IA on effect of diff pH (1,4,5,7,9) on the rate of decomposition of H2O2 measured using a pressure sensor.

1. Centrifuge to spin down the extract Catalase extract (clear solution used) Yeast, pressure sensor, H2O2
Diff pH used (1,4,,5,7,9) to investigate the optimum condition for enzyme catalase
Catalase extracted from yeast cell.
5% (v/v) H2O2 used.
Pressure sensor to measure O2 released.
Reaction mechanism
Procedure:
5g of yeast powder added to 50ml water (10%) – centrifuge to collect extract
1ml catalase extract added to 1 ml of buffer of diff pH. Incubate at RT for 5 mins.
Solution mix added to 5ml of 5% H2O2
Rate was measured – change of pressure over time.
Hydrogen peroxide decomposition – O2 production
2H2O2→ 2H2O + O2
Effect of diff pH (1,4,5,7,9) on the rate of decomposition of H2O2 measured using a pressure sensor.

2. pH Rate/kPas-1
1 0.3184
4 2.859
5 2.609
7 2.747
9 2.876
-ve control 0.01430
Rate measured as pressure change over time (45s).
Lower rate using yeast extract after centrifuge
Higher rate using yeast solution
Effect of diff pH (1,4,5,7,9) on the rate of decomposition of H2O2 measured using a pressure sensor.
Lower rate using yeast
extract after centrifuge
Negative control - only pH
Using yeast solution
pH Rate/kPas-1
1 0.003852
4 0.07138
5 0.08175
7 0.1067
9 0.09681
-ve control 0.01430
Using yeast extract

3. Rate measured as pressure change over time (45s).
Lower rate using yeast extract after centrifuge
Effect of diff pH (1,4,5,7,9) on the rate of decomposition of H2O2 measured using a pressure sensor.
pH Rate/kPas-1
1 0.003852
4 0.07138
5 0.08175
7 0.1067
9 0.09681
-ve control 0.01430
Using yeast extract
0
0.02
0.04
0.06
0.08
0.1
0.12
0 2 4 6 8 10
Rate
of
decomposition
pH
pH vs Rate of decomposition
Rate decomposition optimum at pH 7
but still works at alkaline medium at pH 9
pH 1 – enzyme denatured and precipitation was seen

4. Method 1 Method 2
Time Time
Volume Pressure
• Rate = Δ vol O2 over time
• Volume recorded
• Rate = Δ pressure O2 over time
• Pressure recorded
Procedure
2H2O2 → O2 + 2H2O
Rxn: H2O2 with diff (catalyst) measured using TWO diff methods
• 2H2O2 → O2 + 2H2O
(H2O2 limiting, KI excess)
• Pipette 1ml 1.0M KI to 20ml of 1.5% H2O2
• Vol O2 released recorded at 1 min interval
• Repeated using 3% H2O2 conc
Time/m Vol O2
(H2O2 1.5%)
Vol O2
(H2O2 3.0%)
0 0.0 0.0
1 8.5 14.0
2 15.0 26.5
3 21.0 34.0
4 26.0 39.0
Volume O2
Time
3 %
1.5 %
Effect of diff pH (1,4,5,7,9) on the rate of decomposition of H2O2 measured using a pressure sensor.

5. • 2H2O2 → O2 + 2H2O
(H2O2 limiting, KI excess)
• Pipette 1ml 1.0M KI to 20ml of 1.5% H2O2
• Pressure O2 released recorded at 1 min interval
• Repeat using 3% H2O2 conc
Method 1 Method 2
Time Time
Volume Pressure
• Rate = Δ vol O2 over time
• Volume recorded
• Rate = Δ pressure O2 over time
• Pressure recorded
Procedure
2H2O2 → O2 + 2H2O
Time
3 %
1.5 %
Time/m Pressure O2
(H2O2 1.5%)
Pressure O2
(H2O2 3%)
0 101.3 101.3
1 102.4 103.4
2 103.5 105.6
3 110.3 115.2
4 113.5 118.2
Pressure O2
Rxn: H2O2 with diff (catalyst) measured using TWO diff methods
Effect of diff pH (1,4,5,7,9) on the rate of decomposition of H2O2 measured using a pressure sensor.