07. Investigation into the effect of temperature or pH on enzyme activity

  • 00:23 Why is sodium carbonate solution added to the lipase solution?
  • 00:51 What is the colour of the indicator at the start?
  • 00:55 Which molecules in the milk are hydrolysed by lipase?
  • 00:57 Which products of this hydrolysis reaction cause the colour change of the phenolphthalein?
  • 00:58 What is the effect of temperature on the activity of lipase enzyme?
  • How could you amend this experiment to find out how pH affects enzyme activity?
  • milk, full-fat or semi-skimmed

  • phenolphthalein in a dropper bottle

  • lipase solution (5g/100cm3)

  • Sodium carbonate solution (0.05 mol dm–3)

  • 5 x test tubes and rack

  • 2 x 10cm3 syringes / measuring cylinders

  • 2cm3 syringe

  • stirring rod

  • thermometer

  • water baths set to 15oC, 25oC, 35oC, 45oC and 55oC

Hazard Risk Control measure


Enzymes may produce allergic reactions. They can cause asthma and irritate the eyes, nose and skin

Use the smallest amount possible. Wear eye protection. Wash hands thoroughly after use.

Phenolphthalein indicator – irritant to eyes and skin, acute toxicity

Contact with eyes and skin.


Poisonous if swallowed

Eye : flood with tap water (10min)

Skin: drench with water (10min)

Do not drink Wash hands thoroughly after use