ap bio unit 3 - enzymes

Enzymes

  • Used as catalysts in chemical reactions

  • Are proteins

  • Shape determines function

  • Each enzyme only works on one substrate

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  • Enzymes are NOT used up in reactions

  • Tertiary structure is what is most important for enzyme function

  • Work by lowering the activation energy required for the reaction to begin

    • In living systems body temp provides energy needed for reactions to begin

      • Enzymes allow reactions to happen at body temperature that normally could not

    • Enzymes do not change the amount of reactants or products in a reaction

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  • Activation energy is lowered by changing the shape of the substrate in the active site


  • Reaction Types

    • Endergonic and anabolic reactions absorb/require energy

    • Exergonic and catabolic release energy

    • Energy released from exergonic reactions power endergonic reactions

    • Redox reactions are how energy is moved

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  • Optimum Conditions

    • Reaction rate can be measured by how quickly product is being made or reactants are being used up

    • Higher substrate concentration=faster reaction rate to a point

      • At some point all enzymes are being used at all times so reaction rate cannot increase

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  • Higher enzyme concentration= faster reaction- more enzymes mean more product can be made

  • Enzymes only work in a particular pH and temperature range

    • Outside of this range enzymes denature and stop working altogether

      • Caused by shape changes do to changes in bond interactions

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  • Inhibitors

    • Change reaction rates of enzymes

    • Two types

      • Competitive inhibitors

        • Temporarily bind to active site preventing substrate from binding

        • Shaped similarly to substrate

        • Can be reversed by increasing substrate concentration

      • Noncompetitive inhibitors

        • Bind to an allosteric site

          • Allosteric sites are anywhere on the enzyme other than the active site

        • Effectively turn off the enzyme 

        • Increase in enzyme concentration can reverse effect