Lab report
Cellular Respiration Lab
Alcoholic Fermentation (Anaerobic Respiration) in Yeast
Equation for aerobic respiration:
C6H12O6 + 6O2 à 6CO2 + 6H2O + ATP Glucose + Oxygen à Carbon Dioxide + Water + Energy
Equation for alcoholic fermentation (a type of anaerobic respiration):
C6H12O6 à 2C2H5OH + 2CO2 + ATP Glucose à Ethanol + Carbon Dioxide + Energy
Problem: When placed in an enclosed environment with nutrients, will yeast carry out cellular respiration? yes What evidences may be observed to indicate that cellular respiration occurs? With using the example of bread, evidence the cellular resp. occurred is by the bread puffing up. Hypothesis: The balloons will both infate. / Materials: 2 empty water bottles 2 tubes of yeast 1 gram in each tube 40 mL of 20% Glucose solution 40 mL of 20 % Salt solution 2 balloons 2 plastic spoons Gloves *Optional you provide rimmed dish or bowl Procedure:
1. Add the contents of one tube of yeast to one empty water bottle 2. Add the contents of the other tube of yeast to the other empty water bottle 3. Label one bottle with a “G” and the other with a “S” 4. Add the glucose solution to the water bottle with the yeast that is labeled with the “G”. 5. Add the salt solution to the water bottle with the yeast that is labeled with the “S”. 6. Place a balloon over the opening of each water bottle 7. Observe and make predictions. 8. *If your home temperature is cool you may want to consider placing both bottles in a dish of warm (not hot) water.* If you don’t see any activity over the course of the experiment you may want consider this option.
9. Record your observations and take a photograph at 24, 48, and 72 hours after setting up the experiment.
Results:
Glucose Solution Salt Solution
Observations Circumferen ce
in (cm)
Observations Circumference in (cm)
Time 0
nothing
0 Nothing 0
24 hours
Little bit of inflation
2 in nothing 0
48 hours
More inflation from the day before
4 ½ in nothing 0
72 hours
Balloon is very inflated
6 ½ in nothing 0
Photo Time 0:
Photo 24 hours:
Photo 48 hours:
Photo 72 hours:
1. What happened to your each one of the balloons over the course of three days? The bottle with glucose gradually inflated while the one with salt did not 2. Were your results as you expected? If so, say why, and if not say why not. They were not what I expected because I thought they were both going to inflate 3. What is the difference between aerobic and anaerobic respiration? Aerobic respiration takes place in the mitochondria and requires oxygen and glucose, and produces carbon dioxide, water, and energy. Anaerobic respiration also produces energy and uses glucose, but it produces less energy and does not require oxygen. 4. Alcoholic fermentation is used by bakers who make bread. In order to make bread, one must add together flour, sugar, water and yeast. Generally, one kneads the bread dough, covers it and sets it aside in a warm area to allow the bread to “rise.” Considering what you know about alcoholic fermentation, can you provide an explanation for why the bread dough rises? The bread dough rises because gas is being released from the yeast 5. Was there any oxygen present in your flask at the beginning of your experiment? How about at the end of your experiment? In the beginning yes now no 6. Can our cells carry out cellular respiration without oxygen? If so, how? Yes, cellular respiration can occur both aerobically (using oxygen), or anaerobically (without oxygen)