The effects of surrounding conditions on enzyme activity

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  • The effects of surrounding conditions on enzyme activity
    • Enzyme concentration
      • The higher the enzyme concentration the greater the rate of reaction until substrate becomes the limiting factor
      • An enzyme is converted into its active form, increasing its concentrationwhen the product it makes is needed
      • When the product is no longer needed, the enzyme is deactivated, lowering its concentration again
      • Self-regulating mechanism
    • Substrate concentration
      • The more substrate there is, the faster the enzyme will work until all the active sites are full all the time
      • After that, no matter what the substrate concentrationis, the reaction will not go any faster
      • All enzymes have a maximum rate at which they can work
    • Competitive and non-competitive inhibitors
      • Competitive inhibitors
        • Similar in shape to the substrate
        • Fit into active site but cannot be converted into the product
        • The more competitive inhibitors there are, the less chance there is of a successful collision between enzyme and substrate
      • Non-competitive inhibitors
        • These bind to the enzyme away from the active site, but alter the shape of the enzyme so the substrate cannot fit into the active site
        • They switch off enzymes
        • If the  inhibitor is removed, the enzyme functions as normal
    • pH
      • Measure of acidity (scale of 1 - 14)
        • pH 7 is neutral
        • pH lower than 7 is acidic, lot of H+ ions
        • pH higher than 7 is basic, more OH- ions
      • Every enzyme has an optimum pH
        • Stomach enzymes work best around pH 2
        • Small intestine enzymes work best around pH 8
        • Intracellular enzymes have an optimum around neutral
      • Away from the optimum pH, the H+ and OH- ions neutralise the charges so the enzyme and substrate are no longer complementary
        • Extremes of pH can denature enzymes
    • Temperature
      • As temperature increases, the rate of reaction increases as the molecules are moving faster and there is more chance of collision
      • When temperatures get too high, the enzymes vibrate more vigorously, causing the weaker bonds (e.g. hydrogen bonds) to break
      • After the optimum temperature (around 37C), the enzyme is denatured and this process is permanent

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