Enzymes at work

 

In my preliminary plan, I will investigate how much oxygen is produced when the enzyme hydrogen peroxide and some slices of potato are added together. This experiment is very similar to the celery one with the exception that it is potato slices not celery slices. This experiment will give me an idea on what I should change or keep the same. It will also make me aware of the other variables in the experiment and what I need to change about them to get the best results. The enzyme is also strongly affected by temperature; hydrogen bonds are easily disrupted by increasing temperature. This, in turn, may disrupt the shape of the enzyme so that its affinity for its substrate diminishes. We must take into consideration this and I will explore what affect the temperature can have on the enzyme in my preliminary plan.

 For this experiment I will need:

1. Stop clock
2. Cork borer
3. Inverted burette
4. Potato
5. Safety equipment e.g. safety goggles
6. thermometer
7. conical flask
8. gas measuring cylinder
9. clamp
10. 500ml beaker
11. 10ml syringes
12. solutions
13. delivery tube

I will set my equipment up so it looks like this.

From my experiment I came up with these results.

I decided to stop recording at 50C0because the enzyme was denatured and bad low results were coming out, the oxygen given off was poor. The optimum temperature seems to be 35C0.35C0 is not too high or too low and is about the body temperature. I didn’t get 37C0 because I was working in 5C0 each time not measuring 1C0, I will not use this in my test because It will be time consuming and I can still get accurate results with room temperature as long as the temperature stays the same. The optimum time is as long as possible and the optimum amount of potato is as much as you can get but I used 15, in my actual experiment I will use less because it is time consuming to use any more. To make the experiment a fair test I must consider the variables and what I will change and keep the same. The only variable I will continually change throughout the experiment is the pH, I will keep everything else at a set amount and not change it throughout my experiment. I will use my preliminary plan on helping me discover what would be give me the best results.

Plan

I will use:

• Conical flask
• Goggles
• Gas measuring cylinder
• Delivery tube
• 500ml beaker
• Clamp
• Stop watch
• 10ml syringe
• Solutions
• Celery

I will:

1. Collect my equipment and safety equipment
2. Fill the beaker with water. Fill the gas cylinder up with water and put it upside down in the beaker making sure not to let any leak out, then hold it in place with a clamp.
3. Crush up some celery (5ml) and place it in a conical flask making sure to measure out the right amount.
4. Extract some peroxidase (5ml) from the flask, making sure to get the right amount and put it in the conical flask.
5. Do the same with the pH acid/alkali (10ml) and place that in the conical flask.
6. Quickly place the delivery tube on top so that it collects the gas, oxygen, and then start the stop clock.
7. Record the level of the water every 30 seconds/ 60 seconds.

To carry out the investigation I will have to consider these variables:

• Temperature
• Amount Celery/Peroxidase/pH
• Time between recordings
• pH
• Quantity variables

To carry out the investigation I will need to:

• Change the pH of acid/alkali
• Quantity variables

I will keep the:

• Amount of celery, peroxidase and pH the same
• Time between recordings the same
• Temperature the same

Here is what it will look like:

These are the results I came up with from my experiment:

I will use the thirty-second results because the sixty-second results are inconsistent and we can get a much better view from the thirty-second results. I will also use a select thirty-second results as some of the results were random and there wasn’t any pattern. The best results from each test were taken.

As you can see the optimum pH seems to be pH7, just as I predicted.  A rate higher or lower than this, would mean a slower rate of reaction. This is what I said in my prediction.

From my graph, I can see that the curve goes up then down reaching its peak at pH 7. This tells me that this is the optimum temperature and because all of my points are consistent it means that the test is relatively accurate. The curve also shows that any pH above or below pH 7 the enzymes will not fit the active site and will change shape, like this:

As you can see the denatured enzyme cannot react with the active site, it works by a ‘lock and key’ system where only one type of enzyme can react with the active site, this enzyme could react if it had not have been denatured. The enzyme’s active site has a shape closely complementary to the substrate, the substrate cannot lock into the active site of the enzyme, and the enzyme cannot lock into the active site of the substrate.

I have said this in my prediction therefore I am correct in saying the optimum pH is pH 7. This is because enzymes are found in cells and the pH of pure water is pH 7, what I am trying to say is that most of a cell is made up of water which has been filtered and is near enough pH 7. The body will of adapted to suit this and so will the enzyme, this is why the optimum pH is pH 7. The temperature also plays a big role in how the enzyme reacts, for my experiment I kept it at room temperature but for the enzyme to work better it would have to be at the body’s temperature.

If I was to do this experiment again I think I would try and change the temperature so that it suits the enzyme more. I would also try and get the celery to be the same age because my experiments over two days with two different celeries, which could have had an effect and gave odd results. The odd results could of came from anything though, we could of measured slightly wrong, measured the solutions wrong, or when we did measure the solutions there could have been leftover acid in the syringes. I was able to get sensible results in the end after redoing the tests that had odd results. But overall I successfully carried out my investigation fairly and accurately. My experiment was good because I have measured all my solutions accurate, added the solutions together in the same order, timed my experiment to the best of my ability, I have kept the temperature the same and I have produced an experiment that is fair and accurate.