I want to find out if the concentration of the Hydrogen Peroxide affects the speed at which the potato gives off gas.

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Philip Singer, 11W1 Biology Coursework

Catalase Investigation

Aim:

  • I want to find out if the concentration of the Hydrogen Peroxide affects the speed at which the potato gives off gas.

Planning

Enzymes like catalase are protein molecules that are found in living cells. They are used to speed up reactions within the cell, and so are biological catalysts. Catalysts speed up reactions but they are not changed during the reaction.

Enzymes only work on one specific type of substrate that means that there is only one kind of substrate that will fit into the enzyme’s active site. Most enzymes optimum working temperature is 37°C (body temperature).

Catalase is found in food such as potato that I will be using in my experiment. They are all very specific as each enzyme is used for different jobs. Catalase is used for removing Hydrogen Peroxide from the cells. Catalase is used to speed up the decomposition of the Hydrogen peroxide into water and oxygen.

Preliminary experiment

First of all I did a preliminary experiment, when we picked 15 potato chips at random and cut them down to the same length using a razor blade, making them even. I then set up the equipment as shown below and injected the hydrogen peroxide solution, and timed how long it took for 1ml of gas to be displaced as the H2O2 is attacked by the enzymes in the potato.

⇑ Fig 1. Equipment setup

To do this I will use the following:

  • Potato chips
  • Test tubes
  • Syringe
  • Bungs
  • Burette
  • Linking tube
  • Trough for water
  • Water
  • Hydrogen Peroxide
  • Razor blade and cutting tile

To keep it the same I will always use the same size of chip, and keep the surrounding temperature the same by doing it in the same place throughout the experiment. If I were to change the temperature as I was doing the experiment I would probably end up with anomalies or irregular results to everyone else.

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I intend to vary the concentration of the hydrogen peroxide by changing the amount of water it is mixed with, so that for every five millilitres the amount of water will be either none, 1 ml, 2m, 3ml or 4ml to every 5ml/4ml/3ml/2ml/1ml of hydrogen peroxide.

I was unable to achieve any results as part of the preliminary experiment because the gas travelled too quickly down the burette, so in the real experiment I will have to time how long it takes to go to 5ml instead of 1 ml.

Reasons for a preliminary Experiment

We ...

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