2b. Proteins and enzymes

• What are amino acids made up of

  Amine group

  carboxyl group

  side chain
• What do two amino acids form

  Dipeptide
• What bond forms between amino acids

  Peptide bonds
• What type of reaction is two amino acids joining

  condensation
• What is the primary structure of a protein

  Sequence of amino acids
• What is the secondary structure of amino acids

  folding of the polypeptide chain in certain areas due to hydrogen bonds. Forms either an alpha helix or a beta pleated sheet
• What is the tertiary structure of a protein

  Further folding into final shape due to hydrogen, ionic and disulphide bonds
• What is the quaternary structure

  Only in proteins made of more than one polypeptide chain.
• Why bonds break first when a protein is heated

  Hydrogen
• What are the two protein shapes

  Fibrous - collagen

  globular - enzymes
• How do we test for proteins in a sample

  add biuret solution, if protein is present it goes from blue to lilac
• What is the Rf value in chromatography

  Distance from origin to spot divided by origin to solvent front
• What are enzymes

  biological catalysts that lower the activation energy
• What is activation energy

  Energy required for a reaction to occur
• Why can enzymes be reused

  Don’t undergo permanent structural changes
• Explain the lock and key model

  Substrate combined with enzyme at active side in a precise way and the active site is always the complementary shape
• What is the limitation of the lock and key model

  The enzyme is considered a rigid structure however it isn’t
• What is the induced fit model

  The idea that the active site of an enzyme goes through a change in shape. the amino acids are moulded to wrap around the substrate.
• How do we measure rate of reaction

  Amount of product / time taken
• Why on a graph does the rate of reaction slow down with enzymes

  More substrate at the start
• How does temperature affect enzymes

  As temp increases molecules collide more often due to kinetic energy.
• What happens to enzymes above a temp of 40

  The hydrogen bonds and ionic bonds in the tertiary structure will break causing a change in shape. Active site is no longer complementary so denaturing occurs
• the greater the concentration of h+ ions the …………. the Ph

  Lower
• How does a change in ph affect the enzymes

  Causes a change in the charge of amino acid so causes some of the bonds to break changing the tertiary structure
• What are the two types of inhibitors

  Competitive and non competitive
• How does competitive inhibition work

  The inhibitor has a similar shape to the active site so will bind to it and fewer enzyme substrate complexes will form
• How does non competitive inhibition happen

  The inhibitor binds to a different part of the enzyme causing a change in the tertiary structure and the active site changes shape