Investigate if the rate of reaction between Hydrogen peroxide and the enzymes on a potato would increase if the surface area was increased too.

Rumel Ahmed 3873

Enzymes Coursework

Aim: To investigate if the rate of reaction between Hydrogen peroxide and the enzymes on a potato would increase if the surface area was increased too.

An enzyme is any one of many specialized organic substances, composed of polymers of amino acids that act as catalysts to regulate the speed of the many chemical reactions involved in the metabolism of living organisms.

Enzymes are large proteins that speed up chemical reactions. In their globular structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. Enzyme and substrate do not bind if their shapes do not match exactly. This ensures that the enzyme does not aid in the wrong reaction. The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate.

Enzymes are extraordinarily efficient. Minute quantities of an enzyme can accomplish at low temperatures what would require violent conditions and high temperatures by ordinary chemical means. Each enzyme is selectively specific for the substance in which it causes a reaction and is most effective at a temperature peculiar to it. Although an increase in temperature may accelerate a reaction, enzymes are unstable when heated, when at temperatures of 45° or above the enzyme denatures which renders it useless. Many enzymes require the presence of another ion or a molecule called a cofactor, in order to function.

As a rule, enzymes do not attack living cells. As soon as a cell dies, however, enzymes that break down protein rapidly digest it. The resistance of the living cell is due to the enzyme's inability to pass through the membrane of the cell as long as the cell lives. When the cell dies, its membrane becomes permeable, and the enzyme can then enter the cell and destroy the protein within it.

There are a few factors that affect how fast the enzymes work, they are listed below-

Temperature

The temperature at which the enzymes are placed in are very important, the enzymes performance will get better and better as the temperature goes up but at the crucial mark of 45° the enzymes begin to denature, once the enzyme is denatured the process cannot be reversed.

Surface area

The surface area also affects the speed at which the enzymes work. The enzymes in my experiment will come from the potato. As the potato is a solid only the enzymes on the surface of the strip of potato will be in the reaction. So as the surface are increases the number of enzymes exposed will increase to.

Time

As time passes the enzymes begin to work faster and faster, this would increase the speed at which the reaction takes place.

Preliminary experiment

The reason that I am going to do a preliminary investigation is that I ...

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Surface area

Time

As time passes the enzymes begin to work faster and faster, this would increase the speed at which the reaction takes place.

Preliminary experiment

The reason that I am going to do a preliminary investigation is that I will know what I have to do in the main investigation without making any mistakes. This is where all the mistakes happen. If a mistake happens I can learn from it. I want to make sure I am using the right amount of hydrogen peroxide and if the intervals between the surface area will be provide me with a reliable set of data.

For the experiment I will cut out cylindrical sticks out of the potato, each time I want to increase the surface area I will cut the stick in half and then in quarters and so on.

Method for Preliminary Investigation

Set up the apparatus
Work out a suitable length of the strip of potato
Find out a suitable amount of hydrogen peroxide that can be used in the experiment
Find out how to work out how much oxygen is given out
To keep these factors constant during the experiment.

Temperature
The length of the potato

The amount of hydrogen peroxide
To carry all the experiments over the same length of time

After doing the preliminary investigation I had collected the correct information on how to make this experiment as safe as possible and how to get the most accurate results.

These are the following-

The correct equipment that I will have to use.
I will need to use a cylindrical strip of potato that is 5cm long
I will need to use 30ml of hydrogen peroxide
To increase the surface area I will need to cut the strip of potato in half then into quarters and then into eighths and then to sixteenths and finally thirty twos
The experiment should be carried over a time of 5 minutes
I will need to do the experiment 2 times to get more accurate readings.

The Apparatus

This is the list of the apparatus that I will use in the experiment-

Borer
Hydrogen peroxide with a concentration of 30 volume
Potato
Thermometer
Conical flask
A water bowl
50ml measuring cylinder (2)
Cork with tube
Stop watch
Knife
Ruler

This is a diagram of how I will set up the experiment.

Method

Firstly I will need my stick of potato, so I will use the borer to cut a cylinder of potato out of the potato. I will then cut down the piece of potato so that its length is reduced to 5 cm by using the ruler and knife. Then I will need to set up the other pieces of apparatus. The plastic bowl will need to be filled to the top with water, then I will need to place on of the measuring cylinder into the water and fill it up will the water. once it is filled I will need to flip the measuring cylinder inside the water so that air can get into it. It is very important that there are no air bubbles left in the measuring cylinder. After that I will place one end of the tube inside the measuring cylinder making sure that the end without the cork is place in. Now I have to measure 30ml of Hydrogen peroxide with the other measuring cylinder and pour it all into the conical flask. Finally its just a case of placing the strip of potato into the flask and putting the cork with the tube on top of the flask and start timing.

