Yeast Cellular Respiration Lab
Name:________________________________________________________ Date:_______
The research question is: Which sweetener, glucose or splenda, will
yeast use to do cell respiration?
Background Reading:
All cells need to make energy in order to do all of their functions, including active
transport and mitosis. To make energy, cells do cell respiration: cells take in oxygen
and glucose and make water, carbon dioxide and ATP (energy!).
For you to do cell respiration, you breathe in oxygen and you eat glucose. Then you
breathe out the waste- carbon dioxide- because it is a poison so you have to get it out of
your body. Then you use the ATP to do everything you need to do. Plants and animals
do cell respiration in the mitochondria. Remember, the mitochondria make energy!
Today, we are going to work with yeast
which we use to make bread, cakes,
and beer. Yeast is a eukaryotic cell so it
has mitochondria and it does cell
respiration. Yeast is, specifically, a
fungi. We are going to give some yeast
glucose and some yeast splenda (fake
sugar). Then we are going to see which
sugar lets yeast do the most cellular
respiration.
How are we going to be able to tell if they do cell respiration? Well, we are going to put
a balloon over the test tube that the yeast are in. If the balloon gets bigger, that means
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they are doing cell respiration. Can you figure out why that
means they are doing cell respiration?
Prelab Questions:
1. What is yeast (animal, plant or fungi)?
2. Is yeast alive? How do you know?
3. How do cells make energy?
4. Write the equation for cellular respiration:
5. What is the gas product of cellular respiration?
6. How do you blow up a balloon? Do you think we could blow up a balloon from the gas
released from cellular respiration?
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7. What type of macromolecule is sugar? What is the scientific name for sugar?
8. Fake sugar - like splenda or stevia - doesn’t have any glucose, but still tastes sweet. Do
you think we can use them to make energy if they don’t contain glucose? Why or why
not?
Hypothesis:
If I provide yeast with two types of sweetener, the yeast will use_________________ (glucose or
splenda) to do cell respiration and make the biggest balloon by releasing the most ________.
Materials:
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Test tubes
Glucose
Splenda
Yeast
Heater (or just your hands)
Test tube rack or beaker
Spoons
Balloons
Rubber bands
Marker
Procedures:
1. Get two balloons from the front of the room.
2. Measure the circumference of the balloon by wrapping a string around the middle of the balloon.
Then, measure the string with a rule. Record the circumference in your results table for 0 min.
3. Get two test tubes from the front of the room
4. Label one with glucose and one with splenda.
5. Fill each test tube ⅓ of the way with water.
6. Next add about 1 teaspoon of yeast to each test tube
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7. Then add about 1 teaspoon of glucose to the tube marked glucose and 1 teaspoon of splenda to
the tube marked spenda.
8. Mix the contents of each test tube with a pipette. (One pipette for each test tube.)
9. Place the test tubes in cup and then GENTLY put a balloon over the opening of the test tube. Do
this to BOTH test tubes.
10. Hold the test tubes in your hands to keep them warm so cell respiration will happen faster.
11. After about 30 minutes, check on your balloons.
12. Measure the circumference of the balloon by wrapping a string around the middle of the balloon.
Then, measure the string with a rule. Record the circumference in your results table for 30
min.
13. Find the change in circumference for each balloon (circumference of balloon (cm) at 30 min.
minus circumference of balloon (cm) at 0 min.) and record it in your results table.
Results:
Type of Sweetener
Circumference of
Balloon (cm) at 0
min.
Circumference of
Balloon (cm) at 30
min.
Change in
Circumference
(cm)
Glucose
Splenda
Graph: Make a LINE graph to show how much the balloon increased in circumference from 0 minutes
to 30 minutes.
Don’t forget your units and title!
Title:___________________________________________________________________
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TIME
KEY:
= Glucose
= Splenda
Lab Report Draft
Title: _______________________________________________________________________
Introduction:
The topic of the lab was….
The unit we are studying is …
The topic relates to the unit because ...
This topic is important because….
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The research question was….
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Methods: Write exactly what you did in the lab in a past tense paragraph so I could do the
EXACT same thing just by reading this.
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Results Summary: Write out your data in words here. Just the facts! NO CONCLUSIONS!
The circumference of the balloon over yeast with glucose was ____________________________
after 30 minutes. This means the balloon increased __________ over the 30 minutes.
The circumference of the balloon over yeast with splenda was ____________________________
after 30 minutes. This means the balloon increased ___________ over the 30 minutes.
Conclusion: Use the sentence starters below to write your conclusion in a paragraph
1. Our data supported (or did not support) our hypothesis because…. (include data from your graph or
table as evidence!)
2. The process that we observed in the lab was called ________________ which is...
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3. The reactants the yeast used were…..
4. The products the yeast made were…..
5. The balloon inflated because….
6. The reactant that worked the best was ______________ (glucose or splenda) because….
7. Our results were accurate/not accurate because...
Use the following vocabulary words in your explanation - cellular respiration, glucose, ATP, oxygen,
water and carbon dioxide
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