In lessons I am researching into enzymes and their functions, also what affects them. The basis of this investigation is to find out what affects the rate of reaction while using enzymes. In the experiment I am testing whether the concentration of the acid (hydrogen peroxide) affects the amount of reaction and if any in what way.

I will conduct this experiment by testing the differences in the amount of reaction in a minute. The reaction will be made by reacting catalyse (found in potatoes, which I’ll cut up), and hydrogen peroxide. To change the concentration I will dilute the hydrogen peroxide in steps using water. I will measure the amount of gas given off (measured in bubbles) in a minute.

Background Information

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The chemical equation for this experiment is:

Hydrogen peroxide catalyse water + oxygen


Enzymes are basically catalyst with their own uniqueness. Unlike other catalysts they have a very delicate structure, this makes them venerable to become denatured if exposed to high temperatures. Denatured is when the enzymes stops functioning, this does not mean it is dead as it was never alive.

Enzymes are classified into categories, these are; hydrolytic, oxidizing, and reducing enzymes. Their name depends on the type of reaction they control.

Hydrolytic enzymes accelerate reactions when substances are broken down into simpler compounds through reaction with water.

Oxidizing enzymes, known as oxidases, accelerate oxidation reactions. Reducing enzymes speed up reduction reactions, in which oxygen is removed.

There are many other enzymes, which catalyze other types of reactions.

Researching on enzymes I have found what affects them while reacting, they include:

* Temperature

* Concentration of the Enzyme

* The Ph

* Concentration of Substrate

I have researched into how temperature affects the amount of reaction. I found that every enzyme has it pinnacle temperature of reaction and then it starts to denature. Also the solution starts to become unstable. While leading up to that maximum temperature the amount of reaction continues to grow. As the temperature heats up the molecules move about more and the chance of collision with another enzyme is greater. This called the Collision Theory.

Concentration of the Enzyme affects the amount of reaction because the chance of collision is higher when there the enzyme is more concentrated as there is more of it.

The concentration of substrate affects the chance of reaction just like the concentration of the Enzyme.

The Ph affects the reaction because it must only be at a certain ph.

I have done work with amylase (an enzyme produced in the mouth) and found that these particular enzymes convert starch into sugar. With that particular experiment I found out how long it takes for an enzyme to react.

Hydrogen Peroxide

This is a chemical compound of Hydrogen and Oxygen. Its chemical formula is H2O2. It is a colourless, syrupy liquid. It can blister skin and can blind the eyes. It solidifies at -0.41 degrees Celsius. Concentrated solutions are unstable and can blow at a temperature of 100 degrees Celsius. It is kept in a darkened container to avoid contact with light, which could lead to an explosion. For commercial uses it is concentrated at 3 or 30 percent.

It is used medicinally, in the form of a 3 per cent aqueous solution. It is used as an antiseptic and throat wash. Hydrogen peroxide is used in restoring the original colours to paintings that have darkened through the conversion of the white lead used in the paintings to lead sulphide. It is also used as a source of oxygen in the fuel mixture for rockets and torpedoes.


This is an enzyme that is found in potatoes. It reacts with a substrate and gives off gas. This is a catalyst. The catalyst speeds up the reaction I am conducting.

Research on Enzyme Reactions

In my experiment this is a diagram of what will happen.

The enzyme will be Catalyse.

The substrate is hydrogen peroxide diluted with different amount of water.

For the reaction to take place the two reactants have to fit together like shown above. This is not a flaw in design but a safety precaution, this reassure that enzymes will not react with the wrong substrate

After the enzyme has reacted it can be used again as long as it has been denatured. This is only after the products have been released though.

However enzymes cannot penetrate living cells. They have to be dead before the enzymes can pass through. This is because that the cell membrane would not let through the enzyme. When the cell is dead the cell membrane becomes permeable and the enzyme can pass.

My Plan

For my experiment I will use a measuring test tube so I can change how diluted the hydrogen peroxide is. I will need a test tube to put my potato and hydrogen peroxide in, the test tube will need a bung and a tube for the gas to travel through to a measuring test tube to measure the amount of gas made.

I will keep my experiment a fair test by making sure my amount of water diluting the hydrogen peroxide is exactly what it is meant to be (the amount of hydrogen peroxide will vary as well to always make 10 cubic centimetres). Then I will need to make sure the potato pieces I use will have the same surface area and that all sides have been cut to perfection so the catalyse can leave. Another factor that could affect the reaction is the temperature, so I will have to make sure that the experiments will always be held at room temperature.

My control variables will be the amount of water with the hydrogen peroxide and the potato shape.

My input variable is the amount of water added to the hydrogen peroxide (measured in cubic centimetres).

My output variable will be the amount of gas given off by the reaction measured in cubic centimetres.



I will have to make sure that my experiment will be safe as this could be dangerous to others and myself. The hydrogen peroxide is extremely dangerous and should be used with caution. It is sensitive to light and that is why it is kept in dark coloured containers. Also I must make sure that I always wear goggles when handling it because if it goes into my eyes it could damage my eyesight. The hydrogen peroxide can also blister skin and if I should come into contact with it I should rinse it off with warm water straight away.


My prediction is that the more concentrated the hydrogen peroxide is the more gas will be given off in the reaction.

I believe this because the collision theory.

Also brake fluids are diluted so they are not corrosive; this is not a reaction but is an example of that concentrated acids are more effective whether for the better or worse.

The way I will record my results is by measuring the amount of gas given off in cubic centimetres. I will store this in a table a along with showing how concentrated the solution is.

My Results

I did my experiment and came out with these results.

While conducting my experiment I found that it was difficult to hold a beaker and keep track off time while making sure the tubing was in the water. Therefore I took out a test tube rack to hold my solution of potato, water and hydrogen peroxide.

For some of my results I had to repeat.


I conclude that my prediction was right and that the more concentrated the Hydrogen peroxide was the more bubbles were made in a minute.

From A line graph I found that the line went roughly like this

From that graph I concluded that while the concentration is increasing at the start from around 10 to 70 percent the amount of bubbles made is increasing but at a slow rate, it then speeds up rapidly from 80 to 90 percent. After that it still increases but slower.

I believe that this shows that it takes a certain concentration for an enzyme to start reacting a fast pace, but then when that point is reached the enzymes start to speed up a rapid rate. For my enzyme that concentration amount is 70 percent when it starts to pick up.

I found out that some of my results seemed anomalous and I sometimes consulted with others and then did a repeat test.

I repeated Number 1, which first came to 8 bubbles. At the start it seemed that Number 2 was wrong with 6 as it was less than 8 (number 1) and also that Number 4 had 9 bubbles. However I did all the takings before I jumped to the conclusion that which ones were wrong and that way I found out which takings were inaccurate.


I think that my experiment was fairly accurate, but that errors were probably made, while measuring out small amounts of Hydrogen peroxide and Water. Perhaps if I used a larger quantity of the two if I had made any mistakes it would not be as significant (I would probably make my potato piece bigger as well).

I would do that if I could do the experiment again, but also I would find a method a chopping my potatoes so that they are more accurate.

Other flaws with my investigation include that I couldn’t completely control the temperature; this was due to the fact that other experiments were happening and also there were many other people in the classroom, which gave off body heat. Also heat was made from people move (kinetic heat).

I believe that my experiment was reliable enough to base an explanation, on how concentration of the substrate affects a reaction. However if I did do it again I would expect it to be considerably better using my suggestions.


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