This is how the experiment works, when the reaction takes place oxygen is released as a product of it, as it is released it travels along into the tube and goes straight into the measuring cylinder. When the oxygen enters the cylinder it displaces the water in it and collects at the top of the cylinder, this happens because the oxygen is lighter than the water and can push it aside so that it can reach the top. Once the oxygen is collected we can measure how much has collected in it with the markings on the cylinder.

I am going to vary the surface area of the potato through out the experiment, and control all of the other variables.

I shall only be altering the surface area of the potato by cutting the strip of potato into pieces, as that is my main variable, and so I will therefore keep the others the same in order to make it a fair test. I will keep my variables the same by making sure that I have implied the same strategy for each test taken. The amount of Hydrogen Peroxide is carefully measured out using the measuring cylinder; enabling me to make sure it is kept constant throughout the experiment.

Safety Precautions

I will have to be careful when using the Hydrogen Peroxide, as it is a corrosive chemical, so I will attempt to overcome this problem by wearing goggles.

Hypothesis

My hypothesis is that as the strip of potato is cut into more and more pieces there will be more surface area exposed to the hydrogen peroxide. This means that there will be more enzymes participating in the reaction, which will make the reaction happen even faster.

Predictions

I predict that as the surface are increases there will be more oxygen released from the reaction. And also in most cases the amount of oxygen collected will double when the surface area doubles.

Results

Here are the results of the experiment, I did the experiment twice and got an average from them, to get the surface area of the potato I first found out the circumference of the top of the cylinder and multiplied by the length which was 5cm and I added that to the area of the ends of the cylinder which was pi multiplied by the radius squared that gave me the surface are of the stick when the stick was whole.

Analysis

From the results above I drew a graph (see graph 1). Straight away from the graph I can see that my hypothesis was correct. I can see that there was more oxygen being released from the reaction when the potato was cut up into more and more pieces. There is a steady curve going up wards which means that there is actually more oxygen being released as more surface area is exposed. If more oxygen is being produced then it is logical to assume that the reaction is happening faster with the aid of the enzymes.

I know that the increase of the surface area made the reaction happen faster because the other variables that can affect the speed of which the reaction takes place cannot have interfered with the results as they were controlled.

I also predicted that if the surface area doubled then the amount of oxygen doubled. That I couldn’t measure properly it properly. I couldn’t get enough data, I had surface areas that didn’t go up in the same interval because I had calculated the surface area from the number of times the stick was cut in half. That meant that none of them could be doubled properly. Some of them could be almost doubled properly and from them I could see that I was right.

Evaluation

Although I conducted the experiment as accurately as I could there were many sources of error in the method that I used. Firstly when I used the tube to carry all the oxygen that was released to the measuring cylinder in the bowl I had to take one end of the tube and place it in the water so that it could be placed in the measuring cylinder. As I did, water would often enter the tube and block it, this would prevent the oxygen from coming out the tube, some would eventually come out towards the end of the experiment. This would make some of the results inaccurate.

Also another problem was that I used two different potatoes, the first one was full of holes, so I had to use another one, the second potato might have had a higher or even a slightly lower concentration of enzymes and that will most certainly have change the results of the experiment. Other errors that might have occurred during the experiment might have been when the measuring cylinder was being filled with water, there might have been small pockets of air that was trapped and went unnoticed. This might have made the results seem larger than they should be.

Another is human error. To measure the hydrogen peroxide I had to use the measuring cylinder which involves using the human eye to get an accurate reading, the human eye can sometimes be deceiving, the wrong amount of hydrogen peroxide might have been used, this would have affected the results.

A combination of human error and faulty equipment could render the experiment a failure. Sometimes people rush things and takes down a wrong reading and also faulty equipment can sometimes give wrong readings.

The method of the experiment could probably also be improved to obtain more reliable results.

Due to the nature and convenience of the experiment, it could be easily modified to investigate another factor. I investigated the Surface area when I could have investigated the Concentration or the temperature, by investigating them I could have got better results but controlling the temperature would have been really difficult, putting in all that effort might not have been worth it.

The evidence that I obtained is sufficient enough to support the conclusions I have made. Because I conducted my experiment as accurately as I could with the method I used.

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