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Yeast fermentation

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What effect does sugar have on yeast reproduction? IB Biology Veronika Brantov� May 2008 Defining problem and selection variables Purpose The purpose of this lab is to find out what effect has sugar on yeast in different concentrations of sugar. Background information Yeast is a fungus and needs a supply of energy for its living and growth. Sugar supplies this energy. Yeast can use oxygen to release the energy from sugar in the process called "respiration". So, the more sugar there is, the more active the yeast will be and the faster its growth (up to a certain point - even yeast cannot grow in very strong sugar - such as honey). However, if oxygen is short or not present, then yeast can still release energy from sugar, but in these conditions, its byproducts are alcohol and carbon dioxide. This process is called fermentation. To introduce this laboratory, a number of foods are produced by fermentation such as yogurt, buttermilk, yeast breads, sour cream, etc. Sugars are the common substrate of fermentation. The alcohol and the carbon dioxide are waste products produced by the yeast, which we can see on the equation below. C6H12O6 2CH3CH2OH + 2CO2 + Energy Simple Sugar Etanol Carbon Dioxide Table 1. Comparison of respiration and fermentation of sugar in yeast. Process Conditions Products from sugar Amount of ATP Respiration Aerobic 6 CO2 + 6 38 Fermentation Anaerobic CO2 + 2 C2H6O 2 Hypothesis If we limit the oxygen that ...read more.


Error reduction I made sure that the amount of yeast used in each fermentation flask was the same (because I used a scale). I tried to reduce air us much as possible by rubber stopper. Method of Collection Procedure is proper and goes in order I stated above. Data Flask A - Day 1 Time has passed CO2 produced Total 9:45 0.25hour 0ml - 12:00 2.5hour 1ml - 15:00 5.5hours 1ml - 2ml CO2 Flask A - Day 2 Time has passed CO2 produced Total 8:00 23.5hours 5ml - 12:00 26.5hours 2ml - 15:00 29.5hours 2ml - 9ml CO2 Flask A - Day 3 Time has passed CO2 produced Total amount 8:00 47.5hours 9ml - 9ml CO2 Flask A Total amount CO2 produced that day Day 1 2ml Day 2 9ml Day 4 9ml Together 20ml The amount of carbon dioxide produced in flask A, with one gram of sugar is watched and written down in the charts above the final amount after 47.5 hours is 20ml of CO2. Flask B - Day 1 Time has passed CO2 produced Total 9:45 0.25hour 1ml - 12:00 2.5hour 3ml - 15:00 5.5hours 6ml - 10ml Flask B - Day 2 Time has passed CO2 produced Total 8:00 22.5hour 26ml - 12:00 26.5hour 9ml - 15:00 29.5hours 9ml - 44ml Flask B - Day 3 Time has passed CO2 produced Total 9:45 47.5hour 25ml - 25ml Flask B Total amount CO2 produced that day Day 1 10ml Day ...read more.


Besides that there was the chance that sugar was not dissolved completely Limitations The worst limitation was the problem of lack of time therefore I could not repeat the laboratory process. Besides that supplies were limited therefore I could not use more flasks and beakers to expand my experiment. Improving Ways of improvement The procedure of this experiment could be improved, although the results do give adequate results. Improvements would simply remove certain errors, and improve the accuracy of results: A better overall result would be obtained by repeating the experiment more times. But because the purpose was to show the effect, which I successfully managed to achieve - the result was according to my background information I believe that repetition of the experiment would show slightly different values but the overall result which in this case is the most important would be the same. I should ask another person for help during the preparation time so all testing tubes are set at the same time and not one after another. In order to show better results I could have done one experiment of aerobic respiration and compare the difference. Another idea that may be worth investigating would be the effect of water temperature. So perhaps by increasing the temperature of the solution that the yeast is in, we would see less oxygen in the water at the end of the experiment because more sugar would be in solution and therefore more accessible to the yeast for use. Related to weakness/limitations Using more different concentrations of sugar would have produced a better looking data. ...read more.

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