proteins

• amino acids 


  condensation reaction

  
• peptide bond

  -covalent bond formed between 2 amino acids

  -water is removed when bond forms= condensation reaction

  -takes place in ribosomes, using peptidyl transference

  • dipeptide= 2 amino acids joined together
  • tripeptide= 3 amino acids joined together
  • polypeptide= many amino acids joined together
• primary structure

  -order of amino acids within polypeptide chain

  • order controlled by DNA, chain put together by ribosomes
  • held by peptide bonds
• secondary structure

  -polypeptide chain twists up to form secondary structure (helix or B-strand)

  • held by hydrogen bonds
• tertiary structure

  -3D coils structure

  • held by hydrogen, disulphide, ionic bonds, hydrophobic, hydrophilic interactions
• quaternary structure

  -2 or more polypeptide chain come together to form protein

  • held by ionic, hydrophobic, hydrophilic, hydrogen and disulphide bonds.
• Fibrous protein

  = formed from long, insoluble molecules due to high proportion of amino acids. They offer structural support to cells.

  • collagen= roughly 30% of the protein in the body is collagen- found in ligaments, tendons, muscle, cartilage, bone and skin.
  • keratin= crucial to maintaining the structure of horns, claws, hooves, hair and skin- the degree of disulphide bonds determines the flexibility.
  • elastin= found in connective tissue and is what allows our skin to return to it's normal appearance after being pinched.
• testing for proteins 


  = biuret

  • violet colour forms is protein is present