Enzymes
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Enzymes

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Enzymes Enzymes Presentation Transcript

  • ENZYMES
    • made of proteins
    • biological catalysts (speed up reactions)
    • act on molecules (substrate) to break them down/build them up
    • most enzymes’ names end in –ase
  • Anatomy of an enzyme
  • How Enzymes Work
    • Induced Fit Model
    • Active site on enzyme draws substrate(s) closer (attracted by functional gp)
    • Active site shaped to only bind to a specific substrate(s), like lock and key
    • Sub(s) get drawn into cleft of enzyme
    • Once bound, Enzyme-Substrate Complex (ES Complex) is formed.
    • ES Complex changes shape slightly either breaking or binding sub. molecule(s)
    • End product released and enzyme returns to original shape, able to bind more sub.
    • YouTube - Enzyme
  • Activation Energy
    • the amount of energy (without enzymes) needed to start a reaction (usually high)
    • enzymes lower amnt of activation energy needed
  • Enzyme Co-factors
    • non-protein component of enzymes
    • help enzyme to catalyze by binding to active site or substrate
    • 2 types:
      • Co-enzymes – organic molecules
    • - ex. NAD + (vitamin B derivative)
      • Inorganic Ions – ex. Ca 2 +, Zn 2 +…
  • Enzyme Inhibitors
    • Inhibit (slow down/stop) enzyme activity
    • This prevents build up of wastes in cell
    • 2 kinds:
    • Reversible - controls enzyme activity by action on either substrate or end product
    • Irreversible – permanently destroys active site
  • Reversible Enzyme Inhibitors
    • 3 types
    • Competitive Inhibitor – binds to active site to prevent substrate from binding
    • Video: enzyme (biochemistry) :: Competitive inhibitors prevent enzymes from catalyzing with substrates -- Britannica Online Encyclopedia
    • ii) Noncompetitive Inhibitor – binds somewhere other than active site, causes enzyme to change shape and slow down reaction
    • Tutorial 6.1 Enzyme Catalysis
    • iii) Allosteric Enzyme Inhibitor – binds to enzyme somewhere other than active site, causing enzyme to change shape and stops reaction
    • Tutorial 6.2 Allosteric Regulation of Enzymesl
  • Irreversible Enzyme Inhibitors
    • permanently destroys active site
    • ex. Some heavy metals like Hg, Cd, Pb, As
  • Regulation of Enzyme Activity
    • Feedback Inhibition
      • a product formed in a sequence of reactions inhibits an enzyme that catalyzes a substrate earlier in the reaction
      • inhibitor binds to enzyme, slowing down production (non-competitive inhibitor)
      • as production slows down, amount of inhibitor available decreases until used up
      • so enzyme can start binding and producing again
      • soon amount of inhibitor in product increases enough to inhibit production again
      • continues in a constant loop to control the reaction
      • Feedback Inhibition of Biochemical Pathways
      • 2. Location of Enzyme
      • some enzymes kept in cellular compartments until needed