Lab Report

Effect of PH on enzyme activity

Objective

To investigate the effect of PH on the rate of activity of enzyme catalase

Introduction

The rate of enzyme activity relies on a number of factors. This includes temperature, substrate concentration, enzyme concentration, PH, and chemical inhibitors. Enzymes work differently in varying levels of temperature. Enzyme activity increases with increase in temperature up to a certain optimal point. After this point, the enzyme activity drops to zero. This is because of denaturing of enzymes when the temperature becomes so high (Bettelheim, 2010). Enzyme activity increases with increase in substrate concentration up to a certain optimal point. After the optimum, enzyme activity remains the same with enzyme concentration. This occurs because all the active sites of the enzyme would have been occupied making it unable to act on any additional substrate. Enzyme activity also increases with enzyme concentration. However, after a certain concentration level, the activity remains constant. Different enzymes work differently in different PH values (Seager & Slabaugh, 2011). Some enzymes work best in acidic conditions while others work best in alkaline conditions. Increasing the PH level will therefore affect enzyme activity differently depending on which PH environment the enzyme thrives best. Chemical inhibitors generally hinder enzyme activity. They do this by occupying the active sites of enzymes thereby preventing the enzymes from acting on the substrate.

Materials

· Hydrogen peroxide

· Catalase

· Buffers of varying PH levels

· Potassium permanganate

· Water

· 10 ml syringes

· Plastic cups

· Beakers

· 10 ml graduated cylinders

· Stop watch

· Sulfuric acid

Procedure

1. Label five 50 ml beakers with the PH level being tested

2. Add 10 ml of hydrogen solution to each beaker

3. Add 10 ml of the required buffer solution to the first beaker

4. Add to 10 ml of catalase to the first beaker to initiate reaction

5. Time the reaction for two minutes.

6. Stop the reaction by adding 10ml of sulfuric acid. Adding sulfuric acid denatures the enzyme stopping the reaction.

7. Measure the amount of hydrogen peroxide remaining in the beaker by adding drops of potassium permanganate from a syringe until a pinkish brown color is obtained. record the initial and final reading of the syringe

8. Repeat steps 3 to 8 for each of the PH level

9. Calculate the rate of reaction for each PH level by dividing the amount of hydrogen peroxide used by two minutes.

Control experiment

In the control experiment, the PH buffers were replaced with water and experiment repeated. In each case, instead of a PH buffer, water was added and rate of reaction determined.

Results

Potassium permanganate	PH level	PH level	PH level	PH level	PH level	PH level	PH level	PH level
	11	10	9	8	7	6	5	3
Final reading	0ml	2.2ml	2.8ml	3.5ml	4ml	3.6ml	3.0ml	2.1ml
Initial reading	8ml	8ml	8ml	8ml	8ml	8ml	8ml	8ml
Amount of KMnO4 used	8ml	5.8ml	5.2ml	4.5	4ml	4.4ml	5ml	5.9ml
Amount of H2O2 used	0	1.2ml	1.8ml	2.5ml	3ml	2.6ml	2ml	1.1ml

PH level	11	10	9	8	7	6	5	3
Rate of reaction (ml/min)	0	0.6	0.9	1.25	1.5	1.3	1	0.55

Discussion

From the results, it can be seen that PH affects the rate of activity of enzyme catalase. The results obtained indicate that catalase in neutral conditions. This can be seen by its high rate of reaction at the PH value of 7. The enzyme activity reduces as PH increases. At PH value of 11, there is no enzyme activity. At PH value of 11, catalase is denatured making it unable to act on the hydrogen peroxide (Illanes, 2008). The enzyme activity also reduces when the PH reduces. At PH value of 6, the rate of reaction reduces to 1.3ml/minute. This reduces to up to 0.55ml/minute at the PH value of 3. The results from the experiment provide crucial insight into how enzyme catalase can be maximized during reactions. They show that catalase can be utilized effectively is the PH value is set at 7.

The control experiment was used to prove that PH affects the rate of reaction of catalase. For the control experiment, the rate of reaction was constant for all settings. This shows that PH has an effect on how catalase acts on substrates (Seager & Slabaugh, 2011). This experiment was in line with the established academic facts concerning factors that affect enzyme activity. It proved that PH is one of the factors which determine how an enzymes act on enzymes.

Sources of errors

One source of errors was the use of potassium permanganate. It was possible that the potassium permanganate used to determine the remaining hydrogen peroxide was higher or lower than what was actually required. Another source of error was the enzyme and substrate concentration. The settings could have had varying concentrations of these two factors and since they also affect the rate of reaction, this could have affected the rate of reaction in some experimental settings. However, despite the possible errors, the experiment was generally successful in determining the effect of PH on enzyme activity.

Conclusion

Generally, catalase works better in neutral conditions as compared to acidic or alkaline conditions.

References

Bettelheim, F. A. (2010). Introduction to general, organic, and biochemistry. Belmont, CA: Thomson Brooks/Cole.

Illanes, A. (2008). Enzyme biocatalysis: Principles and applications. New York: Springer.

Seager, S. L., & Slabaugh, M. R. (2011). Organic and biochemistry for today. Australia: Brooks/Cole Cengage Learning.