Yeast cells contain enzymes. I am going to investigate the enzyme catalase.

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MARK GLENISTER  64870  8095                01/05/07

YEAST COURSEWORK

PLANNING

INTRODUCTION

Yeast cells contain enzymes.  I am going to investigate the enzyme catalase.  This is how it works:

Hydrogen Peroxide                                   Water + Oxygen

H2O2                                                                                                 H2O + O

I have trapped the yeast cells in jelly, so that when oxygen gas is formed, they rise to the surface.

I will investigate the effect of different temperatures on the enzyme catalase.  To do this I will heat the enzyme to different temperatures and see how long it will take the yeast cells to rise to the surface.

SAFETY AND FAIRNESS

To make sure this will be a safe and fair test I will wear safety goggles and not consume anything in the vicinity of the experiment.

To make sure the results are fair I will use the same size yeast balls, use the same thermometer and same equipment.

PREDICTION

I think that the yeast balls will rise to the top the quickest at about 37ºC. When the hydrogen peroxide is at a greater temperature than this the yeast will take the longest time to rise. At a temperature lower than this then the yeast balls will take longer to rise, but not as long as when the hydrogen peroxide is at a greater temperature than 37ºC.

                     

EQUIPMENT LIST

This is a list of equipment I will need to do the test and a drawing showing how the equipment is set up.

  • Spatula, to transport the yeast balls
  • Test Tube, to contain the yeast balls whilst heating
  • Stop Watch, to time the length of time it takes for the yeast balls to rise
  • Thermometer, to record the temperature at which I will heat the enzymes
  • Hydrogen peroxide, in which the yeast balls go in and then rise to the top of
  • Measuring cylinder, to show the amount of hydrogen peroxide I am putting in the test tube
  • Yeast balls, to rise to the surface of the hydrogen peroxide
  • Test tube rack, to put the test tube once we have heated it
  • Safety goggles, to guard my eyes from heat and danger
  • Bunsen burner, to heat the hydrogen peroxide

VARIABLES

The things you could change are the following, though you mustn't change these things at the same time or the results would not be fair.

  • Size of yeast balls, if you can the size of the yeast balls you are also changing the weight, and so the large the yeast balls the longer it will take for the yeast balls to float to the top, as it will need more oxygen to float.
  • Temperature, the enzymes that make the oxygen needed to make the yeast cells float work best at a certain temperature, if you change the temperature you are changing the enzymes performance level.
  • Environment, humidity etc, The environment could change the quality and content of the hydrogen peroxide, making the solution thinner or thicker, making it easier or harder for the yeast balls to rise.
  • Density of yeast balls, the denser the balls are the more oxygen is needed to make them rise to the top, meaning they will take longer to rise the denser they are.
  • Amount of hydrogen peroxide. If there is more hydrogen peroxide, there will be further for the yeast balls to travel, therefore, the range in the results will be greater, the more hydrogen peroxide there is.
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METHOD

  1. First I put 100mm of hydrogen peroxide each in five test tubes.
  2. Put a thermometer in the test tube.
  3. Heat or cool the hydrogen peroxide until it is at 10ºC.
  4. Take the thermometer out.
  5. Take a stopwatch to one hand and start it when you put the yeast ball in the hydrogen peroxide.
  6. Put the yeast ball in the hydrogen peroxide, stop the stopwatch once the yeast ball has risen to the top.
  7. Record the results.
  8. Repeat the experiment for temperatures, 20ºC, 30ºC, 40ºC, and 50ºC.

PREDICTION

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