Risk Assessment
There were a few risks associated with the experiment. When using the kettle, we needed to be sure not to burn ourselves. The boiling water could of potentially caused a serious burn injury or a hazard if on the floor. Also, we needed to make sure all glass beakers were securely on the desk to avoid any shattering.
Method
We will start by using 50ml of water. We will use water of different temperatures. We will pour water form the kettle into the beaker and add cold water from the tap to get to the right temperature. We will then put 20cm of glucose solution with 10% concentration into a boiling tube. 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. We therefore changed our concentration from 8% to 10%. This would have been because of a lack of carbon dioxide and therefore the yeast balls would not of risen.
Analysis
The results from the table show there is a steady increase in the rate of respiration and a decrease in the time for the yeast balls to rise until the temperature reaches 50°C. This was the optimum temperature and from this point onwards the amount of respiration in the yeast decreased, causing the yeast balls to take longer to rise. This suggests that the enzymes have begun to denature because the lock and key mechanism broke down where the enzymes could no longer come into so much contact with the substrate glucose. My prediction was fairly accurate in the sense I thought that there would be a point at which the yeast would rise quickest at and there after that point, the yeast would take longer to rise. There were many reasons why the time for the yeast balls to rise decreased and the rate of respiration increased. The time for the yeast balls to rise decreased and the rate of respiration increased because as the particles moved quicker, the rate of collision between the glucose and yeast increased. Therefore the glucose diffused more quickly in the yeast ball and the rate of respiration increased.
Evaluation
I think that we carried out the fairest test possible, keeping our results accurate and reliable. My prediction was correct in that I thought that there would come a point where the yeast balls would not rise any quicker and the rate of respiration would decrease at this point. We found that the temperature of the water was hard to control as it was constantly cooling during each experiment. We therefore needed to keep adding hot water, making sure we didn’t put too much water in. 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.
