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BiologY Lab report

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BIOLOGY LAB REPORT Aim: Design an investigation to measure the effect that one of the following factor has, on the rate of respiration in yeast. Hypothesis The factor that I have chosen to vary in this experiment is types of carbohydrates used. I think that respiration of the yeast cells greatly depends upon the type of carbohydrate used here is an example supporting my statement: yeast might readily react with Glucose whereas it might not react at all with Lactose. This might be mainly due to the fact that Glucose generally being a simple sugar Is chemically active and is more of an acid, thus makes it easier for yeast cells to break down the molecules producing Ethanol and Carbon dioxide. Whereas Lactose doesn't react that well because Lactose being a complex sugar and a disaccharide takes up a lot of time for yeast to metabolize... Apparatus required 1. Yeast - 15ml 2. Test tubes - 2 3. A syringe 4. Sucrose - 12ml 5. Glucose - 12ml 6. ...read more.


Keep the test tube 1 containing the mixture of yeast + carbohydrate immersed in the water bath i.e in the large sized beaker containing hot water. 9. Now pour in water (not hot water) in test tube 2 and keep the interconnecting tube inserted in the water of test tube 2. 10. After that connect the INTERCONNECTING tube and seal it with cork on both test tubes, this is generally done to ensure that the yeast respires anaerobically . 11. Initially wait for about 5minutes and then start counting the no of bubbles that pop out for the next 5minutes ..... Note : ENSURE THAT BOTH TEST TUBES ARE PROPERLY SEALED. 12. To keep temperature constant keep adding hot water when the temperature of the water in water bath comes down.. or if the temperature has raised then add considerable amount of cold water needed to bring down the temperature.... 13. Repeat this investigative from steps 6-12 using different types of carbohydrates... and record the no of bubbles popped out in test tube 2. ...read more.


I think that main flaw of my experiment was improper sealing of the test tubes during the reaction since improper sealing could lead to wrong or improper readings. Questions and Answers Questions Why some sugars were not metabolized while other sugars were? Why do you need to incubate the yeast before starting to monitor the bubbles? Considering the results of my experiment, do yeast equally utilize all sugars? Answers Yeast may not have the proper enzymes to either transport lactose across its cell membrane, or it may not have the enzyme needed to convert it from a disaccharide to a monosaccharide. The yeast need to be incubated so that the oxygen in the test tube will be completely consumed. If the yeast respire aerobically, no bubbles would occur, because much oxygen is consumed as CO2 is produced. It also takes a few minutes for the yeast to transport the sugar into the cell, to respire at a constant rate, and to reach the proper temperature. Yeast cannot utilize all of the sugars equally well. While glucose, sucrose, and fructose all can be metabolized by yeast, lactose is not utilized at all. ?? ?? ?? ?? ARUL VERMAN .R ...read more.

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Here's what a teacher thought of this essay

3 star(s)

A reasonable write up that would benefit from a little more research into the structure of sugars and how they can be broken down. 3 stars.

Marked by teacher Louise Star 08/01/2013

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