Name: _______________________________________________________ Period: _____________ Date: ____________
Anaerobic respiration investigation
When oxygen is not present, glycolysis is followed by another pathway. This pathway is called
fermentation. Fermentation releases energy from food molecules by producing ATP. Because fermentation does
not require oxygen, it is said to be anaerobic. During fermentation, cells convert NADH back into the
electron carrier NAD+, which is needed for glycolysis.
This action allows glycolysis to continue producing a steady supply of ATP. The two main types of
fermentation are alcoholic fermentation and lactic acid fermentation.
Yeasts and a few other microorganisms carry out alcoholic fermentation. The equation for alcoholic
fermentation after glycolysis is:
Lactic acid fermentation occurs in your muscles during rapid exercise. The equation for lactic acid
fermentation after glycolysis is:
Scientific Experiment to Test for Metabolism
Metabolism is the sum of the chemical reactions that take place within each cell of a living organism and that provide
energy for vital processes and for synthesizing new organic material.
The purpose of this experiment is to test whether yeast can use energy. Yeast can live without oxygen and do
anaerobic respiration. Yeasts use a special type of anaerobic respiration called alcoholic fermentation to obtain energy.
This fermentation process is used to make bread rise, and to produce alcoholic beverages.
During alcoholic fermentation, yeasts break down high-energy molecules like sugar (glucose) to get the energy they
need (ATP) and give off a gas called carbon dioxide as a by-product of this reaction. The bubbles in alcohol and the air
pockets in bread are from this carbon dioxide gas.
You can buy yeast in the grocery store. This yeast consists of little brown grains. The little brown grains of yeast may
not seem to be alive, but if you put them in water with sugar, the yeast will take up the sugar and use the energy stored
in the sugar molecules to make ATP and carry out the processes of life.
Review Questions
1. What type of respiration does not require oxygen?
A. anaerobic
B. aerobic
C. both A and B
D. none of these
2. What is the first step of cellular respiration that does not require oxygen?
A. glycolysis
B. ETC
C. Krebs
D. Calvin
3. Where does energy come from in all cellular respiration?
A. breaking of chemical bonds in sugar B. forming chemical bonds in sugar
C. breaking of chemical bonds in oxygen
Safety
Tell what each safety symbol means:
1._________________________________
2._________________________________
3.__________________________________
Research Question:
Does yeast metabolize sugar and produce a gas? ____________
Predictions:
Do you expect yeast to produce a gas when sugar is available? _______________________________________________
Do you expect yeast to produce a gas when no sugar or other food is available? _________________________________
Does yeast break down sugars in order to obtain energy to do work?
Hypothesis Statement: ______________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
In your experiment, you will grow yeast in a test tube filled with water and sealed with a balloon.
Procedures to measure alcoholic fermentation:
1) Label each test tube, 0%, 1%, 5%, or 10%.
2) Add 10 mL of the appropriate water or sucrose solution to each tube. Make sure water is at 40 degrees Celsius.
3) For each tube, add 0.5 mL or 1/8 tsp of yeast and put a balloon firmly over the top.
4) With your thumb sealing the top, shake each tube until the yeast is dissolved.
5) Measure the depth of bubbles produced and record the circumference of the balloon by measuring them with a
piece of yarn and metric ruler.
Data
Minutes
Sucrose concentration
Test tube 1:
0% (water only)
Test tube 2:
1% sucrose
Test tube 3:
5% sucrose
Test tube 4:
10% sucrose
0
5
10
15
20
25
Analysis
Graph Title: ____________________________________
Post Lab Questions
1. How do living things release energy stored in sugar?
4. Which part of cellular respiration does not require oxygen?
A. photosynthesis
B. cellular respiration
C. bonding
D. endergonic reaction
A. Calvin Cycle
B. Krebs Cycle
C. Glycolysis
D. Electron Transfer Chain
2. What type of cellular respiration does yeast do?
5. What is the equation for cellular respiration?
A. fermentation
B. lactic acid fermentation
C. aerobic respiration
D. Krebs Cycle
A. C6H12O6 + 6CO2 → 6O2 + 6H2O + Energy
B. C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
C. 6H2O + 6CO2 + Energy → 6O2 + C6H12O6
D. 6H2O + 6O2 +Energy → 6CO2 + C6H12O6
3. What is the first step in cellular respiration?
6. What is not changed in an experiment?
A. Calvin Cycle
B. Krebs Cycle
C. Electron Transport Chain
D. Glycolysis
A. control group
B. experimental group
C. independent variable
D. dependent variable
7. Fill in the ovals with the appropriate molecules.