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Influence of yeast concentration on rate of cellular respiration

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INFLUENCE OF YEAST CONCENTRATION ON THE RATE OF CELLULAR RESPIRATION Aim: Investigation how the difference in yeast concentration influence the rate of cellular respiration, during the reaction of respiration which product was ethanol and carbon dioxide. Hypothesis: If the yeast concentration is increased, then the amount of CO2 emitted will increase. This is because more yeast are able to produce ATP through cellular respiration. The more yeast are available, the faster the rate of cell respiration, and the more C02 that will be produced. This means the higher the concentration of yeast, the less time is needed to produce the same amount of CO2. VARIABLES INDEPENDENT DEPENDENT CONTROLLED Yeast concentration, which was controlled having constant concentration of sugar Rate of reaction, measured as the time needed for the reaction to reach established point Temperature Mass of sugar Mass of solution Control of variables: The temperature was checked every 30 s during a measurement. No changes in the surrounding were made in order to keep the temperature stable. When the temperature was falling, the solution was heated up using burner until the initial temperature (40�C) was reached. The acceptable change in the temperature was � 0.05 �C. ...read more.


Yeast concentration [%] Mass [g�0.05] Yeast Sugar Water 10.00 2.00 2.00 16.00 20.00 4.00 2.00 14.00 30.00 6.00 2.00 12.00 40.00 8.00 2.00 10.00 The reaction in the experiment has followed the equation: C6H12O6 � 2C2H5OH + 2CO2 At first, the adequate solutions were made. The amount of sugar (2.00 g) was kept the same during all the measurements, only the amount of yeast and water was changed so that the total mass of solution was 20.00 g. Water was measured in cylinders in cm3 so I needed to calculate the mass not volume. Since the density of water is 1g cm-3 the mass of water will numericaly be the same as the volume, just the unit will be changed. Eg. 16.00 cm3 *1g cm-3= 16.00 g Higher yeast concentrations were created by increasing the amount of yeast in the solution and decreasing the amount of water. After creating necessary solutions, the experiment was carried and the measurements were recorded in Table2. Table 2: The time it takes for the fluid to rise through the distance of 5 cm in diversified yeast concentrations Yeast concentration [%] Measurements [s�0.1] First measurement Second measurement Third measurement 10.0 27.2 23.3 20.3 20.0 12.2 13.1 13.6 30.0 11.2 10.5 9.8 40.0 7.5 7.8 8.6 Table3: The average values of time. ...read more.


So as for the rate of reaction, it increases almost linearly between the 10 to 40% yeast concentration. The value of rate of reaction for 20% yeast concentration does not fit perfectly to the other datas. The rate of fermentation will increase proportionally as yeast concentration increases. I was not able to create wider range of solutions with higher yeast concentrations, because of too big amount of yeast in 20g solution; different proportions of substances should be made to wider the range. It was also impossible to create 100% yeast solution, since in each solution created the mass of sugar was kept constant, so that the maximum percentage solution for the fermentation to occur was 90%. It also show how big influence on the rate of reaction has the yeast concentration. Comparing my results with the literature ('Advanced Biology' by M. Kent) where claimed that the rate of fermentation increases with increasing yeast concentration but levels out at some point, the results I obtained were correct (in the range 10 to 40 % yeast concentration). In the experiment there were errors due to: * Significant uncertainities of the equipments which might later influence the measurements and results * too few measurements made so that the not fitting ones could be eliminated, which in fact influenced the results obtained the most * Imprecise clock * Human reaction [�0. ...read more.

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