Enzymes

Enzymes

1. Active sites and enzymes

   • Enzymes = globular proteins; biological catalysts
   • Substrates = substances enzymes convert into products
   • produced by living organisms
   • enzyme substrate specifity = must match
   • active site = special region on surface of enzyme that substrate binds to
   • only matching shapes can bind
   • once substrate converted to product, released

2. Enzyme activity

   • molecular motion; collision of sub. with act. site
   • stages
     • sub. binds to act. site
     • change into products
     • products separate from site
   • most reactions, substrates dissolved in water
   • collisions due to random movement
   • successful only if aligned correctly

3. Factors affecting enzyme activity

   • Temperature
     • Liquid temp increases, enzyme activity increases
     • enzyme heated; denatures - zero activity
   • substrate concentration
     • more substrate = more successful collision = more activity
     • goes down after a point
   • pH
     • acidity and alkalinity
     • lower pH, higher H ion conc
     • 1 unit = 10x acidity
     • pH 7 neutral
     • optimum pH = highest activity
     • denatured when H ion conc too high/low
     • wide range of optimum

4. Denaturation

   • structure permanently altered
   • unsuitable temperature or pH

5. Immobilised enzymes

   • widely used
   • discovered 1897 Buchner brothers
   • clearer falsification of vitalism
   • more than 500 commercial uses
   • limits enzyme movement
   • advantages
     • can be removed easily; stop reaction and avoid contamination
     • cost saving as recyclable
     • increases stability and decreases degradation
     • substrates can be exposed to higher enzyme conc. = higher reaction rates