Effect of Ph on Enzyme Activity

Aim: To investigate the effect of PH on the activity of the enzyme catalase
Hypothesis: The enzyme’s optimum PH will be 7.5 as 7.5 is basic.
Background information:
Changes in pH may not only affect the shape of an enzyme but it may also change the shape or change properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis. Extremes in pH can denature enzymes.
Catalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it functions to catalyse the decomposition of hydrogen peroxide to water and oxygen. Catalase is made up of four polypeptide chains. The optimum pH for human catalase is approximately 7. In geneal enzyme have a pH optimum. However the optimum is not the same for each enzyme.

• Sodium phosphate buffer solutions of ph 4.4,5.2,6.5,7.5,9
• Hydrogen peroxide solution
• Potato
• Measuring cylinder 10ml and 100ml
• Stop watch
• Retort stand and clamp
• Trough
• Cork borer
• Test tube
• Rubber stopper
• Delivery tube
• Scalpel
Risk assessment
Risk Safety
Hydrogen peroxide is a corrosive solution and can cause burns to the skin Wear hand gloves to protect hands and safety glasses to protect eyes
Buffer solution of ph 4.4,5.2,6.5 are acidic therefore cause burn to skin Wear hand globes to protect hands and safety glasses to protect eyes
Scalpel is sharp and can cause cuts Must be kept at the centre of the bench when not in use and should be pointing face downwards when passed around.

1. Students set up the apparatus as shown below

2. Students used a cork borer to cut 5cm long potato cylinders and use a scalpel to cut it into ten ½ cm lengths. Students placed it in the test tube.
3. Students added 4ml of ph 4.4 buffer solution and recorded the ph. Students added 5ml of H202 to the test tube and immediately inserted a rubber stopper and then started the stop watch.
4. Students recorded...