The Effect of Temperature on the Rate of Reaction of the Enzyme Catalayse and Hydrogen Peroxide

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Wednesday 17th January 2001

The Effect of Temperature on the Rate of Reaction of the Enzyme Catalayse and Hydrogen Peroxide;

Aim;

        The effect of temperature on the rate at which enzymes work.

Method;

        We set up the experiment as shown;

Based upon a preliminary experiment we have decided to carry out the experiment as shown…

  1. Extract the enzyme catalayse from 2g of celery by crushing with a pestle and mortar and adding 2ml of water.
  2. Heat a water bath over a Bunsen burner until it reaches the desired temperature. This temperature will be maintained until the water is needed.
  3. We will then place 5ml of H2O2 into a conical flask using a pippet and measuring cylinder. This chronicle flask will then be placed into the water bath, which has now been taken of the heat.
  4. While the heat is equilibrating between the two liquids to the desired temperature (e.g. 50º C), we will fill an ice cream tub with water and invert a measuring cylinder full of water into the tub.
  5. We will then add the celery paste containing the catalayse (which we crushed up in stage 1) into the conical flask containing the substrate H2O2. After doing this we will quickly place the cork (with a tube running through it) into the conical flask and quickly insert the delivery tube into the inverted measuring cylinder in the ice cream tub.
  6. The reaction will then take place and the oxygen given off will then travel through the tube displacing the water in the inverted measuring cylinder. We will record the results on the basis of how much oxygen the reaction produces after a certain amount of time.

Apparatus;

  • Bench mat
  • Celery (Containing the enzyme catalyse)
  • Conical Flask
  • Cork
  • Delivery tube
  • Gauze mat
  • Hydrogen Peroxide
  • Ice cream tub
  • Pestle and mortar
  • Pippet
  • Thermometer
  • Timer
  • Tripod
  • Two measuring cylinders
  • Water
  • Water bath (beaker)

Planning

        Due to a preliminary experiment I found an optimal temperature range of about 0-60°C because I realise that enzymes denature at about 50°C and beyond. This decision was also based upon our preliminary experiment.

From my reading in ‘Biology – a functional approach, (Nelson)’ the following points can affect enzymes and so can be listed as possible variables;

  1. The effect of temperature on enzyme activity.
  2. The effect of pH or substrate on enzyme activity.

I have chosen temperature as a variable. This is because it is easier and simpler to work with allowing us to focus on more accurate results to be obtained. There is also a broader range on which results can be obtained as you can go to a greater degree of accuracy e.g. 0,5,10,15,20,25,30-60 (concerning temperature) instead of 1,2,3,4,5,6,7-14 (concerning pH). It is also easier to control the temperature level than pH because it can be quite hard to obtain exactly the right pH level. It is also more dangerous when using pH as the variable because when we get to the more concentrated levels we will have to be careful as hydrogen peroxide can cause blistering on contact with the skin.

Temperature is my only variable and shall be carried out in 10°C intervals giving me 7 readings with a range of 0-70°C. We will repeat each experiment three times from which an average can easily be obtained. This will also rule out any anomalous results, which don’t fit the expected pattern. The desired temperatures will be achieved using a Bunsen burner. I must make sure that now that I have chosen temperature as my variable that the other main variable pH is controlled and watched so that it doesn’t affect the experiment.

To measure the effect that temperature has on the activity of the enzyme we shall put the catalayse together with the hydrogen peroxide in a conical flask. We will then seal the conical flask with a cork which has a tube connected through it. This tube will lead into a measuring cylinder full of water, which has been inverted in a tub full of water. As the reaction takes place within the conical flask (which we found happens almost instantly) the gaseous product formed from the H2O2 (O2) rises out through the cork and along the tube rising up the inverted measuring cylinder. The following is the reaction taking place:

Catalayse + Hydrogen peroxide                              Catalayse + Oxygen + Water

                         H2O2                              Various temperatures                                       O2            H2O  

 The oxygen then displaces the water in the measuring cylinder as it fills up. We will then record the results on a basis of how much oxygen entered the measuring cylinder after a certain amount of time. We have decided that the time taken for each experiment to take place in should be about sixty seconds. We decided upon this amount of time because if we had it any shorter we found that the greater part of the reaction had not been completed. If we had left it longer the results would not have been as accurate as the oxygen bubbles begin to be produced at random rates, slowing down and being released every now and then. Also, the measuring cylinders with the greater degrees of accuracy did not have a large enough capacity to hold all the oxygen given off through the whole reaction (from the point it begins to the point the reaction stops).

Join now!

 We carried out a preliminary experiment to see whether our original plan worked. It highlighted a few problems such as the amount of hydrogen peroxide we used. We discovered that if we used too much then the reaction would be over too quickly so we had to reduce the amount of H2O2 we used to 5ml. We also realised that 2g of celery was an adequate amount to be used. As well as the preliminary experiment highlighting some errors with our method it also enabled us to see whether all the equipment worked well with each other providing the most accurate ...

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