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Rate of respiration in Yeast.

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Introduction

Aim: I am going to investigate the rate of respiration of yeast cells in the presence of two different sugar solutions: glucose, sucrose. I will examine the two solutions seeing which one makes the yeast respire faster. I will be able to tell which sugar solution is faster at making the yeast respire by counting the number of bubbles passed through 20cm of water after the yeast and glucose solutions have been mixed. Prediction: I predict that the glucose solution will provide the yeast with a better medium by which it will produce a faster rate of respiration. This is because glucose is the simplest type of carbohydrate (monosaccharide). However sucrose is a complex sugar it contains large molecules making it a disaccharide. Due to the large molecules being saturated and the small molecules being unsaturated this will allow the glucose to mix easily with the yeast therefore making it respire more frequently. The sucrose sugar however having larger molecules will find it harder to mix in with the yeast; this will make the rate of respiration in the sucrose much slower as it is not as efficient as the glucose. ...read more.

Middle

In another test tube I will place 15 cm of water. Into this test tube I will place the other end of the delivery tube. I will start the stopwatch and begin counting the number of bubbles that come through into the water. If no bubbles appear then I will gently shake the test tube full of yeast and sugar this may allow any blockages in the delivery tube to clear and we will be able to see if any bubbles form in the water. After two minutes are over I will record the number of bubbles that appeared and record on a sheet of paper. I will dispose of the contents of the test tubes and replace them with new ones. I will repeat the test for both the glucose and sucrose five times in the same manner. Method: After collecting all of my equipment and setting it up. I measured out 3cm of yeast and placed it inside a test tube. To this I added 5cm of glucose solution. I allowed it to heat inside a beaker full of warm water which was at 45 degrees Celsius. After leaving the test tube in there for 1 minute I collected another test tube and inside it I placed 15cm of water. ...read more.

Conclusion

I received no anomalous results. We should have had another sugar to use as we could have compared it to the glucose and sucrose and this would have provided us with better results. I think that there was enough evidence to draw a conclusion however if we had used another type of sugar it would have made the evidence much more precise and clearer. I don't think that my method could have been improved in any way unless another sugar was utilized. There were some things that were difficult to keep constant in the experiment and this is where my results may have wavered slightly. It was difficult to keep the temperature of the warm water constant as it dipped at times which could have had an effect on how efficient the enzymes were. The delivery tubes were becoming blocked sometimes and by shaking the test tube it cleared them. However as we shook the test tube a large number of bubbles were formed which may not have formed if we didn't shake the test tube. Also we might have been shaking the test tubes at different speed which may have caused a greater number of bubbles to be released. Overall I felt that the experiment was accurate and reliable and there was not much that could have been changed on it. By Omar Jamshad 10S ...read more.

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