Introduction Yeast is a single celled fungus. It respires anaerobically (the release of energy from glucose, without combining it with oxygen). When this is done it converts sugar to ethanol. Yeast is one of the living cells which can respire without oxygen anaerobically by reacting with a sugar solution such as glucose to produce carbon dioxide and ethanol and a small amount of energy. When the conversion of sugar to ethanol and carbon dioxide it is known as fermentation. The energy formed is necessary for the yeast to carry out the reactions necessary for cell growth. Yeast cell replicates fastest at about forty-two degrees Celsius.
The variable I have used to carry out this experiment is Temperature Equation: Glucose -> alcohol + carbon dioxide + energy Prediction I predict that in my bubble count the number of bubbles will increase gradually as the temperature increase up to sixty-two degrees Celsius because the yeast will respire faster at a higher temperature. At 27 degrees Celsius the yeast will give off Carbon dioxide because the temperature is to low and it is not high enough to form a reaction but between 32 degrees Celsius and 47 degrees Celsius a large amount of Carbon Dioxide we be given off.
The number of bubbles made will decrease when the temperature is higher then fifty degrees Celsius because the heat from the water will start to denature the yeast cells. I think that once the temperature has raised over sixty degrees Celsius no bubbles will be produced because the water will be to hot for the yeast, therefore the heat from the water will denature the yeast and no respiration will able to take place. Preliminary Test The quantities of materials I have used are: 100cm3 of cold water, 50cm3 of kettle water 10% glucose 10% yeast.
The glucose solution and the yeast solution used are fully concentrated. I timed the amount of oxygen gas coming out of the Boiling Tube and through the delivery tube and out of the test tube, forming bubbles for 1minute. I repeated this 3 times and my results show that the amount of bubbles has risen. I will measure the rate of respiration in yeast by counting the number of bubbles produced within one minute at different temperatures. I will make sure the yeast and glucose solution has been left for at least ten minutes to settle to the temperature before starting to count the bubbles.
The amount of yeast will be kept the same as the amount of glucose, 10cm3 of yeast and 10cm3 of glucose. The only thing that will change is the temperature. The temperature range I have used ranges from 27 degrees Celsius to 47 degrees Celsius. Outline Plan Fair Testing Fair testing is that you make sure that all substances are out in with the same amount. To do a fair test for this experiment you must have these substances listed below at the same amount: Same amount of suspension of yeast in cooled, boiled Glucose solution. 10% yeast.
10% glucose In the beaker a water bath of 37 degrees Celsius is needed. The boiling tube is then inserted into the beaker. Range of Measurements The method I am going to use is bubble count 100cm3 of cold water, 50cm3 of kettle water 10% glucose 10% yeast Accuracy I will repeat each measurement at least 3 times Safety To make sure that the kettle of water does not get knocked over and make sure that water does not spill on the Electricity List of Apparatus Test Tube Delivery tube Beaker Boiling tube Stop clock Measuring cylinder Detailed Method.
1. Firstly you pour 10% of Yeast solution from the beaker into the measuring cylinder. 2. You then poured the Yeast solution from the measuring cylinder into the delivery tube. 3. Next I Pour 10% of Glucose solution from the beaker into the measuring cylinder. 4. Then you pour the Glucose solution from the measuring cylinder into the delivery tube. 5. Once you have done that you pour 5% of water into the test tube 6. Next you create a water bath using 100cm3 of tap water and 25cm3 of boiling kettle water to form 27degrees Celsius. 7.
After that you connect the delivery tube to the boiling tube with the rubber bung going into the boiling tube and the glass end going into a test tube. 8. You then start your stop clock and leave it running for 10minutes waiting for the yeast and glucose solution to react and form carbon dioxide which should then form bubbles. 9. You then count the amount of bubbles formed within one minute. 10. When you have completed those following steps you repeated them three times for each temperature. You use these eight different temperatures which are: 27, 32, 37, 42, 47, 52, 57, & 62 degrees Celsius.
Diagram to show the method used Results Temperature (degrees Celsius) Carbon Dioxide Bubbles within one minute 1 2 3 Average No Bubbles formed 0 Conclusion Hydrogen Peroxide is broken down by peroxides in many organisms. Its catalytic results in the release of oxygen gas can be collected and is measured. The estimation of the oxygen release can be made by counting bubbles. Equation: 2H2O2 –> 2H2O + O2 Hydrogen Peroxide.