Download Respiration Lab. eScience Lab 8. Experiments 1 and 2. Tips

Respiration Lab. eScience Lab 8. Experiments 1 and 2. Tips and Questions to
Answer.
Tip 1: There is a lab demonstration video for each experiment. You should watch them before
starting.
Tip 2: The temperature conditions for the yeast are extremely important. If your temperature is too
low they will be very slow and you will not get results. If the temperature is too high you will kill your
yeast and will not get results!
Tip 3: You will need to allow extra time for experiment 2 of this lab. There are beans that need to soak
for 24 hours. After this, you need a 3 hour period to observe the experiment. Finally, another 12 hours
or overnight before you make your final observation. So, to complete the lab on time, the beans need
to start the soaking process 48 hours before the due date!
Read the introduction and then follow the procedure given for this lab experiment. Then submit all of
the following to the dropbox.
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Picture requirement (don’t forget the date!): Experiment 1: Submit a picture of all 5
respirometers after initially set up AND the final results. Experiment 2. Submit picture of your
initial set up, a picture of your 3 hour results, and a third picture of your 24 hour results for
experiment 2.
Fill out the data tables and submit them to the dropbox.
Answer the questions below and submit your answers.
Questions to Answer:
After Experiment 1
1. What gas does yeast produce during fermentation? Carbon dioxide gas (CO2)
2. Which substance/s used is/are a monosaccharide? Glucose
3. Which substance/s used is/are a disaccharide? Sucrose, lactose
4. Which substance/s used is/are a polysaccharide? Starch
5. When analyzing your results, it is important to first look at your positive control (glucose)
and your negative control (water). Describe how much gas was produced in each of these
two tubes.
Positive control (glucose): The tube with glucose is the positive control because we already
know that yeast can use it in fermentation, so we know that gas should be produced.
Therefore, a lot of carbon dioxide gas is produced in the glucose tube.
Negative control (water): The tube with water is the negative control because there are no
carbohydrates, so yeast cannot undergo fermentation and no gas should be produced.
Therefore, no carbon dioxide gas is produced in the water tube.
6. Now compare your sucrose, starch, and milk (lactose) tubes to each control and describe
the results for each below:
 Sucrose: The sucrose tube should also have a lot of carbon dioxide gas, because
yeast has sucrase (the enzyme that metabolizes sucrose). There should be a similar
amount of gas in the sucrose tube compared to the glucose tube (positive control).
This is because sucrose is broken down into glucose and fructose, which are
monosaccharides that can then be used in fermentation.
7.
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Starch: The starch tube should have no gas, because yeast cannot metabolize starch.
Starch is a polysaccharide made of many glucose molecules. However, yeast do not
have amylase, the enzyme needed to break down starch into individual glucose
molecules, so no fermentation occurs and no gas is produced.
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Milk (lactose): The lactose tube should also have no gas, because yeast cannot
metabolize lactose. They do not have lactase (the enzyme that metabolizes lactose).
No fermentation occurs and no gas is produced.
Which of these three substances (sucrose, starch, and milk (lactose) were the yeast able to
use for fermentation and which were the yeast was not able to use? Describe why you
came to each conclusion! (3 points!)
Yeast can use sucrose for fermentation. They cannot use starch or milk (lactose). We came
to this conclusion because carbon dioxide gas, a byproduct of fermentation, was only
produced in the sucrose tube. (See question 6 for more detailed explanation.)
8. Using what you know about the substances provided and the information about enzymes
given in the experiment 1 introduction, describe why some substances were better able to
be metabolized by yeast then others.
Sucrose was better able to be metabolized by yeast than starch and lactose because yeast
have sucrase but not amylase or lactase. Without the proper enzymes, yeast cannot
metabolize certain substances.
After Experiment 2
9. What color does bromothymol blue turn in acidic conditions? When neutral? When basic?
Bromothymol blue turns yellow in acidic conditions, green in neutral conditions, and blue in
basic conditions.
10. When carbon dioxide is dissolved in water, which color would bromothymol blue turn if
added?
When carbon dioxide dissolves in water, it forms carbonic acid.
H2O + CO2 => H2CO3
Bromothymol blue will turn yellow.
11. Describe what evidence you have to prove that cellular respiration occurred in at least some
of the beans? Explain.
The evidence proving that cellular respiration occurred is the color change of bromothymol
blue to yellow. Cellular respiration uses oxygen and produces carbon dioxide. If cellular
respiration occurs, carbon dioxide will be produced and will dissolve in water, forming
carbonic acid. Bromothymol blue will turn from green/blue to yellow.
12. Were there differences in the rates of respiration in pre-soaked beans and un-soaked
beans? Describe the differences.
Presoaked beans should have a higher rate of respiration than unsoaked beans. This is
because presoaking the beans causes them to break out of their dormant state and start
growing faster.
13. Propose an explanation as to why this difference in pre-soaked and un-soaked beans may
have occurred.
(See question 12).
14. Were there differences in the rates or respiration in pinto beans vs. kidney beans?
Describe these differences.
Kidney beans should have a higher rate of respiration because they are bigger than pinto
beans.