Q9 Enzymes

Question 1

Investigate the effect of pH on the rate of enzyme activity — Method

Answer 1

1. Add catalase, pH9 buffer and washing up liquid to a graduated cylinder.
2. Add Hydrogen peroxide to a boiling tube.
3. Place the boiling tube and graduated cylinder in a water bath of 25°C.
4. Wait for both to reach 25°C.
5. SLOWLY add the hydrogen peroxide down the side of the graduated cylinder.
6. Calculate the height of oxygen & water (foam – rate of enzyme activity).
7. Record the initial volume and then final volume, after two minutes.
8. Repeat this using pH 4, 7, and 10.

Question 2

Investigate the effect of pH on the rate of enzyme activity — Expected Result

Answer 2

pH 9 was the optimum pH for the enzyme catalase, as it produced the most product.

Question 3

Investigate the effect of temperature on the rate of enzyme activity — Method

Answer 3

1. Add catalase, pH9 and washing up liquid to a graduated cylinder.
2. Add Hydrogen peroxide to a boiling tube.
3. Stand the graduated cylinder and boiling tube of H₂O₂ in a water bath at 0°.
4. SLOWLY add ice cold hydrogen peroxide down the side of the graduated cylinder.
5. Calculate the height of oxygen & water (foam – rate of enzyme activity). (Initial volume)
6. Record the initial volume and then final volume, after two minutes.
7. Repeat the procedure for different temperatures of 25°C, 40°C and 60°C.
8. Record results.

Question 4

Investigate the effect of temperature on the rate of enzyme activity — Expected Result

Answer 4

25°C was the optimum temperature for the enzyme catalase, as it produced the most products: oxygen and water visible as foam.

Question 5

Investigate the effect of heat denaturation on the activity of an enzyme — Method

Answer 5

1. Blend celery with water and filter to extract catalase. Place the catalase in a boiling tube and place in a water bath at 100°C.
2. Add the boiled catalase, pH9 and washing up liquid to a graduated cylinder.
3. Stand the graduated cylinder and boiling tube of H₂O₂ in a water bath at 25°C.
4. SLOWLY add hydrogen peroxide down the side of the graduated cylinder.
5. Calculate the height of oxygen & water (foam – rate of enzyme activity).
6. Record the initial volume and then final volume, after two minutes.
7. Repeat the procedure with unboiled catalase. CONTROL.
8. Record results.

Question 6

What is the chemical nature of enzymes

Answer 6

Protein

Question 7

What is the enzyme, its source, the substrate, products, control

Answer 7

Enzyme: catalase
Source: celery
Substrate: hydrogen peroxide (H2O2)
Products: water and oxygen which are visible as foam
Control: boiled catalase (except heat denaturation its Unboiled)

Question 8

What is the purpose of washing up liquid

Answer 8

Trap the oxygen being released which helps form the foam

Question 9

In PH experiment why is hydrogen peroxide put in water bath

Answer 9

It has come from fridge and needs to be brought up to optimum temperature so that doesn’t affect the PH’s effect on the rate of activity

Question 10

How do you calculate enzyme rate of activity

Answer 10

Final volume - initial volume after 2 minutes
Volume of foam per minute

Question 11

PH and temperature/ denaturation experiment: factors kept constant

Answer 11

• Temperature through set water bath at 25 degrees Celsius (PH and denaturation)
• Substrate - same volume and concentration of hydrogen peroxide
• enzyme concentration - same volume of enzyme
• PH - using PH buffer 9 (temp and denaturation)

Question 12

How do temperature and PH graphs vary

Answer 12

PH graph is very narrow whereas temperature range is much rounder but they are both n shaped

Question 13

What is the control in the heat denaturation experiment

Answer 13

Unboiled catalase

Question 14

What is denaturation

Answer 14

The enzymes active site has permanently lost its shape and loses its function

Question 15

Result of heat denaturation

Answer 15

Boiled catalase produces no foam (no oxygen and water)
Unboiled produces oxygen and water visible as foam

Question 16

How did you denature enzymes

Answer 16

Place the catalase in a boiling tube and place in a water bath at 100°C