When oxygen level depletes yeast functions anaerobically and then carries out Ethanol Fermentation. Fermentation in brewer’s yeast is used in industries to manufacture baked good and alcoholic beverages. Depending on the substance being fermented the variety of Yeast being used, and carbon dioxide availability produced during the process yeast fermentation may be used to produce different substances like wine, champagne, syrupy drinks and ciders.
Ethanol Fermentation in the yeast cells can occur in the cytoplasm via enzymes under anaerobic conditions using the chemical reaction below:
C12H22O11(s) + H2O → CH3CH2OH(l) + 4 + ATP
Sucrose + Water → Ethanol + Carbon Dioxide + ATP (energy)
Research Question:
How does the surrounding temperature affect the amount of Carbon Dioxide (CO2) produced in the cellular respiration in yeast during anaerobic reaction?
Hypothesis:
The Kinetic Energy Theory states that the rate of a reaction will increase with in an increase in the temperature. This is due to the increase in the speed of the particles, brought about by the extra energy given to them by increase in temperature. The faster particles will bring about more particle collisions and the reaction will take place faster. Anaerobic respiration is controlled by a series of enzymes which are sensitive to temperature change, so the whole process responds to changes in temperature. As the temperature increases the rate of reaction increases until you reach an optimum temperature (BBC Home).
Variables:
Manipulated variable is the variable that the experimenter decides to change to see if there is or there is no effect on the experiment. For that reason temperature was taken as a manipulated variable which is manipulated by the experimenter.
The responding variable is the variable that will change as a result of the change in the manipulated variable. It may also be observed and or measured to determine the quantity or quality of change. One of the products of the anaerobic reaction will be Carbon Dioxide, so it is valid to find the amount of Carbon Dioxide (CO2) produced from the reaction to find ATP.
Several variables which could affect the dependent variable were controlled. Same amount of yeast taken and the yeast were provided with same amount of sucrose. All the samples are put in the same amount of test tube. It is not easy to get a vacuum or a space in which experimenter can make the yeast to perform anaerobic reaction. In order to prevent the wrong results, all the experiments should be started at the same time.
All the samples of yeast should be taken by the same person in order to prevent the wrong scale. All the yeast taken would be from the same place so that we get the same species of yeast. Health of the yeast cells should be fairly similar. They both should be healthy in terms of producing ATP. Same and good quality of test tubes and water tubes should be taken in order to prevent the breaking and tearing respectively. Time is the biggest controlled variable, which has to control to get the amount of carbon dioxide. Pressure is maintained throughout the lab. Same kinds of rubber knobs are used.
Design:
ATP and CO2 are both the products of cellular respiration. It is not easy to find the amount of ATP produced during cellular respiration. So measuring the amount of carbon dioxide produced during anaerobic respiration will indirectly allow the experimenter to find the amount of ATP produced by the yeast cell. Samples of the yeast will be taken from the same location. Sucrose will be added to them and will be kept in different temperature for a particular time. Carbon dioxide will be collected in the water tube and the volume of carbon dioxide will be found with the Ideal gas law.
Materials required:
In order to complete the experiment some materials are required. Safety goggles, apron and oxygen mask for safety. To take the yeast samples tongs are required, along with the scoopula. Electronic balance scale is required to find the weight of different objects. Along with that five 100 ml test tubes, 5 rubber knobs, 5 heating apparatuses and 5 water tubes are required. A calculator is required to do all the complex calculations. Yeast and sucrose are required by the experimenter to start the experiment. A big 2 liter bucket with stopper and tube attached to it. Some water in a beaker is required. Test tube holder and tongs are required to carry or move test tubes from one place to another. Timer is required as time is one of the biggest controlled variables.
Procedure:
Clean all the test tubes, distillation flasks and scoopulas with distilled water
Take 5 samples of yeast each measuring 5 g from the same location. Put all the samples in 5 different test tubes, each test tube measuring 100 ml. Mark the test tubes from 1 to 5. Measure 2 grams of sucrose with the electronic balance scale and add the sucrose to the test tubes with the help of a scoopula in the test tubes at the same time. Set a timer for 4 hours. Keep the test tubes in the beaker as shown in the figure with a stopper on the end and a pipe in the stopper and start the timer. All the Carbon Dioxide produced from aerobic respiration will be passed through the tube into the water and then into the atmosphere. The tube would not let any air come in the beaker. According to the research done, under normal circumstances it would take 4 hours for the yeast to take up the oxygen present in the beaker.
In them mean time set up 5 heating apparatuses for heating the test tube. Set up the temperature of the first burner at 25° C and keep on adding 5° C for the next burner so that the maximum temperature reach would be equal to 45° C. And mark the apparatuses from 1 to 5. After 4 hours take the test tubes out of the beaker with the help of the test tube tongs and immediately put the empty water tube on top of the test tube. There will be some loss of carbon dioxide but it will be same for all. Put the test tubes in their respective test tube holders in the apparatus at the same time. Keep the test tubes on the apparatus for 4 hours.
Close the water tube and measure the total mass of the water tube. Calculate the mass of carbon dioxide by subtracting the mass of the empty water tube from the mass of the water tube with carbon dioxide. Write down the results in a chart. The molar mass of CO2 is 44.01g/mole. Calculate the number of moles by dividing the mass of carbon dioxide by the molar mass.
The main and the accurate way to find the amount of CO2 produce is by Ideal gas law. The formula for Ideal gas law is PV=NRT. For our values P is the pressure at STP and it is 101.325. R is the universal gas law constant which is 8.3145 m3·Pa/(mol·K). T is the temperature of the oven or the temperature at which respiration was happening. N is amount of substance, in mol and which is calculated by dividing the mass of carbon dioxide by the molar mass of carbon dioxide. After calculating the number of moles substitute the values of P, N, R and T and solve for V. By this experimenter would be able to find the volumes at different temperatures. The amount of carbon dioxide will indirectly tell experimenter the amount of ATP.
Sources
"BBC - Education Scotland - Standard Grade Bitesize Revision - Ask a Teacher - Biology - Biotechnology - Question From ." BBC - Homepage. 10 Nov. 2008 <http://www.bbc.co.uk/scotland/education/bitesize/standard/other/sos/biology/biotechnology/biotechnology_16.shtml>.
Papers - The Effect of Temperature on the Respiration of Yeast." Search Essays -- Free Essays and Term Papers. 9 Nov. 2008 <http://www.123helpme.com/view.asp?id=122462>.
Inquiry into BIOLOGY. Ontario: Keith Owen Richards, 2007.
