Enzymes

Enzymes

1. Biological Catalysts

   • Speed up chemical reactions
     • Affecting structure as well as the function
     • Intracellular
       • Hydrogen Peroxide
         • toxic products kills cells
       • Catalase - inside cells break down the H2O2 to Water and Oxygen
     • Extracellular
       • Amylose & Trypsin workout outside the cell in the digestive system
         • Amylose found in saliva. It catalyses the hydrogen of starch into maltose.
         • Trypsin catalyses the peptide bonds into smaller polypeptides. Trypsin is produced in the pancreas and recreated in the small intestines.

2. Information about enzymes

   • Globular proteins
   • Contain active sites with a specific shape and bind to substate
     • Shape determine the enzymes tertiary structure.
     • Complementary to active sites

3. Activation energy

   • The energy needs before a reaction starts the normal heat
     • Enzymes reduce the activation energy allowing a reaction to happen a lower temperature it speeds up the rate of reaction
   • Substrates binding called enzymes substate complex

4. Lock and Key model

   • Substrates only fit in a complementary enzyme active site.

5. Induced fit

   • Substrates also changed shape

6. Factors affecting Enzymes Activity

   • Temperature
     • Rate of controlled reaction increasing when temperature increases
     • More kinetic energy - move faster
       • More collisions increases the chance of a reaction
         • Molecules vibrate more
     • Increasing the temperature too high denature the enzymes
   • pH
     • Enzymes have an optimum pH of 7
     • Above or below the optimum pH it can alter the ionic & H bonds
       • Therefore enzymes denature

7. Concentration

   • More enzymes molecules are more likely to collide and form an enzyme substrate concentration
   • Increase in concentration of enzymes increases + rate of reaction
     • Limited substrate means that enzyme will not have an effect any more
   • Substrate Concentration
     • Higher concentration faster reaction
       • More likely a collision will happen.
         • Only happens until a saturated point - after that it will have no effect
       • Concentration decreases over time therefore no other variables are changed= a reduced rate of reaction
       • Initial rate is the highest

8. Cofactors and coenzyme

   • Some enzymes require a non proteins substances - cofactors
     • Inorganic molecules
     • Helps enzymes to bind to substrate
     • not used up to changed in the reaction
   • Organic cofactors
     • Take part in the reaction
     • Know as coenzyme
     • acts as a carrier move chemical between enzymes
     • continually recycled
     • Vitamins

9. Inhibitors

   • Competitive Inhibitors
     • Similar shape with substrate
     • Bind to active site but no reaction takes place
     • Blocks active sites so no substrate fits
     • Higher concentration of inhibitors take more active sites
     • Increase concentration increase rate of reaction (up to a point )
   • Non- competitive inhibitors
     • Bind away from active site- allosteric site
     • Changes enzyme shape
     • Doesn't compete with substrate - they have different shapes
     • Increase in the substrate concentration doesn't have any affect
   • Reversible and Non reversible
     • Depends on the strength of their bonds
     • Strong Covalent - can't easily removed - irreversible
     • Weak hydrogen bonds or ionic bonds easily removed- reversible
   • Drugs and Metabolic Poisons Enzymes inhibitors
     • Medical drugs are inhibitors
       • Antiviral drugs - prevent viruses from replicating
       • Antibodies
         • Penicillin - inhibit proteins formation in cell walls , make cells burst as a result
     • Some are poisons
       • Cyanide
         • Irreversible reaction - respiration in cells die
       • Malonate
         • inhibits succinate dehydrogenase
       • Arsenic

10. Metabolic Pathway

    • Connected metabolic reactions
      • Lots of enzymes are inhibited by products
        • Product inhibition
          • final product in a metabolic reaction pathway
            • End product inhibitor.
              • Regulates pathway and controls how much product is being made.
              • Reversible
          • Reversible