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Investigate one factor that affects the rate of respiration of yeast

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Biology Coursework Investigate one factor that affects the rate of respiration of yeast Plan Aim: In my experiment, my aim is to find out any correlation between the rate of respiration of yeast and the concentration of glucose in the yeast. I shall do this by conducing an experiment which will involves a steady increment of glucose and for each increment, I will measure the temperature to see whether if it increases and the rate of increment. There are many factors (variables) that could affect this investigation such as the temperature the yeast respires at as at different temperatures the enzymes in yeast work faster or slower at breaking down the glucose. The amount of yeast will also have an effect on the results, if we are to use different amounts in each experiment it will form an unfair test. I must also make sure to leave all experiment 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 rate of respiration in yeast. I will use an experiment to determine whether the yeast's rate of respiration will increase, decrease or if it will stay constant even when the % concentration of glucose in it is varied. Prediction: I predict that the yeast's respiration rate of reaction should increase in speed as the % of glucose increases. ...read more.


and the amount of glucose with a measuring cylinder (precise to �0.5ml) Apparatus: Yeast, glucose solution (with different concentrations), boiling tube, 250ml beaker, gas syringe, boss, clamp, stand, boiling tube rack, electrical balance, 2x measuring cylinder, spatula, delivery tube with rubber bung, cotton wool Diagram: Method: 1. Firstly collect all apparatus and set up like the diagram on the previous page. 2. Pour the 10% yeast solution and measure 10ml using measuring cylinder. 3. Measure 10ml of glucose solution (2% - initial) using measuring cylinder. 4. Pour the 10ml of 10% yeast solution into a boiling tube. 5. Reset the gas syringe if needed (moving it back to 0 ml). 6. Pour some hot water (amount doesn't matter) into a beaker. 7. Use a thermometer and check the temperature. If it is less than 40oC, add more hot water, if it is more than 40oC, pour out some hot water or add more tap water. 8. Put the 10ml of glucose solution and mix well using glass rod for 10 seconds 9. Immediately connect it to the gas syringe. 10. Start the stop watch and wait for 2 minutes. 11. When 2 minutes is reached, stop the stopwatch and record results (the volume of gas produced) in a table. 12. Repeat step 2-8 but with different concentrations of glucose (2%, 4%, 6% and 8, 10% concentration). Pretest: I started off using 10% yeast solution and 10% glucose solution (10ml). ...read more.


Although the inaccuracies are very small, it can still affect a little to the ending result. I could use the measuring cylinders with 0.1ml markings to measure the volumes so it is more precise. However, I would like to obtain more results, using higher concentrations of glucose. This is because I did only up to 10% concentration of glucose solution, which is very low. Therefore, the graph drawn didn't represent a full picture of the experiment, which if did, might conflict with my prediction. Although all results up to 10% concentration of glucose did agree with my prediction, but that doesn't mean if the glucose concentration is 70% it will still agree with my prediction, which is what I want to understand fully and investigate about. On the other hand I didn't have enough time to do so many readings. So if there was an extension in time for me to obtain more results, I could most probably give a stronger evidence for my prediction or prove it wrong. Possible Extensions: 1. Investigate the best pH for the yeast enzymes to work the fastest rate in. 2. Investigate the best temperature the yeast enzymes work at the fastest rate in. 3. Investigate the rate of respiration of yeast when the variable is the concentration of yeast. 4. Investigate whether a change in concentration of glucose or a change in concentration of yeast will affect the respiration of yeast the most. ?? ?? ?? ?? Isaac Wong 11H Biology ...read more.

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