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# An investigation to see whether the concentration of Sucrose effects the amount of Carbon Dioxide released from the respiration in yeast cells

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Introduction

An investigation to see whether the concentration of Sucrose effects the amount of Carbon Dioxide released from the respiration in yeast cells Aim: The aim of this investigation is to discover whether the volume of carbon dioxide released from the respiration of yeast is effected by the concentration of sucrose solution that the yeast uses up as a raw material in it's respiration. Prediction: I predict that as we increase the concentration of the sucrose solution, the quicker the reaction will occur. Also, the greater the concentration the more carbon dioxide will be released, because there will be more sugar in the solution with the greater % and so more raw material which is the limiting factor, this would result in more respiration occurring. I could also predict that if the concentration of the sucrose solution is doubled, the amount of carbon dioxide produced by the larger concentration would be twice as much as the smaller concentration has produced within a given time limit. Hypothesis: When yeast is added to a sugar solution (in this case sucrose) a reaction occurs. This reaction is called fermentation and is widely used throughout industry. Yeast is a living cell and so it respires. This is why the reaction occurs because the yeast is using the simple sugar in the solution to respire on. The process however, is anaerobic respiration because oxygen isn't a raw material in the reaction. Yeast Glucose Alcohol + carbon dioxide (Ethanol) As can be seen above in the word equation the products of the fermentation are ethanol and carbon dioxide. ...read more.

Middle

From observing the graph it is clear to see that all the lines descend this represents a loss in mass. This mass loss should equal the mass of carbon dioxide released from the experiment because the other product is a liquid and so remains in the container and hence will be accounted for when the experiment is massed. The results can also show that as the concentration rises the overall total mass loss increases; this is the case for the 1%, 5%, 10% and 15% sucrose solutions. The mass lost in the experiment using 20% sucrose solution seems to be the same if not less than the mass lost in the experiment using 15% solution. I have drawn on the graph to identify the overall mass loss more easily. The table below shows accurately the exact overall loss in mass. As I said in my analysis of the graph I thought that the biggest overall mass loss might be noticed in the experiment using 15% sucrose solution. Up until the experiment using the 15% solution the overall mass lost rose as can be seen on both the table below and the graph. This suggests that the optimum % sucrose solution for yeast (at the quantity of yeast we used) to respire on is 15. concetration (%) 1 5 10 15 20 complete mass loss (g) 2.6 6.81 12.16 15.2 14.22 For the % solutions lower than 15% it is clear that there was a lower quantity of sugar that the yeast had the potential to respire on. This is because as we can observe if we increased the amount of sugar in the same volume (increased the % of the solution) ...read more.

Conclusion

So it was a suitable procedure that was carried out. I think that the investigation was very reliable and that the results are gathered and interpreted were enough to base my conclusion upon. Maybe to improve the experiment we could put the five separate experiments into the same water bath ensuring that they are all at the same temperature. However in doing this I'm sure the results would be very similar if not exactly the same. As I said earlier I could extend the investigation by investigating the total mass loss when % concentration solutions above 20% are used; to see whether the overall mass loss increases, decreases, or stays the same when the concentration is above the optimum concentration. I would probably predict that the rate of respiration and amount of respiration occurring would be less than in the 15% sucrose solution because I have found out that as the concentration rises above the optimum concentration the rate of reproduction of the yeast cells decreases, so there will be less respiration occurring as there is less yeast cells. I could keep the same concentration and the same amount of yeast and the variable in this investigation could be the pH or the temperature. I would expect a pattern to emerge with the temperature as enzymes that would breakdown the sugar in the solution would denature and so respiration wouldn't be able to occur because glucose won't be present. The pH would also effect the results as different enzymes have different optimum pH's. Also different amounts of a catalyst could be added, however this would be very difficult. Other possibilities could include the variables being different concentration/quantities of yeast, or different types of sugar solutions at the same concentration. Tom Warren Biology coursework Mr Robinson ...read more.

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