The Effect of Sugars on the Respiration by Yeast

The Effect of Sugars on the Respiration by Yeast Introduction A. Purpose: Determine the rate of respiration by yeast while using different sugars, and determine which sugars can be used as a food source by yeast. B. Hypothesis: If glucose is used, then a higher concentration of carbon dioxide during aerobic respiration compared to sucrose, fructose, and lactose. C. Background Research:  Sucrose: A crystalline disaccharide of fructose and glucose, C12H22O11, found in many plants but extracted as ordinary sugar mainly from sugar cane and sugar beets, widely used as a sweetener or preservative and in the manufacture of plastics and soaps  Glucose: A monosaccharide sugar, C6H12O6, occurring widely in most plant and animal tissue. It is the principal circulating sugar in the blood and the major energy source of the body  Fructose: A very sweet sugar, C6H12O6, occurring in many fruits and honey and used as a preservative for foodstuffs and as an intravenous nutrient. Also called fruit sugar  Lactose: A disaccharide, C12H22O11, found in milk, that may be hydrolyzed to yield glucose and galactose Materials and Methods A. Materials used:  LabQuest  LabQuest App  Vernier CO2 Gas Sensor  250 mL respiration chamber  600 mL beaker (for water bath)  5% glucose, sucrose, lactose, and fructose sugar solution  Beral pipets  Hot and cold water  Thermometer  Four 10 X 100 mm test tubes  Yeast suspension  Logger Pro (optional) B. Procedures: 1. Prepare a water bath for the yeast. To prepare the water bath, obtain some warm and cool water from your teacher. Combine the warm and cool water into the 600 mL beaker until it reaches 38-40 degrees Celsius. The beaker should be filled with about 300-400 mL of water. Leave the thermometer in the water during the course of the experiment to monitor the temperature of the water bath 2. Obtain four test tubes and label them G, S, F, and L. 3. Obtain the four sugar solutions: glucose, sucrose, fructose, and lactose. Place 2 mL of the glucose solution in test tube G. Place 2 mL of the sucrose solution in test tube S.

Place 2 mL of the fructose solution in test tube F. Place 2 mL of lactose in test tube L. 4. Place 2 mL of yeast in each of the test tubes. 5. Place the 4 test tubes in the water bath for ten minutes. Make sure you keep the temperature of the water bath between 38 and 40 degrees Celsius. 6. After 10 minutes, take 2 mL of the glucose solution and put in the respiration chamber. 7. Place shaft of CO2 sensor in respiration chamber. 8. After one minute, start LabQuest. Make sure it is set for 300 seconds. When 300 seconds is up, click analyze and then curve fit. Then select linear for the equation and write down the m (slope) for your data table. 9. Clean out respiration chamber with water. Make sure no yeast is in the respiration chamber. 10. Then repeat steps 6-9 for the other 3 sugars. Data Table

Sugar

Rate

Glucose Sucrose Fructose Lactose

4.9035 7.4336 9.3044 3.6225