proteins

• amino acids make up polypeptide chains/proteins
• amino acid

  A) amino

  B) side chain

  C) carboxyl

  
• proteins can be grouped into two classes based on their functions:

  • globular
  • structural
• all proteins contain nitrogen, carbon, hydrogen, and oxygen. some also contain sulphur
• primary structure is the number and sequence of amino acids in a polypeptide chain
• secondary structure describes the way the polypeptide chain folds or coils into alpha helixes and beta pleated-sheets. This is maintained by hydrogen bonds
• tertiary structure is the further folding of the polypeptide chain into a specific complex 3d structure
• tertiary structure is held together by bonds between R groups of different amino acids and disulphide bonds between sulfur containing amino acids
• tertiary structure is maintained by 3 different types of bonds:

  • hydrogen bonds
  • ionic bonds
  • disulphide bridges
• quaternary structure consists of two or more polypeptide chains joined together
• test for protein:

  1. add biuret reagent
  2. a positive result - colour change is blue to violet if peptide bonds are present
• Describe the structure of proteins

  1. polymer of amino acids
  2. joined by peptide bonds
  3. formed by condensation
  4. primary structure is order of amino acids
  5. secondary structure is folding of polypeptide chain due to hydrogen bonding
  6. tertiary structure is 3D folding due to hydrogen, ionic and disulphate bonds
  7. quaternary structure is two or more polypeptide chains