To investigate and understand the rates of enzyme activity using five different concentrations of catalyse on a potato as an example.

GCSE Biology 29/04/2007

Biology Coursework

Investigating Catalyse Activity

Chris Weeks 10Y3

Aim

To investigate and understand the rates of enzyme activity using five different concentrations of catalyse on a potato as an example.

Research

In order to understand and carry out the investigation correctly, I have researched material appropriate to it.

Starch, proteins and fats are large, insoluble food molecules.
Even after the teeth have torn them, and the stomach has churned them, they are still too big and insoluble to pass through the blood stream.
They are broken down using enzymes.
Enzymes are specific, meaning they fit the substrate.
They are also catalysts and speed up the rate of reaction.
In digestion there are three important enzymes.

The building blocks are what the Food group are made up of.
Starch is broken down into glucose in the mouth and small intestine.
Proteins are broken down into amino acids in the stomach and small intestine.
Fats are broken down into fatty acids and Glycerol in the small intestine.
Most enzymes break substances down but some synthesize substances.
Enzymes are non-living.
They have an optimum pH and temperature.
Hydrogen peroxide will breakdown to oxygen and water in the presence of Catalyse.
The reaction will increase with the increasing enzyme concentration when molecules of hydrogen peroxide are more freely available.
However, when molecules of the substrate are in short supply, the increase in rate of reaction is limited and will have little effect.

Preliminary Work

After this research I can start to take information for my final experiment. To make my final experiment even better it is a good idea to do a preliminary experiment so I know my final experiment will display the right results.

My preliminary experiment was based on finding a range of values to use for my final experiment. I used the apparatus, which I will use in the final experiment. I cut up pieces of potato of the same volume and put them into different concentrations of catalyse. I wanted to see whether the concentration of the enzyme affected the reaction of the enzyme with the potato. My results from this preliminary experiment are shown in the table on the next page.

My results from this experiment have made me eliminate certain values from the proper experiment. For example, I can dispose of 0% as that is the same as putting potato in water meaning there is no reaction. I have also got rid of the 60-100% value, as it could prove dangerous towards me, as I will be doing the experiment with more potato. Because of this my new five-measurement range is 10%, 20%, 30%, 40%, and 50 %.

List of Variables

The following is a list of variables, which could be changed for the final experiment.

The temperature
The pH level.
The quantity of the substrate (H2O2).
The concentration of the substrate (H2O2).
Inhibition (Note below)

Inhibitors compete with the substrate for the active sites of the enzyme (competitive inhibitors) or attach themselves to the enzyme, altering the shape of the active site so that the substrate is unable to occupy it and the enzyme cannot function (non-competitive inhibitors).

Enzyme cofactors

Cofactors are none protein substances which influence the ...

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List of Variables

The following is a list of variables, which could be changed for the final experiment.

The temperature
The pH level.
The quantity of the substrate (H2O2).
The concentration of the substrate (H2O2).
Inhibition (Note below)

Inhibitors compete with the substrate for the active sites of the enzyme (competitive inhibitors) or attach themselves to the enzyme, altering the shape of the active site so that the substrate is unable to occupy it and the enzyme cannot function (non-competitive inhibitors).

Enzyme cofactors

Cofactors are none protein substances which influence the functioning of enzymes. They include activators that are essential for the activation of some enzymes. Coenzymes also influence the functioning of enzymes although are not bonded to the enzyme.

The concentration of the enzyme.

My chosen variable is the concentration of the substrate, which in this is hydrogen peroxide (H2O2).

I will make sure the temperature is equal for all tests by doing them all at room temperature.
I will keep the pH level of the substrate the same.
I will keep the quantity of hydrogen peroxide the same.
I cannot control the inhibition but it should not be a problem to the experiment.
Unless enzyme cofactors are present in the potato tissue containing the Catalyse, they will not be included in this investigation and therefore will not affect the rate of reaction and the results of this experiment.
I cannot keep the concentration or amount of enzyme the same, as different parts of the potato will have different amounts of enzyme in. The most I can do is to make the different pieces of potato the same volume.

Apparatus

The apparatus, which I will use in my final experiment, are:

A gas burette (as it is easier to record the results than with a boiling tube)
A conical glass (to put the potato and H2O2 in)
A bung and delivery tube
A bath of water (H2O)
A pair of Latex gloves (to wear whilst chopping the potato)
A digital stop clock (to time the experiment)
A potato (to use as the substance with the enzyme in)
A knife (to chop the potato into equal volumes)
A size 10 Borer (to help remove potato from the centre)
A ruler to help measure the pieces of potato so they are the same volume)
Five different quantities of H2O2.
Measuring cylinders (to measure the quantity of H2O2)
Test tube racks (to put the boiling tube in)
Sticky labels (so I can identify which concentration of H2O2 it is)

Diagram

Below there is a diagram of the equipment I will be using to conduct my experiment.

Safety Factors

To make sure no one is put into danger during the experiment, I am going to follow these safety factors.

I will wear latex gloves throughout the experiment.
I will wear goggles throughout the experiment.
Care will be taken whilst handling the chemicals as hydrogen peroxide is highly corrosive

Fair Test

To make sure this is a fair test I will keep these variables fixed:

The temperature

The pH level.
The quantity of the substrate (H2O2).
Enzyme cofactors
The concentration of the enzyme.
The quantity of the enzyme
The Inhibitors

On details on how I will keep these the same look at my “List of Variables” section.

Methodology

These bullet points are my method for the experiment.

