Proteins

• Monomers of proteins

  Amino Acids
• Amino Acid structure

  Amino group (NH2)

  Central C with H and R group Carboxyl group (COOH)
• How do AA join into dipeitides

  Condensation reaction forming peptide bonds and releasing water molecule

  Peptide bond forms between amine group of one AA and the carboxyl group of the other
• Test for proteins (peptide bond)

  -Add Biuret reagent

  -If proteins (peptide bond) present, turns from blue to lilac/purple
• Primary structure

  Amino acids joined together by peptide bonds
• Secondary structure

  -Folding into alpha helix or beta pleated sheets

  -Using hydrogen bonds bewteen amino acids

  -Peptide bonds still present
• Tertiary structure

  -Further folding of polypeptide sometimes into a globular structure

  -using ionic and disulfide bonds sometimes

  -Hydrogen and peptide bonds still present
• Quaternary structure

  -Interactions between multiple polypeptide chains (sometimes including a prosthetic group, like haem in haemoglobin)

  -Still involves peptide, hydrogen, ionic and disulfide bonds
• Compliamentary and specific

  Complimentary- able to fit/bind

  Specific- which substrates will fit into an active site i.e only one substrate to one particular active site
• Induced fit model

  -Substrate is complimentary to specific active site of enzyme

  -enzyme's active site changes shape to fit around the substrate more easily

  -lowers activation energy because: holds substrate molecules closer together so they react more easily strain on the bonds so hydrolysis occurs more easily
• Inhibitors

  -slow down chemical reaction

  -by reducing number of ESCs formed

  -specific to just one enzyme

  -competitive or non-competititve
• Competitive Inhibitors

  -similar shape to normal substarte so can bind to an enzymes active site and block substrate

  - preventing ESC formation

  -Effects can be overcome by adding more substrate

  -reversible- blocking is temporary
• Non-competitive inhibitors

  -bind to a site away from the active site of an enzyme and causes tertiary structure to change shape

  - so active site denatures and ESCs cannot form

  -effects cant be overcome by adding more substrate

  -irreversible- permanently denatured active site