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'Factors affecting the rate of respiration in immobilised yeast'.

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Biology Coursework James Wyatt 'Factors affecting the rate of respiration in immobilised yeast' Variables The input variable that we will be investigating will be the temperature of the glucose solution that the yeast ball rises quickest in. This will be measured at regular intervals. The output variable is the time taken for the yeast balls to respire and rise to the top of the glucose solution. They will respire by the carbon dioxide from the solution entering the yeast balls, causing them to rise. The variables that will be controlled and kept the same are the volume of water, the amount of glucose, the concentration of the glucose and the size and mass of the beads. All of these will be controlled to keep a fair test. We will try and keep the beads the same size although it may be little tricky. Should this not be kept identically, it should not affect the results in a drastic way. If there was more glucose in one solution than another then there would be and unfair test and there would be more carbon dioxide to respire. ...read more.


This will then be placed into the beaker of water and then five yeast balls will be weighed and added. We will try and keep the weight and mass of the yeast balls the same. Once the yeast balls are added the stopwatch will be started and we will wait until the yeast balls rise. We will repeat this for each different temperature and then we will do each temperature again one more time in case of incorrect results and to make sure we can get the most accurate possible answer. In our experiment we will use 45 Yeast balls (five for each different temperature and one repeats), a boiling tube, a 250 cm beaker, 50ml of water, 20 cm of 10% glucose solution, a kettle, a thermometer and a stopwatch. Here is a diagram of our equipment: Preliminary Work We did some experiments at the start using 8% concentration of glucose. We did temperatures 25�, 30� and 35�. We waited for a long time on all three in experiments and did not get any results. The yeast balls didn't rise. ...read more.


The results are pretty accurate as we did our experiment once and then repeated it to check for accuracy. The results each time were almost the same as before, with not much difference. Most other groups had the same patterns as us, although some used different concentrations of glucose solution than us. There were no real anomalies obvious on the graph or in our results as the point are quite close to the curve on the graphs. I think that if we was to do the experiment again, I would investigate using other concentrations of glucose solution to see how the results compared to that of 10% concentration. To improve the experiment I would do the experiment in a water bath with a thermostat. I would need to make the mass and size of the yeast balls more exact and regular in reliability and accurateness. When taking results next time I would use closer intervals between each temperature. I would also investigate whether the amount of water of glucose solution made much of a difference to our experiment. I could also investigate more temperatures around the 40� mark so I could find what the optimum temperature is for this particular experiment. Overall I think that my results and graph support my conclusion. ...read more.

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