Get out the equipment and set it out using the diagram showed earlier in the document.
Cut out ten different pieces of potato so they are the same shape and volume.
Put one of the five concentrations of H2O2 into the conical glass and put three discs of potato in.
Leave for three minutes.
The reaction will produce oxygen (O2), which shall travel through the delivery tube at the top of the conical glass.
The oxygen shall collect in the gas burette and cause the amount of water in the test tube to go down.
Record the amount of oxygen collected.
Repeat the experiment three times with each different concentration of H2O2.

Prediction

Using the information from my research and preliminary work I have made the following prediction. Hydrogen peroxide will breakdown to oxygen and water in the presence of Catalyse. This means the reaction will increase with the increasing enzyme concentration, as molecules of hydrogen peroxide are freely available. However, when molecules of the substrate are in short supply, the increase in rate of reaction is limited and will have little effect. Therefore the higher the concentration of H2O2, the greater the amount of oxygen given off, as there is a more violent reaction.

Results

On the following page I have displayed my results in the form of a table and graphs.

NOTE: On my first test for 30% concentration, the result was too far out from the others so I have done the test again. I will explain more later on.

Ranges of Results

Range between the different concentration’s average results

Over the page there are some graphs displaying these results.

This is the graph with the new average for 30% in. As you can see it is more or less the same shape apart from the line is steeper from 20% to 30% and less steep from 30% to 40%.

Analysis

In my prediction I said:

“The higher the concentration of H2O2, the greater the amount of oxygen given off, as there is a more violent reaction”

The results from my experiment have confirmed that this statement is true. In the gas burette it was clear that a reaction was taking place because of bubbles of oxygen gas being released and it was also creating a ‘fizzing´ in the boiling tubes.

You can see in the graph that the line goes upwards as it goes right, meaning there is a greater amount of oxygen being given off when the concentration is increased.

From the results in the first table, it is clear that some of them do not exactly fit. They are ‘anomalies’ or ‘outliers’. Although they are only slight errors, they are an indicator of possible errors in the practical. The most important error was the first result in testing with 30%. IT was quite a way off the others giving that group of results a range of 4.4. It is for this reason I decided to repeat that result. If I had more time I would have done all three again, but nevertheless second time round the result fitted in well with the others giving that group a range of 1.1cm.

If I had had more time, I would have also repeated the tests for both 40% and 50 %. This is because the range of results is above 2cm meaning they are slightly inaccurate. It would be better to repeat them or have a wider range of results (e.g. six) and then find the average, first eliminating any which are not in a 2cm range of the median result.

As you can see in both graphs, it is quite steep between 10%-20% and 40%-50%. Between 20%-40% however, the line is less steep, however it still goes up. This is because certain variables were not kept fixed, because I did not have access to certain equipment. For example, the amount of enzyme in the discs could vary as I could not check how much was contained in the potato beforehand and there were also times when the potato from which the discs was cut from was a different kind of potato. I have highlighted on this more in my evaluation.

Evaluation

In the whole the experiment could have been dramatically improved. Here are some things I could improve if I were to repeat this investigation.

Instead of using potato discs that have slight variations in size, and volume of catalyse, as a source for the enzyme, a specific concentration of the enzyme could have been put into a substance and then used. This way the reaction can be measured far more accurately reducing the chances of errors in the investigation.
In this experiment 5 enzyme concentrations were used. However, although there was a suitable range, it would be better to have a large range and to go as high as we can without putting ourselves into danger.
In this investigation we did three readings for each concentration so that an average rate of reaction for each enzyme concentration could be calculated. This could be improved by having a larger amount of readings thus reducing the chance of anomalies, once averaged.

In this experiment the test was done over three minutes. To get better and more accurate results it should be carried out over a greater time limit (e.g. 10 mins.).
As the experiment was carried out over five days, the temperature in the room was varied. This means the room temperature was not fixed. This could alter the rate of reaction. It is for this reason why that the experiment should be carried out in a room with fixed temperature.
Any change in pH affects the ionic and hydrogen bonding in an enzyme and so alters it shape. Each enzyme has an optimum pH at which its active site best fits the substrate. Variation either side of pH results in denaturation of the enzyme and a slower rate of reaction. In this experiment we did not have suitable equipment to check that the pH level was permanently the same. If we were to repeat the investigation the pH should be kept constantly at a pH level suited to the enzyme. This can be done using a pH7 buffer.

Many other experiments could evolve from this investigation. Some factors, which I would like to investigate, are:

The increase between two concentration averages in terms of oxygen released. This would be interesting to investigate if you had the correct equipment as you could see whether it the amount of oxygen released between two concentration averages goes up in a steady pattern. (E.g. 10%=7, 20%=10 so increase is of 3).
Whether the amount of enzyme affects the amount of oxygen released.
To use different food substances instead of potato to see whether this makes any change in the results.

From my experiment I do believe that I have enough results and understanding to complete my aim, which was:

“To investigate and understand the rates of enzyme activity using five different concentrations of catalyse on a potato as an example.”

I believe I have investigated the rates of enzyme activity well and got suitable results and understanding to confirm my prediction and draw a conclusion, which is:

“Hydrogen peroxide will breakdown into oxygen and water in the presence of Catalyse. The reaction will increase if the concentration of the enzyme is increased, as molecules of hydrogen peroxide are more freely available. However, when molecules of the substrate are in short supply, the increase in rate of reaction is limited and will not have a great effect. To summarize, the higher the concentration of H2O2, the greater the amount of oxygen given off, as there is a more violent reaction”

This piece of coursework was on investigating and understanding the rates of enzyme activity using catalyse as an example.

This has been written by Chris Weeks from 101A. Some information has been used from other people’s books and work so I have included a Bibliography.

I have used information from the following sources: