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Anaerobic Yeast Respiration

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AT1 GCSE Practical Assessment Anaerobic Yeast Respiration Aim The aim of our experiment was to investigate one possible factor which could affect the rate of yeast respiration. Preliminary Work To provide an insight into our investigation, we researched some preliminary work which has previously been done. The preliminary researchers had altered both the temperature of the yeast, and the concentration of the glucose in the yeast. This was beneficial to our experiment because we could clearly see which of these two variants would give us the more interesting and fruitful experiment. The results of these preliminary experiments can be observed below: Temperature Of Yeast (�C) Concentration of Glucose (ml) Time Left Respiring (minutes) CO2 Produced (ml) Control 21.0 1.5 5.0 2.0 Increased Glucose 21.0 2.0 5.0 0.5 Increased Temperature 35.0 1.5 5.0 6.2 From this table, we can clearly see that varying temperature will create more varied results. The more varied the results, the more we will be able to document in this write-up. From this preliminary work, we have decided to focus our experiment on alterations to the temperature. Prediction And Scientific Knowledge Our prediction is that as the temperature increases, the amount of yeast respiration occurring will also increase (hence the more carbon dioxide we will witness being given off). ...read more.


A rubber bung with glass delivery tubing poking through it will be placed over the boiling tube to assure that all carbon dioxide is passed through the small network of pipes which lead into an upturned measuring cylinder which is clamped to another retort stand. Underneath the boiling tube is a beaker of hot or cold water, which will be used as a water bath to alter the yeast solution's temperature. The measuring cylinder is filled with water and placed upside-down in a tub of water. This allows the carbon dioxide to flow directly from the yeast, through the piping, into the measuring cylinder. 15ml of yeast was used in the boiling tube, and the beaker and tub were filled so that their contents would be submerged. We have decided to repeat the experiment three times for each quantity, and then calculate an average of these results. This will give us the most accurate results, which is what we want. We are going to count how many millilitres of carbon dioxide have been produced at the bottom of the measuring cylinder. This will simply and clearly tell us how much respiration has been done. ...read more.


In my prediction I stated that as the temperature of the water bath surrounding the yeast solution increases, the amount of carbon dioxide produced (and therefore the amount of respiration that has occurred) would do the same. This was proven correct by my experiment. At the lowest temperature (10�), an average of only 0.7ml of carbon dioxide was produced, whereas at the other end of the scale, 60�, a 5.3ml average was obtained. Evaluation Our experiment was in some ways very accurate and in other ways not very accurate at all. We carried out all pars of the experiment with the same apparatus, but we changed the yeast solution halfway through which somewhat soured our results. Asides from this imperfection, the rest of our experiment was as fair as we could have made it. The experiment could have been carried out at higher and lower temperatures to produce a more accurate graph. I could have carried out each of the same temperatures more than three times. I could have not left a one-hour lunch-break in the middle, which was the main cause of the anomalous results I had. My experiment showed what could change the rate of yeast respiration, and so it was a success. Luke Charman 11TA - Candidate 7074 - Centre 17243 01/05/2007 05:33:45 ...read more.

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This is a well written report the covers the necessary aspects.
1.The report is well structured by the subheadings.
2. Background knowledge needs to be referenced.
3. The conclusion uses data well but the pattern needs to be explained.
4. The evaluation is very brief and does not suggest further investigations.

Marked by teacher Luke Smithen 16/07/2013

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