Practical skills

• How do we investigate the effect of a named variable on the rate of an enzyme controlled reaction? - Control samples

  1. Make two control samples:
  2. Add 5cm^3 of powdered milk suspension to 2 flat bottomed tubes.
  3. Add 5cm^3 of distilled water to one tube (to indicate the absence of enzyme activity)
  4. Add 5cm^3 of hydrochloric acid to another tube (to indicate the colour of a completely hydrolysed sample)
• How do we investigate the effect of a named variable on the rate of an enzyme-controlled reaction? - Experimental samples

  1. Take 3 test tubes and measure 5cm^3 of milk into each. Place in water bath at 10 degrees Celsius for 5 minutes to equilibrate.
  2. Add 5cm^3 trypsin to each test tube simultaneously and start the timer immediately.
  3. Record how long it takes to completely hydrolyse and become colourless.
  4. Repeat steps 2-3 at different variables
  5. Find the mean time for the milk to be hydrolysed at each (variable) and use this to work out the rate of reaction
• How do we work out the rate of reaction?

  1 / mean time
• What are the 4 named variables in RP 1 (enzyme practical)?

  Temperature

  pH

  Substrate concentration

  Enzyme concentration