It is the active site that makes the enzymes specific to what type of molecule it can break down because it needs the correct shape of the active site to fit in with the correct substrate molecule.
Enzymes are in 3 places on the human body, the mouth, stomach and duodenum. They need to be in the mouth to break down large molecules so they can fit down the oesophagus but as the molecules usually are very large they have teeth to help in this part of the procedure of digestion. Once the food is in the stomach the enzymes try again to break down the food yet the molecules are still normally large so there is hydrochloric acid to help still break down the food molecules. Now the food is in the duodenum the substrate food molecules are small enough for the enzyme to break down it down the fastest, and it need to do it now because it is in the small intestine where the food molecules are absorbed through the walls and for it to be absorbed the food needs to be in its smallest structure possible.
In these different places of the body the Ph is different, does this cause the enzyme to work faster or slower or the same?
Aim
To find out if Enzymes work at different rates of breaking down substrates at different Ph’s
Prediction
I can predict from previous experiments when using enzymes and from my own research and reading of enzymes , I feel I can make a good prediction with my own experience and it is; when the enzymes is working in a neutral ph environment (ex. Ph 7) it is working at its fastest and best with the substrate, as long as the enzyme has not been denatured before the experiment which could have been done by heating the enzyme up and damaging it. If the enzyme is in a very alkali or acid environment it will not work as well.
Method
For this experiment we will have to have an enzyme and substrate. We will also have to have an acid. I have chosen these three chemicals to be used in our experiment-
- Enzymes = Liquidised Potato (catalase)
- Substrate = Hydrogen peroxide
- Acid = Hydrochloric acid
To make different Ph’s I will dilute the hydrochloric acid according the Ph I need.
Our apparatus are-
- Test tube
- Bung
- Delivery tube
- Measuring cylinder
- Bowl filled with water
- Litmus paper
I will do the following to keep the experiment safe and fair…
- Wear goggles to stop the acid damaging my eyes.
- Tuck my tie in my shirt.
- Keep my shirt arms rolled up to stop them dragging across the apparatus.
- Keep my book away from the experiment as not to spill water on my results table.
- Keep the same amount of water on the bowl & and the same tempreture.
- Keep the same amount of potato in the test tube
- Keep the same amount of substrate in the test tube
- Keep the same lenth delivery tube if repeating results
- Carry the experiment out in the same room at the same tempreture.
- Make sure the bung is firmly on the test tube and the delivery tube is securely on.
First of all I will set up the experiment as shown on the page before, making sure the water has filled the measuring cylinder fully. Then I will put the Acid in the test tube then test with the litmus paper to see what Ph it is, so I know where to put my result. Then I will add the potato and hydrogen peroxide making sure for every time I do the experiment there is the same volume of each. Then as soon as the chemicals are added together in the test tube I will securely put on the bung with deliverly tube inserted in it. Then making sure the other end of the delivery tube is up in the measuring cylinder I will start the stop watch and after 3minutes exactly, I will read off the volume of oxygen in the measuring cylinder and add the result to my table of results.
Results
Table of results.
Analysis
The experiment did fulfil my prediction of its maximum speed of helping the breakdown the substrate at being Ph 7.
The catalase in the potato was not denatured so the active site worked as it should have, at Ph 7 the catalase in the potato was colliding with the substrate (hydrogen peroxide) at its maximum speed so the active site was hit with the substrate more, as the collision happened the active site would take in the substrate molecule and by twisting the molecule and breaking the molecule apart it would divide the molecule making two instead of one molecule of hydrogen peroxide. As this reaction takes place it creates oxygen so we know from the more oxygen made the more successful collisions have been made. I did have a couple of wrong results that took place in my 1st experiment but I redid them and found the correct result that fitted correctly into my graph.
Conclusion
The experiment went well, and it did what I expected; I did get some false results in my experiment but I managed to redo them. The initial result could have happened from a bubble of oxygen missing the measuring cylinder, or the cylinder being lifted slightly too much and air getting into the cylinder. I could have overcome this problem by using a gas syringe that would probably have been more accurate and less easy for gas to escape from.
My results can be trusted to be correct as I did do them in safe and fair conditions and only a couple of results go stray of the pattern of the others.
I have found that the enzyme catalase works to its maximum at Ph 7 which is a neutral Ph.
