Growing Micro-organisms

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Growing Microorganisms

Introduction/ Aim:

Yeast are a tiny form of fungi or plant-like microorganism (visible only under a microscope) that exist in or on all living matter i.e. water, soil, plants, air, etc. The yeast life cycle, like that of all higher organisms, includes a step known as meiosis, where pairs of chromosomes separate to give new combinations of genetic traits. People in today’s society use yeast for controlled fermentation of food and drink; it is also used for baking. In this experiment I will be attempting to measure the growth of a yeast population and in doing this I will have to carry out certain methods to succeed. Below is a diagram on a yeast cells with arrows showing the parts of the yeast cell:

Equipment/ Apparatus:

  • 250cm³ Beaker
  • Measuring cylinder to measure 50cm³
  • A Cuvette
  • A Colorimeter
  • Sticky Labels
  • A Suspension of Yeast
  • Glucose Solution
  • Pipette

Risk Assessment:

This experiment is not that much dangerous so not much precaution is really needed, there are not dangerous chemicals, no hazardous gases etc. Below I have written the things you must look out for when carrying out this experiment.

  • You will be handling many glass equipment when doing this experiment such as beakers and measuring cylinders, you must be extremely careful not to drop or smash the glass in any way or form whatsoever, this could result in the small shards of glass cutting your skin or may even come in contact with important parts of your body such as your eyes.

  • Something else that is important when taking part in the experiment is making sure that the colorimeter does not get in contact with any liquids, this is because the colorimeter is an electrical device and everybody knows that electrical devices do not go with water, be careful when putting your cuvette that will be filled with yeast cells in the colorimeter making sure it does not spill at all.

  • And lastly when you are handling the colorimeter your hands must be dry at all times, you are able to wear gloves at this time of the experiment if you feel more comfortable doing it with them, but when you are plugging the colorimeter your hands must be dry at all times whatsoever.

Fair Testing:

In order to make the experiment more accurate and fair you could’ve repeated the experiment more than once using different methods, but the best thing to do to make the experiment a fair test would be to take three samples instead of one and then finding the mean by adding the three results and dividing it by the amount. There is example of what I mean below with made up results that I have just come up with:

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85         +         86         +         84 =        255,        255        ÷        3 =        85

Another fair test could’ve been that you could keep the temperature constant, by doing this it will allow the yeast cells to grow steadily, if the temperature is high then the yeast cells will die and if the temperature is low this will just prolong the process.

You could also keep constantly stirring the solution as a fair test, this will agitate the solution and the process will quicken, you could also keep providing the yeast population will oxygen because the oxygen acts as an catalyst and speeds up the process.

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