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Multiplication of yeast cells in aerobic and anaerobic conditions

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Practical #3 Multiplication of yeast cells in aerobic and anaerobic conditions Introduction: On hand-out Hypothesis: On hand-out Materials / Apparatus List: Three conical flasks: 100ml 250ml 500ml Pipette Apple juice/yeast solution (provided by Dr. Hebel) Light microscope Haemocytometer Special slide with grid (included with the haemocytometer) Cover slips (included with the haemocytometer) Slide Counter (to count the number of yeast cells. Not necessary but useful) Water bath Rubber bands and tissue (to seal the flasks for the 2nd of the experiment) Methods: On hand-out Variables: Independent --> Size of the flask Surface area of flask Dependent --> Number of cells pr. ml. Data collection: In order to have a fair experiment, we chose to count the number of yeast cells in completely random blocks rather to count the blocks systematically. The reason for this is if we chose randomly, we would have a clearer view of the true number of yeast cells, also it could have been that the yeast cells were not distributed evenly in the sample among the blocks, whether due to the flask not being shaken enough or by coincidence. First series of tests: 100ml flask 250ml flask 500ml flask Trial I Trial II Trial I Trial II Trial I Trial II 10 19 15 ...read more.


and each B-square is 0.04mm�. You can also choose to multiply by 250000. You get the same results. Flasks Another example is the flasks circumference. The flask circumference (110ml of H20) is as follows: 100ml = 15.0 cm 250ml = 25.0 cm 500ml = 32.8 cm This shows the general increase in the flasks surface area and puts into a brighter light of how big the differences between the different ratios actually are. The way you do this is by using the formula: C= 2piR. So to get the area you just use the formula: pi * R�. The Surface area is going to be 100ml = 17.9 250ml = 49.74 500ml = 85.61 So the surface area to volume ration is going to be 1:0.16, 1:0.45, 1:0.78.. switch the one and the decimal around Percentage Increase: 100ml flask 250ml flask 500ml flask 619.9% 793.1% 813.5% This shows that the larger the surface area of the flask, the more oxygen and therefore a faster and more efficient aerobic cell respiration. The way I found the averages was by taking the second sets of results (the ones taken 2 days after the experiment begun) ...read more.


We noticed that the yeast cells had a tendency of 'clumping' together instead of being spread out evenly. This could be due to one of the two microscopes we used was faulty. Because of the time limit, we were forced to keep the results we had which probably also contribute to why the 3rd day results of the 250ml flask are a bit odd as those were the results we got with the faulty microscope. The second part of our experiment we were running short of time and decided to use two light microscopes, as I mentioned before. We discovered that this saved a lot of time and afterwards we concluded that we should've used at least two light microscopes to begin with. This way we would've been able to have enough time to redo the specimens and repeat the experiment. This was not the case for the second part of our experiment, as noted in the previous paragraph. Another explanation could be that we rushed the counting and counted either too many cells or too few. If we had the chance to redo this lab, there are a lot of things I would do properly the second time. First, most obviously being, making proper samples, as well as incorporate all the other ideas that I mentioned above. Thomas Grome Page 1 1/05/2007 ...read more.

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