Investigating the effect of pH on catalase activity

In a nutshell

There are several factors that affect the activity of enzymes. Catalase is an enzyme that breaks down hydrogen peroxide into water and oxygen. By using catalase to break down hydrogen peroxide at different temperatures, you will be able to investigate the effect of temperature on enzyme activity.

Equations

The first equation is the word and symbol equation of the breakdown of hydrogen peroxide. The second equation can be used to calculate the rate of reaction after the experiment.

WORD EQUATION	symbol equation
$hydrogen\space peroxide \rightarrow water + oxygen$	$2H_2O_2 \rightarrow 2H_2O + O_2$
$mean\space rate \space of \space reaction = {mean \space volume \space of \space oxygen \over time \space taken}$	$R = {V\over t}$

Variable definitions

QUANTITY NAME	syMbol	UNIT NAME	UNIT
$rate$	$R$	$volume \space per \space time$	$cm^3/s$
$volume$	$V$	$centimetre \space cubed$	$cm^3$
$time$	$t$	$second$	$s$

Equipment list

The following equipment list can be used to conduct an experiment to evaluate the effect of temperature on enzyme activity.

EQUIPMENT	USE
Water bath	To control the temperature of the boiling tubes.
Source of catalase (e.g., potato)	The enzyme that will be used in this practical.
Hydrogen peroxide solution	The chemical that will be broken down in this practical.
Measuring cylinder	To measure the amount of oxygen produced.
Delivery tube	To connect the test tube to the measuring cylinder and prevent oxygen from escaping.
Pipette	To put the correct amount of hydrogen peroxide into the boiling tubes.
Stopwatch	To measure the time.
Thermometer	To measure the temperature.

Experiment 1: Investigating the effect of temperature on the rate of reaction of catalase enzyme

Experimental variables

The independent variable is the one you change. The dependent variable is the one that depends on what has been changed, therefore it is the one that is measured. The constant variable is one that has been kept constant.

Independent variable	$The\ temperature\ of\ the\ water\ bath.$
Dependent variable	$The\ volume\ of\ oxygen\ produced.$
Control variable	$The\ size\ of\ the\ potato\ pieces\ and\ amount\ of\ hydrogen\ peroxide.$

Safety precautions

When carrying out experiments, it is essential to consider safety precautions. This is so you and others do not get hurt.

HAZARD	RISK	SAFETY MEASURE
Hydrogen peroxide	Hydrogen peroxide can cause irritation to the eyes and skin.	Make sure to wear eye protection and gloves when handling hydrogen peroxide.

Method

This is your instructions on how to complete the experiment.

Biology; Biology practicals; KS4 Year 10; Investigating the effect of pH on catalase activity

1.	Bung
2.	Conical flask
3.	Potato cubes
4.	Hydrogen peroxide
5.	Delivery tube
6.	Volume of water displaced by oxygen
7.	Water bath

1.	Add a set amount of hydrogen peroxide to a boiling tube using a pipette. Then, put the tube into the water bath at $10\degree C$ .
2.	Set up the equipment as illustrated in the diagram above.
3.	Add a cube of potato to the test tube and attach the bung to the tube as quickly as you can. Start the timer on the stopwatch.
4.	After one minute has passed, measure how much oxygen has been produced. Record this value and repeat the test three times.
5.	Repeat steps 1-4. Each time, increase the temperature of the water bath (e.g. $20\degree C,\space 30 \degree C,\space 40 \degree C$ ). Remember to record all the values in a table.

Analysis

This is how you can use your data to be able to form conclusions.

1.	You will now have a table with a list of temperatures and the volume of oxygen produced by the hydrogen peroxide in a minute.
2.	Calculate the mean volume of oxygen produced at each temperature. $mean\space volume = {volume\space 1 \space + \space volume\space 2 \space + \space volume\space 3 \over 3}$
3.	Then, calculate the mean rate of reaction at each temperature. $mean\space rate \space of \space reaction = {mean \space volume \space of \space oxygen \over time \space taken}$
4.	You should then plot the rate and the temperature onto a graph. The mean rate of reaction should be on the $y$ -axis as it is based on the dependent variable. The temperature of the solution should be on the $x$ -axis as it is the independent variable. Draw a line through the points on the graph.

Conclusion

Your graph should show the optimum temperature for catalase enzyme activity. At this temperature, the greatest volume of oxygen will have been produced due to the breakdown of hydrogen peroxide. This is because the enzyme will be the most efficient at this temperature. There will be a gradual loss of enzyme activity away from the optimum temperature, as the active site will become distorted. The graph will also show that, at extreme temperature values furthest from the optimum temperature, there will be no rate of reaction. This is because the catalase enzyme will be completely denatured at these temperatures and be inactive. The shape of the graph should be similar to the graph below.

Biology; Biology practicals; KS4 Year 10; Investigating the effect of pH on catalase activity — 1. Temperature is too low so enzymes do not have enough energy to react, 2. Temperature is too high so enzymes denature.

Evaluation

Once you have completed your experiment, it will be important to consider the quality of your data and how accurate your results are. Identify potential sources of random or systematic error and suggest possible improvements and further investigations.