Investigation of the effect of glucose concentration on anaerobic respiration in yeast.

Prediction: I predict that the conical flask with the yeast and the most glucose concentration will respire quickest.

The conical flask with the yeast and the least glucose concentration will respire slowest. This is because of the Lock and Key Theory. Enzymes basically work due to the 'lock and key' theory, where the substrate (the ‘key’) fits into the active site on the enzyme and they bind together, the reaction takes place and the substrate unlocks to form one or more new substances leaving the enzyme ready to perform the binding again. An enzyme can only bind with a substrate that fits the shape of the active site unique to that kind of enzyme. When some substrate substances induce a fit with the enzyme, the enzyme may not be able to 'accept' some other substrates.

Results Table:

Safety Points:

1. Make sure all glassware is away from edge of table.
2. Put all Coats, Bags & Stools away.
3. Make sure water bath doesn’t get too hot.
4. Always wash hands when finish.
5. Take care of all the glassware.

Analysis:

From my final results table, I can use the average results to plot a graph of results.

From my results I can identify a line of best fit. My graph shows that as the concentration of glucose solution is increased, the amount of carbon dioxide produced also increases. The fact that carbon dioxide is being produced, proves that respiration is taking place. The continual increase of carbon dioxide means that the rate of respiration increases as the concentration becomes less dilute and stronger. I can see that the rate of respiration is at its slowest when there is little glucose solution present. When the concentration was of 10%, the amount of bubbles produced isn’t very high at an average of 27 in 5 min. There is a big difference between the rates of reaction of 10% compared with the 30% concentrations. This definitely suggests that concentration has a large impacting affect on the rate of respiration. The concentration of a solution can speed up or slow down the rate of respiration depending on how concentrated the solution is. In the case of my experiment, the strongest concentration speeded up the rate of respiration while the weakest concentration was very slow in producing carbon dioxide thus, showing that the rate of respiration was much slower.

Evaluation:

I thought the results obtained were quite accurate. They seem to be in the same sort of shape on my graph. However, on my repeats there are some noticeable differences between test 2 and the others. On test 2 for 20%, the result is 10 and 12 bubbles less than test 1 & 3 and this happens again for 25%, it is 11 and 15 bubbles less than test 1 & 3. The explanation I can offer for this is that there must have been a mistake I have made or I might have not let it rest for the allotted time. I thought all of my other results generally fitted the overall trend well. I thought the experiment allowed the prediction to be tested very well as it proved the points that I wanted it to, and very conclusively as well. I thought my method was pretty foolproof too which would help anyone who wanted to do this experiment and only had my piece of coursework. I think my results were reliable enough to support the prediction especially due to the fact that there are no obvious abnormalities. If I was to do the experiment again, I would use a different means of counting the bubbles as the human eye could make mistakes.