jimtrue.com : school : BSC2010L : Lab 04 - Enzymes

Posted by Jim True on February 5, 2004 7:01 AM. Last Updated October 22, 2006 9:23 PM

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Lab 04 - Enzymes

Introduction:

• Reaction is spontaneous but not necessarily rapid, reaction rate
  
• Example: Sugar --> Glucose + Fructose is very spontaneous but very slow reaction rate low.
  
• Due to Ea, energy of activation
  
• Each reaction -- 1st break down bonds (eA), 2nd forms new bonds.
  
• Each reaction -- requires energy input -- from surrounding environment, thermal, aborsorbed; collision faster; bonds are more likely to break
  
• Most biochemical reactions have high Ea, low rates can increase heat (temp) but will denature biomolecules
  
• Enzymes -- lower eA
  
• Enzyme -- bio catalyst
  
  • enzymes -- speed up reaction rates
    
  • Are selective for substrate
    
  • Activity can be controlled
  
  
• enzyme structure -- macromolecule -- protein -- 3-D Shape/Conformation, --specificity ~ shape
  
• Active Site -- region on enzyme that binds to substrate
  --Compatible fit of active site shape & substrate site.
  
• Enzyme-substrate complex
  --Brings reactant molecules in close/proper orientation
  --Stress bonds to destabilize reduces thermal energy needed
  -- Reaction takes place
  --Enzyme unaltered/reused
  
• Environmental Factors
  -- Temp, pH, Chemicals
  -- All can affect 3-D conformation
  -- Certain ranges -- optimal
  
• Temp -- up to certain temps enzyme mediated reaction rate increased; beyond optimal temperature rate decreased enzyme structure damaged/denatured.
  
• pH -- Optimal pH --> max reaction rate, lower or higher --> lower rates --> denature.
  
• Chemicals -- poisons & certain metabolic products inhibit/control enzyme activity.
  -- competitive inhibitor at active site
  -- noncompetitive inhibitor -- at allosteric site changes enzyme shape at the active site.

  Tonight's Exercize:
  Substrate -- Enzyme -- Product
  Catechol -- Catechol oxidase -- benzoquinone
  Colorless -- x -- yellow/brown (darker --> more activity)
  Supplied -- Potato

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