negative result will cause the solution to remain blue
Proteins are made up of one or more polypeptides
1. Monomer of proteins are amino acids
  1. Dipeptide formed from two amino acids joined
    1. Polypeptides are formed when more than two amino acids are joined
2. Amino acids are joined by condensation reactions
  1. Water molecule 'released' during reaction
    1. Peptide bonds are formed between amino acids
  2. Hydrolysis is the reverse reaction
Proteins have four structural levels
1. Quaternary
  1. Several polypeptide chains bonded together
  2. Final 3D structure
2. Primary
  1. Sequence of amino acids forming a polypeptide chain
3. Secondary
  1. Polypeptide chain begins to coil into a alpha helix or a beta pleated sheet
    1. Because of hydrogen bonding within the chain
4. Tertiary
  1. The folding from the secondary structure causes more bonding to different parts of the chain
    1. More hydrogen bonds form, ionic bonds start
      1. Final structure for single polypeptides
    2. Disulfide bridges form between 2 molecules of the amino acid crysteine

Resource summary

	Created by Dominic Weston over 6 years ago