The action of enzymes.

The Action of Enzymes Aryana Masoudi 11F

Background Information:

Enzymes are proteins that are chemicals that dissolve and break down food. They help speed up the rate of which food can be digested in our bodies. Without enzymes food will take forever to digest, but as they are highly specific catalysts that mean that they can break larger molecules faster then if they were not there at all. Although enzymes are very useful to our bodies they can become useless in extreme conditions as they become denatured, and lose the intricate structure so that they can no longer break down any substrates. Enzymes being catalysts mean that they don’t get used up in the reaction and so can continue to break down any substrates. Enzymes break down substrates by using the lock and key theory. The lock and key theory is a simple way of describing how specific an enzyme is for a substrate. Just like a lock requires a specifically shaped key for it work so does an enzyme. Each enzyme has an active site, which is where the enzyme can bind to the substrate on which it can perform some chemical reaction. Because each enzyme performs a specific task on a substrate the active center of the enzyme can be considered to be the lock which requires a specific key or substrate to the function of breaking it down.

Aim: To investigate how temperature can effect the rate of reaction between an enzyme and a substrate.

Theory: My initial theory is that as the temperature reaches a certain level (optimum temperature) the rate of reaction will increase. As the enzyme reaches its optimum level the rate of reaction will increase causing there to be less trypsin present. The purpose of a catalyst is to make a reaction work without getting used up in the process. If there is no catalyst then any substrates such as glucose or sucrose can ever be digested.

Prediction: My prediction is that as ...

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Aim: To investigate how temperature can effect the rate of reaction between an enzyme and a substrate.

Prediction: My prediction is that as the temperature reaches roughly 40°c that the reaction rate will become quicker. I am saying this because the optimum level of the enzyme is roughly 40°c, anything above 45°c and the enzyme will start to denature and not work properly causing the rate of reaction to decrease. Also if the temperature is below 40°c then the enzyme will work too slow due to temperature. I also think that the rate of reaction will increase because of the collision theory. The collision theory is based on the fact that when the temperature reaches 40°c (optimum level) the Enzymes and substrates will be moving faster meaning that there will be more successful chemical reactions between them. More successful chemical reactions happen because there is enough energy in the chemical reaction to break bonds. This means that there will be more substrates to break down per second, which means there will be more successful substrates being broken down per second, so the rate of reaction will increase. I also predict that the rate of reaction will double after every 10°c. the reason that I predict this is because of the Q10 theory. I also predict that the doubling will stop at roughly 40°c. By using the Q10 theory it means that we are able to predict the results that we are going to get up to and including 40°c.

As is clear from the graph below that the optimum level of an enzyme is roughly 40°c

Preliminary Experiment:

It took on the first repeat 150 seconds for the starch to turn into a negative at a temperature of 30°c.

Then on the second repeat it took 300 seconds for the starch to turn into a negative at a temperature of 30°c.

After we saw the difference of the readings we decided to write down the results in intervals of 10 seconds, rather than 30 seconds so as to make sure that our results are more accurate.

Method:

Collect test tubes.
Collect enzyme trypsin.
Collect a syringe and milk.
Collect tripod, Bunsen burner and heat proof mat.
Collect a stopwatch and thermometer.
Mark a dot on a piece of paper and put it under the test tube.
Lower the test tube in the water at the temperature desired.
Start the stopwatch when the trypsin and casein are in the test tube and at the right temperature.
Stop the stopwatch when the solution goes clear and the dot is clearly visible.
Record the time it took in seconds for the solution to go clear.
Record the results gotten, into a table.
After recording the results repeat the experiment.
As I am taking readings from 0-70°c in steps of 10°c there will be 21 readings including the repeats and also another three readings for my controlled experiment including the repeats.

The Clarity of the test tube will be determined by eye, due to lack of equipment. The stopwatch shall be stopped once the solution has reached its optimum clarity, this could be proved difficult due to the fact that the clarity of the test tube varies as you go up it. This means that our results may have some anomalies occurring in them, these anomalies may be caused by human error or other occurrences with in the experiment like the temperature not remaining constant. This means that our results may not be very accurate.

Variables:

Temperature of solution.

Constants:

Volume of solution.
We will be keeping the same apparatus so as to keep it a fair test.
The pH of the test tube will be kept the same so as to make it a fair test.
The concentration of both the substrate and enzyme will be kept the same.
The fact that we will not shake or stir the test-tube will be kept constant as this would make our results unreliable.

Fair Test:

The reason why we have a fair test is so to make the results as accurate as possible. The ways in which we shall keep it a fair test is to have 3 repetitions of each temperature. Also I shall clean out the apparatus used like the test tube and syringes so as to make sure that out results are not affected through contamination.

Factor of rate of reaction:

The factor that I have chosen to affect the rate of reaction of my experiment will be temperature. The reason for this is that it seems that there is less chance of human error making my results inaccurate.

Safety

During this experiment certain precautions must be made as we are dealing with water in excess of 70°C. The precautions taken were to wear safety goggles, so that our eyes can not get harmed or damaged as a result of a spillage.