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An Investigation into how the anaerobic respiration of glucose and yeast is effected by temperature

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Introduction

An Investigation into how the anaerobic respiration of glucose and yeast is effected by temperature AIM: To investigate exactly how temperature effects the anaerobic respiration of yeast and glucose mixture EQUIPMENT: * Water bath filled almost to the top with water (this must be full so the entire syringe is submerged and therefore at a constant temperature, for the even anaerobic respiration of yeast and glucose mixture) * 10ml syringe * Three 5ml portions of glucose and yeast mixture containing 2.5ml of each substance * Thermometer * Kettle * Stopwatch * Measuring cylinder METHOD: 1) Gather together all equipment 2) Fill the syringe with the glucose and yeast mixture. 3) Put water into the water bath, straight from the tap and then set up the equipment like so, making sure the measuring cylinder is full to its top measure (with a small air gap at the top), and securely fixed to the side of the water bath: 4) Wait until the temperature of the water is 25�c and then place the syringe in the water and leave it for one minute. Make sure the hole at the end of the syringe is inside the measuring cylinder. During this time make sure the temperature is maintained at 25�c. This is because in this experiment, the temperature is the variable, and it must be constant for its separate measures. 5) Start the stopwatch from the first bubble emitted from the syringe. ...read more.

Middle

From that point onwards, the substrate and the enzyme can no longer react and henceforth the substrate will not be broken down. The formula for anaerobic respiration is: zymase ( enzyme) glucose ethanol + carbon dioxide + energy It can be seen that the enzyme, zymase is the catalyst in the reaction and when it has been denatured, it cannot function, and hence the anaerobic respiration will occur very slightly, or not at all. All enzymes are complex biological molecules and are very precise in the area of temperature that they will function at. It is known for a fact that pepsin is denatured at 40�c. Henceforth, it is believed that, like pepsin (another enzyme), zymase will be denatured at around 40�c and hence will not be able to break down the glucose in such high temperatures. It is believed that the zymase will be denatured at 40�c, as many enzymes have similar properties as they are molecularly constructed in similar fashions. This temperature is just above the body temperature of many mammals and is hence the temperature at which it is thought that ensures the enzyme will work most effectively, when it is needed, in the body of a mammal. Because heat speeds up reactions, it is predicted that yeast will perform anaerobic respiration with glucose, the higher the temperature, until 40�c, at which point the zymase will be denatured. Once the zymase has been denatured, the rate of anaerobic respiration will drop rapidly, as the active site is no longer usable. ...read more.

Conclusion

The procedure used was very efficient. We made sure that it was a fair test because we kept the temperature, the amount of mixture and the time span all the same and did several repetitions to ensure the results were constant and not random. The measuring procedure was also accurate as we used a measuring cylinder to measure the carbon dioxide produced, this was preferable to counting the bubbles produced, which could be inaccurate and more difficult to measure. We encountered some problems of manual nature however; it was hard to keep the measuring cylinder stuck to the side of the water bath, as the cellotape became unsticky as soon as it became wet. Therefore if the experiment was to be done again a few changes could be made. For example, we could use a clamp stand to hold the cylinder instead of sticky tape. Also, due to time constrictions, the temperature at which zymase actually denatures was not found. It would be better if more time were available so that the temperature at which zymase was denatured could be found. Another experiment that could be done to further test this experiment would be to use the variable of the ratio of yeast to glucose, and what the results are when this is changed. The combination of such subsequent experiments along with the one explored in this investigation, could be used to build up an accurate conclusion as to the best conditions for yeast and glucose mixture to perform anaerobic respiration. Tom Stringer 1 ...read more.

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