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The aim of doing this experiment is to investigate how the different type of substrate has an effect on the rate of yeast's population.

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Introduction

Monitoring the Growth of a Micro-organism Introduction The aim of doing this experiment is to investigate how the different type of substrate has an effect on the rate of yeast's population. The independent variable of this experiment will be the different type of substrate. The substrate I am going to use in this experiment are monosaccrides glucose and fructose, disaccharide sucrose and polysaccharide starch. Yeast uses the energy from sugars for growth and asexual reproduction. So the size of yeast population will increase as the time increase. Therefore the dependent variable of this experiment will be the number of yeast that will be counted. There are so many reasons affecting the rate of growth of yeast. These are the availability of nutrients, the temperature and the PH of yeast's environment. Therefore I will need to control these factors, so that they will stay the same and no effect on yeast population apart from changing the amount of glucose in solution. Also the amount of will be kept constant, to ensure only that the size of yeast population is affected by the different type of substrates. Hypothesis I predict that yeast in each solution will not grow at constant rate. ...read more.

Middle

Label each boiling tube with a number. 1, 2, 3, 4, 5. All boiling tubes except boiling tube 5, will be added yeast, sugar and water. Boiling tube 5 will not be added sugar, to see as a control experiment, in order to see whether sugar have an effect on growth of yeast population. 3. Fill each boiling tube with 1 ml of yeast solution by 1ml piptte. 5. Pour 9ml of glucose in boiling tube 1. Pour 9ml of fructose in boiling tube 2. Pour 9ml of sucrose in boiling tube 3. Pour 9ml of starch in boiling tube 4. Pour 9ml of water in boiling tube 5. 6. Use a clean stirrer and thoroughly stir boiling tube 1 to stop yeast cells clumping together. Stirring of the solution in the boiling tube is required before sample solution is taken for counting in order to prevent yeast cells from clumping, so that it will be easier to count the number of yeast cells on B square. Otherwise, clumping can cause inaccuracy results in number of cells counting. 7. Count number of cells using haemocytometer under light microscope. * Drop the sample from boiling tube 1 onto haemocytometer using clean pipette. ...read more.

Conclusion

Following calculation is as example that show how to find number of yeast in 10 cm3 of liquid. 1. Mean of yeast cells in 5 type B square Say 1st reading - 52 2nd reading - 54 Add 52 and 54 and then divide by number of reading which is 2. 52 + 54= 106/2 = 53 yeast cells So there are 53 yeast cells in 5 B type square 2.Find number of yeast in A type square 1 A square = 25 B square so 5 * 53 = 265 yeast cells Volume of A square is 0.1 mm3. So 256 yeast cells in 0.1 mm3. 3. Find number of yeast cells in 1 cm3 1 cm3 = 1000 mm3 so 1000 * 265 = 4. Find number of yeast cells in 10 cm3 1 cm3 = 265,000 yeast cells 10 cm3 = 265000 * 10 = 2,650,000 yeast cells Rate of yeast per day = total number of yeast in 5 days / time taken (5 days) Standard deviation ? = sum of n = the number of values x = each value in data set Graph that I am going to plot for my results Number yeast again days ( all 5 different substrates on one graph for comparison) rate of yeast growth against 5 different type of substrates ...read more.

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