required practical 1 - enzyme controlled reaction

• what is the method of this practical?

  1. take 2 flat bottomed tubes and add 5cm3 of milk to each tube & add 5cm3 of distilled water to one tube & add 5cm3 of HCL to the other
  2. take 3 test tubes & measure 5cm3 milk into each then place in a water bath at 10 degrees for 5 minutes
  3. add 5cm3 trypsin to each tube then start the timer
  4. record the time it takes for milk samples to completely hydrolyse & become colourless
  5. repeat steps 2-3 at temperatures of 20, 30, 40 & 50
• why is distilled water added to one test tube?

  it indicates the absence of enzyme activity
• why is hydrochloric acid added to the other test tube?

  indicates the colour of a completely hydrolysed sample
• what is the conclusion of this practical?

  • milk contains a protein called casein which is hydrolysed by trypsin, a protease enzyme, to cause the milk to become colourless
  • as temperature increases, kinetic energy increases so more enzyme-substrate complexes form, so rate of reaction increases
  • as temperature increases past optimum temperature, bonds in the tertiary structure of the enzyme break, which changes the shape of the active site so substrate & enzyme are no longer complementary