AQA Required Practical- Enzyme Activity

Substrate Details


  • Makes up 20-45% proteins found human breast milk 
  • is Phosphoprotein, meaning that it has a phosphate group modified to/ bonded to its residue group
  • is polar molecule: MAINLY HYDROPHOBIC/ forms Micelle's in presence of water (similar to emulsion) = why milk colour/ texture is cloudy/ thick
  • globular protein when hydrolysed breaks down into AMINO ACIDS, CARBOHYDRATES, CALCIUM/ PHOSPHORUS
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Trypsin Details


  • naturally occuring "Organic" enzyme/ secreted by PANCREAS to break down long polyprotein chains= smaller molecules/ peptide chains= absorped more easily by EPITHELIAL lining of SMALL INTENSTINE= blood stream 
  • Optimum temperature= 37 degrees C
  • Protease= specific only to proteins
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Effect of Temperature on Rate of Reaction

1. Kinetic Energy of REACTING MOLECULES increases

  • more collisions with greater force= greater chance of physical interaction between enzyme's active site + substrate

2. Rate of reaction increases


3. Rate of reaction peaks at optimum point of between 35-40 degrees C

  • all active sites catalysing break down casein ("in use")- increase of temperature/ no effect on enzyme activity

4. weaker hydrogen and ionic bonds between residue groups in tertiary structure of enzyme under strain/ alters the 3d shape of enzyme

  • substrate lesser chance of binding with active site/ rate of reaction decreases as process takes longer length of time

5. Enzyme denatures as 3d structure collapses

  • vibrational energy too great/ intense and bonds between residue groups break, the active site's shape is no longer specific to substrate shape/ pernamently alterd/ unable to function/ no ES- COMPLEXES formed
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