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Investigation of the effect of different carbohydrate substrates on yeast growth

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"Investigation of the effect of different carbohydrate substrates on yeast growth" Yeasts are eukaryotic microorganisms classified in the kingdom Fungi. The cell walls made of Chitin and they can be found virtually everywhere; "on the skin, on some fruits, in the soil and some are airborne" Saccharomyces cerevisiae are the species of yeast to be used in this experiment. They are used in industry due to the secretion of enzymes that they produce which breaks down sugars by two means aerobically or anaerobic. Aerobically (sugar + Oxygen --> Carbon dioxide + Water + 38 ATP energy) and anaerobically (sugar --> Ethanol + Carbon dioxide + 2 ATP) as this experimental investigation is about the growth of yeast, the main equation is the aerobic one due to it provides 38 ATP energy for cell division either by means of mitotic growth (asexual/ budding) which is the more common type of growth or by means of meiosis (sexual reproduction). The energy is necessary for the oxidising the sugar (C6H12O6/ glucose) into pyruvate, glycolysis happens in the cytoplasm. I will experiment three different sugars; glucose a monosaccharide; maltose a disaccharide and sucrose Alternative hypothesis Glucose will have the largest effect on yeast growth. ...read more.


3. washing hand after experiment will be advised. Procedure 1. I will collect all the apparatus. 2. I will label the test tube 1,2,3 and c; 1 will be the glucose solution affecting the yeasts growth;2 will be the maltose solution affecting the growth of the yeast;3 will be the sucrose solution affecting the yeast growth; c being the control group with no carbohydrate just distilled water 3. I will measure 10 gram of the carbohydrates on the balance pre setting the balance to zero with filter paper on it ass I will only be using the carbohydrates. This 10 grams of the named carbohydrates will be added to 90 cm3 of water to make a 10 % solution of carbohydrate. I will stir the solution for 15 seconds. 4. due to high percentage of yeast I will perform serial dilution making the yeast percentage lower and easier to count underneath the light microscope ast next; 1ml % of yeast into 9ml of solution making it 0.1% yeast then I will pipette 1ml of the 0.1% yeast into 9 ml of solution making the yeast 0.01% and dilte enough to use for counting. ...read more.


0 1 2 3 4 5 6 24 25 26 * * * * * The data and graph Lag time where the yeast cells are not dividing; there is only an increase in cell mass, but not in cell number due to adapting to their environment. Log; time where there's an exponential growth, the population can increase exponentially due to no limiting factors. Stationary time where number of new cells formed is equal to the number of cells dying. Limiting factors, such as nutrient supply, have started to influence further increase in population size. Death; time for autolysis. they have run out of supply and digest themselfs. The statistical test This test will be done to either accept or reject the null hypothesis. The equation below is the one that will be used to work out the value of chi squared. O= the observed result E=the expected result Degree of freedom is the number of environments and subtract one of it. In this experiment 3 -1 = 2 df, 0.05 probability, if the value is less than 5.991 than one can accept with 95% confidence the null hypothesis. ?? ?? ?? ?? Ali Reza Nazokkar A2 Biology coursework planning 1 ...read more.

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Here's what a teacher thought of this essay

4 star(s)

**** A good A-level biology experiment plan, which attempts to present experimental steps and justifications clearly. The rationale lacks A-level biological detail and does not set the investigation in context. To improve:
1)Set the investigation in context, including A-level biology
2)Explain why all control variables should be controlled in term of their potential impact on the growth of yeast, including relevant background biology
3)Ensure that it is clear that each experimental condition (i.e. carbohydrate type in this case) will be repeated the number of times required for the statistical test
4)Justify the statistical test in terms of the effect under investigation and the range or repeats collected
5)Describe how the raw data will be processed, for example yeast cell number should be converted into growth rates to reveal key differences. Cell number is not a measure of growth

Marked by teacher Kerry jackson 29/03/2012

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