Required Practical 3: Investigation of a factor affecting enzyme activity

Question 1

Apparatus diagram

Answer 1

Question 2

Source, substrate, and product of catalase

Answer 2

Source: potato, ginger, garlic, animal liver

Substrate: hydrogen peroxide

Product: Oxygen

Question 3

Possible independent variables

Answer 3

• Source of catalase
• Temperature
• Concentration of substrate
• Concentration of enzyme
• pH

Question 4

Possible dependent variables

Answer 4

• Number of oxygen bubbles produced
• Distance moved by meniscus in a connected glass tube
• Oxygen produced measured with a gas sensor
• Time taken for filter paper disc (soaked in enzyme) to rise to the surface of hydrogen peroxide solution

Question 5

Safety

Answer 5

• Enzymes must be stored at the appropriate temperature as stated by the manufacturer and safety guidelines.
• You should not use living tissues or cells, in accordance with the IB experimentation policy.
• Wear eye protection and gloves when handling the materials. Hands must be washed afterwards.

Question 6

Method

Answer 6

-Set up your apparatus, adhering to your safety precautions.

-Insert the catalase into the hydrogen peroxide.
Start the stopwatch, immediately.

• At 30-second intervals, measure the volume of oxygen in the measuring cylinder.
• Repeat steps 1–4 as many times as you have determined necessary, ensuring that all apparatus is suitably cleaned before each repeat and avoids contamination.
• Repeat steps 1–5 for as many concentrations of hydrogen peroxide as you have determined necessary for your experiment.

Question 7

Explain the effect of temperature on enzyme activity

Answer 7

• To convert substrate into products, enzymes collide with the substrate and bind to it at the active site.
• The reason the rate of reaction increases is due to the fact that an increase in temperature causes the number of collisions per unit of time to increase.
• The increase in temperature causes an increase in velocity and kinetic energy which is why the number of collisions increases.

Question 8

Explain how heat can denature enzymes

Answer 8

• Heat may also be converted into chemical potential energy.
• If the chemical potential energy increase is significant enough, some of the weak bonds that determine the enzymes’ shape will be broken.
• This is what leads to the denaturation of the enzyme.
• This means that too large of an increase in temperature will lead to a decrease in reaction rate due to the inactivity of the enzymes.

Question 9

What is an improvement to the investigation that would improve the precision of the results gathered?

Answer 9

Use a data logger to measure the volume of oxygen produced