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# Yeast lab. Question: how does the yeast concentration affect the rate of anaerobic respiration?? Measured by the concentration of released CO2.

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Introduction

Yeast fermentation experiment Design: Question: how does the yeast concentration affect the rate of anaerobic respiration?? Measured by the concentration of released CO2. Main goal (aim): tracking the relationship between the rate of anaerobic respiration and the yeast concentration. Hypothesis: Two types of cell respiration exist, aerobic and anaerobic respiration; anaerobic respiration takes place when there is no enough oxygen for the aerobic respiration, the following equation shows the aerobic respiration: Glucose yeast Ethanol + CO2 + heat. It is obvious by the previous chemical reaction that as the yeast concentration increases, so does the anaerobic respiration. Variables: Independent variable: yeast concentration (a variety of yeast solutions are used, in order to determine the effect of changing yeast concentration on respiration rate). Dependent variable: CO2 (released amounts), representing the rate of respiration. Controlled variables: Variable Why to control How to control Concentration of sucrose Because sucrose is the reactions substrate. ...read more.

Middle

Record the reading after the time has ended (the CO2 censor was calibrated at the beginning and the data collection settings was modified to collect CO2 concentration in ppm for 1 minute intervals.) - Empty the beaker and clean it, before repeating the previous procedure. - Repeat the same procedure for every concentration, 3 times for every single concentration and then obtain the average. - Record the results in a proper table. - Represent results in an explanatory graph. Data collection and processing: Raw data: Table (1): initial and final readings of CO2 evolved for every yeast concentration Concentration of yeast in solution (gm/ml) Trial (1) Trial (2) Trial (3) Initial CO2 reading (�50 ppm) Final CO2 reading (�50 ppm) Initial CO2 reading (�50 ppm) Final CO2 reading (�50 ppm) Initial CO2 reading (�50 ppm) Final CO2 reading (�50 ppm) 2% 5599 13429 7246 18353 7473 19825 4% 9637 26400 7772 22746 6949 28032 6% 8612 37908 7030 36996 7352 32248 8% 7087 37275 6860 41413 7979 39708 ...read more.

Conclusion

Evaluation: 1. A problem was faced in taking volumes, since cylinders were the instrument used, which is a way of error. 2. The cover provided didn't it the opening of the cylinder, thus producing errors. 3. Shaking the solution while reading, differed in the intensity, form one solution to the other. Possible improvements: 1. Use more accurate equipment (pipettes and burettes.... Etc) to take the volumes of yeasts and sucrose. 2. Use an automated machine that does vibration, to make the whole intensity of shaking equal. 3. Use containers or cylinders, which have proper openings for the CO2 sensor, to get more accurate results. 4. Use another apparatus, where the sucrose will be put into a syringe, the syringe attached to a tube, which goes through the test tube, where the yeast will be put, and the tube contains a proper opening for the CO2 reader, and then when everything is set up sucrose will be pumped by the syringe and the reaction would start. ...read more.

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