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# Investigating respiration in yeast.

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Introduction

Investigating respiration in yeast I am investigating the respiration of yeast and finding the best conditions for producing carbon dioxide by breaking down glucose using yeast as the catalyst. Affecting factors There are factors that could affect the outcome of my investigation such as: > The temperature > The amount of yeast > Another factor that could affect our investigation is the percentage of glucose in the yeast. Fair test To make my investigation a fair test. I will use the same apparatus each time but washing and drying them out thoroughly so not substances from the previous experiments will be left. I will use as accurately as possible the same amount of glucose and yeast each time and using the same concentration. I must also make sure to leave all experiments undisturbed during the course of respiring, this means they cannot be stirred or let air get to them. I have chosen to investigate the affect the % concentration of glucose has on the rate of respiration in yeast as a preliminary experiment to find out which concentration will be the best to use. I will use an experiment to determine whether the yeast�s rate of respiration will be quicker, slower or if it does not change when the concentration of glucose is varied. ...read more.

Middle

Then put the beaker in a water bath at 30oC then I will time the bubbles. I will time for 5minutes, then observe which test tube had produced the most bubbles. My results were as follows: Glucose Concentration (g/l) How many bubble produced 1g/l None 10g/l Not a lot 25g/l Few 50g/l Some 100g/l Lots 200g/l Quite a few The best concentration is 100g/l. So I shall use this concentration in my main experiment. Main Experiment method: I will use a syringe to get 3ml of yeast suspension and 3ml of glucose solution. I will then put the capillary tube on the end of the syringe, then I will get a beaker and fill it almost full of the which ever temperature water I was varying for that particular experiment and then place the syringe into the beaker. Then make sure the capillary tube is horizontal (by resting it on an upside beaker maybe). I will then mark on the capillary tube where the bubble started, start the stopwatch, after 1min I will mark on where the bubble ended up at then work out how far the bubbles had traveled. My range of results will be from 20oC to 60oC and I will repeat each experiment 3 times then find the average. ...read more.

Conclusion

Evaluation My results are as accurate and reliable as possible. No major anomalies were shown. But in the end I did the experiment on the computer so it was always a fair test. I made sure that the temperature was as accurate as it could have been at all times by constantly checking with a thermometer, I kept the capillary tube horizontal throughout so that the bubble wouldn't be put to neither a advantage nor disadvantage. I also used the same equipment throughout and used the same amount of yeast suspension and glucose solution. Several things which could have been improved. These are that I could have investigated a broader range or results, instead of 20oC to 60oC, next time I would do from 10oC to 80oC, instead of going up in steps of 10oC I would go up in 5oC which would make much more accurate. To improve accuracy you could use a digital thermometer so you would always have an accurate temperature in contrast to mercury thermometers which can be inaccurate. On the hole I think that this experiment was a success as we did it on the computers in the end and not much can go wrong if we do it on there. But next time maybe a few more pilot test and other small tests, maybe a different method could get better results. ...read more.

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