enzymes

• How do catalysts increase the rate of reaction?

  By lowering the activation energy
• What are enzymes?


  3D tertiary structure globular proteins who shape is determined by the primary sequence of amino acids
• Describe the induced fit model


  Initially enzymes aren’t complementary to their substrate. When the enzyme and substrate bind they form an enzyme-substrate complex and the structure of the enzyme is altered so that the active site of the enzyme fits around the substrate.
• Describe the way temperature effects rate of reaction


  Rate of reaction increases up to the optimum temperature as the kinetic energy of the enzyme increases above this the rate of reaction decreases because the enzyme becomes denatured
• what happens to the rate of reaction when the enzyme is denatured?


  The rate of reaction decreases
• How does pH affect rate of reaction?


  PH affects the enzyme shape so each enzyme has an optimum pH. Either side of this the rate of reaction has not reached its peak.
• What is pH?

  A measure of the hydrogen ion concentration
• Why does pH affect an enzyme?

  It can disrupt the bonds in the tertiary structure
• how does enzyme concentration affect rate of reaction?

  Rate of reaction increases as enzyme concentration increases however past a certain point it has no effect on rate of reaction as it becomes the limiting factor
• How does substrate concentration affect rate of reaction?

  As concentration of substrate increases rate of reaction increases however beyond certain point it has no effect as it becomes the limiting factor
• what are competitive inhibitors?


  molecules that have a similar shape to the substrate and bind to the active site
• How does a competitive inhibitor work?


  It binds to the active site of the enzyme, preventing the substrate from binding
• What effect do competitive inhibitors have on rate of reaction?


  They decrease the rate of reaction until a certain point when they have no effect
• Why can increasing substrate concentration reverse competitive inhibition?


  The substrate eventually dilutes the inhibitor so that all enzyme molecules bind to the substrate
• Is competitive inhibition reversible?


  Yes
• What is non-competitive inhibition?


  When a molecule binds to the allosteric site and changes the shape of the active site
• What effect does non-competitive inhibition have on rate of reaction?


  It decreases the reaction rate
• Why does non-competitive inhibition decrease the reaction rate?


  Because it cannot be reversed by increasing the substrate concentration, therefore enzymes cannot bind to substrates
• What does anabolic mean?


  Building up molecules, e.g. protein synthesis
• What does catabolic mean?


  Breaking molecules down, e.g. digestion
• What is an enzyme substrate complex?


  A temporary bond between an enzyme and its substrate
• What is the shape of an active site determined by?

  It’s tertiary structure
• What are the two models of enzyme action and which one is correct?

  Lock and key theory and induced fit model. Induced fit model is correct.
• What does intracellular mean?


  Located or occurring within a cell
• What does extracellular mean?


  Located or occurring outside of cell