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Effect of different substrates on fermentation by Yeast.

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Introduction

Effect of Different Substrates on Fermentation by Yeast Background: Yeast respire anaerobicly Glucose � ethanol + CO2 ( + 2ATP ) Aim: To find the effect of different substrates on fermentation by yeast. Apparatus: Bunsen Burner Boss Safety Mat Trough Tripod Stop Clock Gauze Scales Beaker Boats Thermometer Matches 6 Test Tubes Pipette Bung Spatula Delivery Tube Oil Measuring cylinder Yeast Water Substrates (Glucose, Fructose & Starch) Clamp Stand Diagram: Hypothesis: In my investigation I will change the different substrates & measure the amount of Carbon Dioxide gas collected. Using a monosaccharide (Glucose), a disaccharide (Fructose), and a polysaccharide (Starch) as the substrates. I think that the glucose will produce the most Carbon Dioxide gas, as it is a monosaccharide, and will be easier to break down as it has fewer bonds to break. ...read more.

Middle

(ml) Start End Total Start End Total Monosaccharide 0.0 0.0 0.0 0.5 2.5 2.0 1.0 Disaccharide 0.0 0.5 0.5 2.5 3.0 0.5 0.5 Polysaccharide 0.5 0.5 0.0 3.0 5.5 2.5 1.3 Observations: Glucose produced the most amount of froth, and starch the least. Graph: See over page. Conclusion: I have found the effect of different substrates on fermentation by yeast. From my results I can see that the polysaccharide produced the most carbon dioxide, and the disaccharide the least amount. The polysaccharide (Starch) produced 1.3ml of Carbon Dioxide, and the disaccharide (Fructose) only 0.5ml. This is clearly shown on my graph. Evaluation: The results that I have gained are not reliable. This is because the first set of results taken was clearly wrong. I thought that there might have been an air leak in the bung or delivery tube, so I changed them for the second set of results, which appeared to work better. ...read more.

Conclusion

There may have been a leak in the delivery tube or bung, as I discovered in my first attempt, and so the results would be inaccurate. If the measuring cylinder were tilted when I read off my results then I would have inaccurate data. Because of these inaccuracies, I believe that all of my results are anomalies. If I were to improve on this experiment, and do it again I would change a few things. I would try to prevent air escaping by putting Vaseline around the rim of the bung, I would repeat all of my results at least 3 times to make them accurate and reliable. I would try to ensure I did not heat the water higher then 40�C so not to denature the enzymes, I would shake the contents to make sure all the substrate was dissolved, and I would make sure there was enough of both enzyme and substrate. This would make my results a lot more accurate and reliable. ...read more.

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Here's what a teacher thought of this essay

4 star(s)

This is a good write up but it lacks a little bit of depth in places. It shows a little confusion on the molecules used that could easily be sorted out by including some diagrams.

It could be enhanced by trying to expand a little on some of the failings in the results. The writer could try and explain why they got some of the results rather than simply stating it. Some more technical vocabulary would also help.

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Marked by teacher Sam Morran 15/05/2013

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