Enzymes

• Biological Catalyst


  Function in living systems, speed up rate of chemical reactions without being used up or undergoing permanent change
• Catalyst


  A chemical which speeds up the rate of chemical reactions without being used up or undergoing permanent change
• Metabolic Pathway


  A sequence of enzyme-catalysed reactions that lead to the conversion of a substance into a final product
• Globular Protein


  • A class of spherical shaped proteins that are generally water soluble and typically have metabolic roles
• Intracellular enzyme


  Enzyme that is produced and functions indie a cell
• Extracellular enzyme


  Enzyme that is secreted by cells and catalysed reactions outside cells
• Intracellular reaction


  A reaction that occurs within cells
• Extracellular reaction


  A reaction that occurs outside of cells
• Catalase


  • An enzyme that catalyses the intracellular breakdown of hydrogen peroxide into oxygen and water
• Amylase


  • An enzyme that catalyses the extracellular breakdown of starch
• Trypsin


  • An enzyme that catalyses the extracellular breakdown of proteins
• Enzyme-substrate complex


  The temporary complex formed when the substrate binds to the active site of the enzyme
• Denatured


  The active site has changed so is no longer complementary to the substrate
• Lock and Key hypothesis

  A model of enzyme action that described how the enzyme will only fit a substrate that has the correct complementary shape to the active site
• Induced fit hypothesis


  A model of enzyme action that describes how once a specific substrate binds to the active site, the enzyme undergoes subtle conformational changes to fit the substrate better
• Enzyme-product complex


  The temporary complex formed after the enzyme has catalysed the reaction but before the products have left the active site of the enzyme
• Activation energy


  The amount of energy needed for a reaction to happen
• Vmax


  maximum velocity, maximum rate of reaction
• Competitive inhibitors


  An inhibitor which has a similar shape to that of the substrate molecules and therefore complete with the substrate for the active site
• Non- competitive inhibitors


  An inhibitor which binds to the enzyme at an alternative site, which alters the shape of the active site and therefore prevents the substrate from binding to it
• Cofactors


  Simple molecules of inorganic ions
• Coenzymes


  Larger organic cofactors
• Prosthetic group


  A cofactor which is a permanent part of the structure of an enzyme
• Temperature coefficient


  The ratio between the rates of that reaction at two different temperatures
• Cyanide


  • A metabolic poison which acts as an irreversible inhibitor of cytochrome oxidase and hence preventing respiration
• End-product inhibition


  A method of enzyme inhibition where the product of an enzyme controlled reaction can bind to the enzyme and prevent it from working
• Inactive precursor


  An inactive form of an enzyme that cannot carry out its function unit it is activated