Enzyme Action

Enzymes
1. Work intracellular, in the cell, and extracellular, outside the cell
2. Lock and Key model
  1. substrate fits the active site like a key in a lock
    1. however its found that the enzyme substrate complex changed shape slightly
      1. 'Induced fit' a better theory
        substrate has to make the active site change its shape to fit specifically for the substrate
3. Properties of enzymes structure
  1. Related to tertiary strcuture
    1. active site due to tertiary which itself is due to primary
      1. Each enzyme different
      2. Mutations of gene may change enzyme produced
  2. very specific, catalyses one reaction
    1. as one complementary substrate fits
Factors Affecting Enzymes
1. Temperature rises, causing molecules to vibrate more
  1. if temperature goes too high,
    1. Breaks some bonds within the enzyme so it loses shape
      1. Enzyme becomes denatured, loses function as an enzyme
2. pH, most enzymes optimum at 7 pH
  1. Exceptions e.g. pepsin at pH 2
  2. ionic and H-bonds in tertiary structure can be altered by acids and akalis
    1. denatures enzymes
3. Concentrations
  1. Increasing Enzyme Conc
    1. Increases the frequency of successful collisions to form substrate-enzyme complexes
      1. This increases the rate of reaction
        Up to a point that the substrate runs out if substrate limited
      2. Increases the rate up to the point of "saturation"
        Saturation is when all the active sites are full
        Therefore adding more substrate makes no difference
        Conc of substrate does decrease over time as products formed
        Rate also decreases if substrate is not added, initial rate is the highest
  2. Increasing Substrate Conc
4. Inhibition
  1. Eznyme inhibitors prevent enzyme activity
    1. Molecules bind to enzyme to inhibit it
      1. Competitive
        Competitive inhibitors have similar shape to substrate
        Inihibtors and substrate compete to occupy active site
        If inhibitors occupy the active site no reaction takes place and the active site is blocked
        If there is high substrate conc, more chance for substrate to bind to active site
        Increases rate of reaction to a point
        Increase Inhibitor conc
        Inhibitors will occupy nearly all active sites leaving a very low rate of reaction
      2. Non-competitive
        Non-competitive inhibitor attach to binding sites, way from the active site
        Causes active site to change shape
        Substrate can no longer bind to active site
        Prevents enzyme from functioning
        Changing conc of substrate has no effect
Enzyme Reactions
1. Measuring the rate of enzyme-controlled reactions
  1. Measure how fast product is made
    1. Catalase breaks down hydrogen peroxide to form water and oxygen
      1. Measure how much oxygen produced
  2. Measure how fast substrate is broken down
Biological Catalysts
1. Catalysts for metabolic reactions
  1. Lower the Activation Energy of a Reaction
    1. If substrates are closer together, reduces repulsion easier to bond molecules together
      1. If breaking down molecule, attatching to active site puts pressure on molecules bonds
2. Have active sites and specific shape
  1. Proteins
    1. Highly specific due to tertiary structure
  2. Active site have complementary shape of substrate
    1. When substrate and enzyme react, substrate-enzyme formed

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Enzyme Inhibition (binary/octet-stream)

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	Created by Dominic Weston almost 7 years ago