Enzymes

    Cards (25)

    • What is an enzyme?
      An enzyme is a protein that acts as a catalyst in biological reactions, speeding up the rate of the reaction without being consumed in the process
    • How do enzymes catalyse reactions?
      Lowering activation energy
    • Why do enzymes lower activation energy?
      • Hold together the molecules and reducing repulsion
      • Putting strains on substrate bonds so they are broken more easily
    • What is the lock and key model?
      Specific binding of a substrate to an enzyme's active site
    • What is the induced fit model?
      Active site of enzyme changes shape slightly after substrate has binded to it
    • What are the properties of enzymes?
      • Usually catalyse one reaction
      • Tertiary structure determines shape of active sites
    • How can we measure enzyme activity?
      • How fast the product is made
      • How fast the substrate is broken down
    • What are the factors affecting enzyme activity?
      • Temperature
      • pH
      • Enzyme concentration
      • Substrate concentration
    • How does temperature affect enzyme activity?
      • Increased kinetic energy for substrate molecules
      • More collisions with active sites
      • If temp exceeds optimum enzyme denatures
    • How does pH affect enzyme activity?
      • Above and below optimum pH the H+ and OH- ions disrupt enzyme bonds
      • Active site denatures
    • How does substrate concentration affect enzyme activity?
      • More substrates means more collisions with enzymes
      • Saturation point (all active sites are full)
    • How does enzyme concentration affect enzyme activity?
      • More enzymes means more collisions with substrate
      • Saturation point when (all substrates have bonded)
    • What is an enzyme inhibitor?
      A substance that decreases its activity of an enzyme
    • What is a competitive inhibitor?
      A molecule with a similar shape to the substrate that binds to the enzyme instead
    • What is a non-competitive inhibitor?
      Molecule that binds to an enzyme away from active site, changing enzyme structure so substrate is unable to bind
    • What are the 2 ways we can use to measure the rate of an enzyme controlled reaction?
      • Measure how fast the product of the reaction appears
      • Measure how fast the substrate is broken down
    • Measuring the effect of temperature on product formation (catalase and hydrogen peroxide)
      • Set up boiling tubes containing same volume and concentration of hydrogen peroxide
      • Add equal amounts of buffer solution to each boiling tube so pH remains constant
      • Put boiling tubes in different temp water baths
      • Use a pipette to add same volume and concentration of catalase to each boiling tube then attach bung and deliver tube
      • Record how much oxygen is produced in the first minute
      • Repeat the experiment 3 times at each temp
      • Calculate mean volume of oxygen produced at each temp
      • Calculate mean rate of reaction at each temp
    • Measuring effect of temp on product formation (catalase and hydrogen peroxide)

      Apparatus:
    • Measuring the effect of enzyme concentration on substrate breakdown (amylase and maltose)
      • Put a drop of iodine in potassium iodide solution into each well in the spotting tile
      • Label each well
      • Mix together a known concentration of amylase and starch in a test tube
      • Use a pipette to drop the amylase/starch mixture in each well at regular intervals
      • Observe resulting colour
      • How fast amylase is working=how long it takes for iodine solution to no longer change colour when starch/amylase mixture is added
      • Repeat experiment with different amylase concentrations
      • Repeat experiment 3 times at each amylase concentration
      • Calculate mean time taken for each amylase concentration
    • Measuring effect of enzyme concentration on substrate breakdown (amylase and maltose)
      Apparatus:
    • How do we estimate initial rate of reaction?
      • Draw a tangent at t=0
      • Calculate the gradient of the tangent
      • Unit= y-axis unit/x-axis unit
    • Temperature effect on on rate of enzyme-controlled reactions
      Graph:
    • pH effect on rate of enzyme-controlled reaction 

      Graph:
    • Substrate concentration effect on rate of enzyme-controlled reactions
      Graph:
    • Enzyme concentration effect on rate of enzyme-controlled reactions 

      Graph:
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