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What is the effect on the rate of respiration of yeast cells with glucose when the temperature is varied?

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Biology Coursework Planning Problem What is the effect on the rate of respiration of yeast cells with glucose when the temperature is varied? Aim The aim of the experiment is to investigate the effect of temperature on the rate of respiration of yeast cells with glucose. As yeast cells use up glucose in respiration, carbon dioxide gas is given off. Measurements of the volume of carbon dioxide gas given off within a set amount of time can be used to measure the rate of reaction. A fast rate of reaction would be indicated by a large volume of carbon dioxide gas being collected within this set amount of time. A small volume of carbon dioxide gas collected within the same amount of time would indicate a slower rate of reaction. The rate of reaction will be fastest at the optimum temperature for working enzymes in yeast cells. Procedure for preliminary experiment List of apparatus A packet of fast acting yeast A tub of D-glucose Distilled water A spatula A rapid weighing balance A 100ml measuring cylinder A conical flask A count down timer A gas syringe A delivery tube with rubber bungs tightly fitted at the ends joined to the gas syringe 2 clamp stands An electrical water bath Method The equipment above was collected and set up as shown below and the electrical water bath was set to 20�C: * 25g of yeast and 12.5g of glucose were measured out into a 100ml beaker using a weighing balance. * Using a measuring cylinder, 50ml of distilled water at room temperature was measured. * Pour this into the beaker of yeast and glucose. * Dissolve the yeast, glucose and water together by stirring with a glass rod. * Pour this solution into the conical flask in the water bath. * Place the rubber bung on the top of the conical flask, making sure that it is tightly fitted. ...read more.


Restart the timer. When this time is up measure and record the amount of gas produced. Continue this until 20 minutes has elapsed. * Pour out the yeast suspension in the conical flask and rinse it out twice with tap water and 3 times with distilled water. * Repeat steps 2-6 for the next 2 experiments ensuring that the temperature remains constant throughout. * For experiments at different temperatures repeat the whole procedure. * Allow time for the solution to adjust to the temperature of the water bath. Choice of apparatus and reasons why Item What it is used for Reason for choice 100ml measuring cylinder To measure out appropriate volume of solution needed. It is easy to use and allows accurate measurements to be taken. 100ml beakers Containing mixtures of dry yeast and glucose which will be dissolved in water. They can be handled with ease and minimum difficulty. It is large enough in size to hold the required amount of solution. 250ml beakers To hold large volumes of water. It is large enough to allow hot water from the kettle to be poured into it. Conical flask To contain yeast and glucose solutions. It is the appropriate size for holding the volume of gas produced. The rubber bung at the top of the conical flask means that any gas leaks are minimal, so results are undistorted and valid. Spatulas Measuring out the correct masses of yeast and glucose and stirring the solution made when water is added. It is easy to handle as it is light in weight. Due to its small size it is ideal for small quantities to be taken when measuring specific masses. The same type of spatula was used to stir the yeast solution throughout the experiment. This ensured a fair test. Electrical water bath Provides and maintains an environment with a constant temperature. It is easy to use and effective at maintaining a constant temperature. ...read more.


However, the conclusions made as a whole were valid but there are still some uncertainties associated with some of the anomalous results. � The number of times that I shake the test tube. (This has to be controlled because the shacking of the test tube activates the yeast. If I shake the yeast it becomes more active thus it will give off more hydrogen, which will affect the time taken for the colour of the TTC to change. I will control this by shacking the test tube before the experiment and every 60 seconds by placing the bung on the test tube and shake it 10 times by turning it upside down. I will then remove the rubber bung). � The batch of yeast (This has to be controlled because different yeast batches have different activities. This will affect my experiment because if 1 batch of yeast was active then rate of reaction would be faster and if another batch was not very active then my rate of reaction will be slow giving me inaccurate results. I will control this by trying to complete my experiment in one lesson so I can use the same yeast each time). We had to keep the beaker rapped in tin foil so that the temperature would stay as close as possible to the temperature that we were measuring. The tin foil acts as an insulator and keeps the heat inside the water. the same thermometer during the whole experiment the results would be inaccurate, as I would have to wait for the thermometer to reach the certain temperatures again. I made sure that I used the same amounts of yeast accurately, so that I could get the most accurate results. Upon looking back at the adjustments made, I believe that I am confident in saying that, I made sure that my experiment was as fair as I could possibly make it. ?? ?? ?? ?? Filmawit Kiros - 1 - ...read more.

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