06 Enzymes


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06 Enzymes

  1. 1. ENZYMES
  2. 2. Enzymes <ul><li>Most, but not all end in the suffix …ase </li></ul><ul><li>Participate in reactions but are not used up or changed in any way </li></ul><ul><li>… although they can eventually “wear out” </li></ul><ul><li>Can perform either catabolic (destructive) reactions. eg. 1 substrate = 2 products </li></ul><ul><li>Can perform either anabolic (constructive) reactions. eg. 2 substrate = 1 products </li></ul>
  3. 3. Some quick facts. Enzymes … <ul><li>Act at both the intra and extracellular level </li></ul><ul><li>Act on SUBSTRATE and yield PRODUCT </li></ul><ul><li>Reduce the ACTIVATION energy required to start a reaction in the body </li></ul><ul><li>Are very specific, each individual type of substrate is acted upon by a specific enzyme </li></ul><ul><li>Generally names are based on the specific substrate (eg lipids acted upon by lipase) </li></ul>
  4. 4. Enzyme Structure <ul><li>Enzymes have an active site and a regulatory region </li></ul><ul><li>The active site is where substrate binds to the enzyme </li></ul><ul><li>The regulatory region is where cofactors coenzymes or enzyme inhibitors can alter the function of an enzyme </li></ul>Substrate Active site Regulatory region Products Enzyme inhibitor
  5. 5. Enzymes – inhibitors / cofactors <ul><li>Enzyme inhibitors can be either competitive or non-competitive </li></ul><ul><li>A competitive inhibitor blocks the substrate from entering the active site </li></ul><ul><li>A non-competitive inhibitor binds to the regulatory region, thereby changing the shape of the active site </li></ul><ul><li>Other enzymes will not work unless a particular cofactor occupies the regulatory region </li></ul>
  6. 6. The “Lock and Key” model of enzyme activity <ul><li>The enzyme provides a perfect fit for a particular substrate </li></ul>
  7. 7. The “Induced Fit” model of enzyme activity <ul><li>The substrate induces the enzyme to change shape to create a tighter fit </li></ul>
  8. 8. Factors Affecting Enzyme Activity <ul><li>pH </li></ul><ul><li>Most biological enzymes operate at a neutral pH range of 6-8 </li></ul><ul><li>If enzymes are at a pH outside their optimum range, their shape will change and they will be less efficient. </li></ul>Enzyme Cells Carbonic Anhydrase Trypsin Pepsin Location Blood Small Intestine Stomach Opt. pH 7.6 7.4 8.0 2.0
  9. 9. Factors Affecting Enzyme Activity <ul><li>Temperature </li></ul><ul><li>Most biological enzymes have an optimum temperature of 37° </li></ul><ul><li>If an enzyme is exposed to temperatures higher than optimum, it will permanently denature. </li></ul><ul><li>If an enzyme is exposed to temperatures lower than optimum, it will become inactive until temperature returns to optimum. </li></ul><ul><li>The enzymes of other organisms have optimum temperatures suited to the environment in which they live </li></ul>
  10. 10. Effect of temperature
  11. 11. Factors Affecting Enzyme Activity <ul><li>Enzyme Concentration </li></ul><ul><li>An increase in enzyme conc. will cause an increase in reaction rate but won’t increase the yield. </li></ul><ul><li>Substrate concentration </li></ul><ul><li>Reaction rate will initially increase as unoccupied enzymes take on substrate but will then plateau. </li></ul><ul><li>Inhibition </li></ul><ul><li>Other molecules can block the active site or regulatory region of an enzyme. </li></ul>
  12. 12. Increasing substrate concentration
  13. 13. Enzymes – advanced content <ul><li>Biochemical pathways </li></ul><ul><li>Inhibition of biochemical pathways </li></ul><ul><li>Allosteric enzymes </li></ul><ul><li>Biochemical processes </li></ul>