Morgan Fox
Question:
AP Lab 5: Cellular Respiration
How does the rate of oxygen consumed by germinating peas and non-germinating
peas change over time?
Hypothesis:
In germinating peas, the rate of oxygen consumed will decrease over time, and in
non-germinating peas the rate will remain constant.
Objectives:
Investigate the effect of temperature and germination or non-germination on cell
respiration while demonstrating the relationship of gas laws to the function of a
respirometer.
Variables:
Independent- Time on Minutes Dependent- Rate of Oxygen Consumed
Control- temperature of water bath for vials 1-3, temperature of water bath for
vials 4-6, amount of KOH(1mL) used, volume of peas and beads.
Materials:
20 Germinating Peas, 20 Dry Peas, 225 Glass Beads(approximately), 6 mL 15%
Potassium Hydroxide, 2 Waterbaths, 6 Respirometers(glass vials, graduated
pipets, one-hole stoppers, washers), 6 Absorbent Cotton Balls, 6 Nonabsorbent
Cotton Balls, 1 100 mL Graduated Cylinder, 1 Thermometer, 1 Pipet, 1 Glass
Marking pen, 1 Stopwatch, Ice, Masking Tape, Petroleum Jelly, Food Coloring,
Paper Towels
Procedures:
see attached sheet (A), (B), (C), and (D)
Data:
see attached sheet (D)
Analysis:
The attached graph and above data table show the amount of oxygen consumed
over time by germinating peas, dry peas and beads, and beads only at the
temperatures of 20 degrees and 6-7 degrees Celsius. Our graph clearly shows that
the dry peas and beads in the less than 10-degree waterbath (purple line) had a
high level of oxygen consumption. However, we know this data cannot be
accurate as dry peas are dormant and do not respire (they do not require ATP as
they are not doing any work). This error in data was likely caused by the
movement of vials in the waterbath that occurred from the ice that was added
during the experiment, required to keep the temperature at 6-7 degrees Celsius.
This movement allowed more water to move into the graduated pipet, making it
appear that cellular respiration was, in fact, occurring. Our germinating peas in
the 6-7 degree waterbath, despite some fluctuation due to the bumping of the vial,
consumed very little oxygen.
In the 20-degree waterbath, our germinating peas did, in fact, consume oxygen at
a fairly constant rate. Although we could only record the oxygen consumed over a
twenty-five minute period, these peas had a difference of .05 mL of oxygen
consumed. The dry peas and beads in this same waterbath stayed fairly constant
as well, not having any fluctuation in oxygen consumption excepting that at the
15-minute mark, when the vial was slightly bumped. As dry peas and beads
cannot respire, this data set is contains mostly accurate data. These findings show
that, at room temperature, cellular respiration occurs more easily.
Conclusion:
My hypothesis should be rejected, as my initial presumption of the rate of
respiration in germinating peas was incorrect. From this experiment, we can see
from the germinating peas in the 20-degree waterbath that, over time, the rate of
oxygen consumed increases. However, I was correct in thinking that the
respiration rate of non-germinating remains constant, as they cannot respire
because they are dormant, and therefore are not doing work that requires energy.
As for the temperature difference of the waterbaths, we should see that the 20degree bath allowed the germinating peas to respire at a much faster rate than the
6-7 degree bath. The cold temperature makes it more difficult for the peas to
perform cellular respiration. Organisms have a varying ‘optimal’ temperature
range (in mammals typically at body temperature), and as the temperature
increases or decreases drastically from that range, cellular respiration follows suit.
However, we clearly recorded inaccurate data from the 6-7 degree bath, which
may have arisen from a number of errors (not allowing the respirometers to
equilibrate for the full 5 minutes, moving the respirometers after the experiment
had begun, misplacing the washers along the graduated pipette, etc.). Other
students in our class recorded more accurate data that correctly shows how a
colder temperature slows the respiration rate of germinating peas.
Questions:
1. According to your graph, what happens to the rate of oxygen consumed by germinating
peas over time? What does this indicate to you?
According to my graph, the rate of oxygen consumed by germinating peas increases over time.
This indicates that germinating peas do, in fact, respire.
2. List at least three controls in this experiment.
The controls of this experiment included the volume of peas and beads used in each
respirometer, the temperature of each waterbath (20 degrees and 6-7 degrees), and the amount of
KOH (1 mL) added to bind with the CO2.
3. Explain why the water initially moved into the respirometer.
Water initially moved into the respirometer because, when they were submerged in the baths, the
amount of oxygen that previously filled the pipette decreased.
4. What is the role of KOH in this experiment?
The KOH binds with the CO2 and forms a solid at the bottom of the vial, allowing us to
accurately measure the oxygen consumption without the release of carbon dioxide interfering.
5. How did the KOH affect the water movement in the respirometer?
As the KOH binds with the CO2 and removes that factor from our experiment, it allows water to
flow into the respirometer as oxygen is consumed. Without the KOH, the release of CO2 could
cause the water to flow out of the respirometer or not move at all, ruining our experimental
results.
6. Which of the two pea types, germinating or non-germinating, consumes the most
oxygen? Why?
The germinating peas consume more oxygen that the non-germinating peas as they are doing
work that requires ATP, which is produced through cellular reproduction. The non-germinating
peas are dormant, and therefore do not require energy as they are not doing any work.
7. What was the effect of temperature on pea respiration?
The cold waterbath made it much more difficult for the germinating peas to perform cellular
respiration, whereas the room temperature waterbath allowed the germinating peas to respire at a
faster rate.
8. During aerobic respiration, glucose is broken down to form several end products. Which
end products contain the carbon atoms from glucose? The hydrogen atoms from
glucose? The oxygen atoms from glucose? The energy stored in glucose molecules?
In aerobic respiration, the end product of CO2 contains carbon atoms from glucose. The end
product of H2O contains the hydrogen atoms from glucose. The oxygen atoms from glucose are
contained in the end products of both H20 and CO2. The energy stored in glucose molecules can
be found in the end product of ATP (energy).
9. What is fermentation? What are the two types of fermentation? What organisms use
fermentation?
Fermentation is anaerobic cellular respiration, or respiration without oxygen. The two different
types of fermentation are Alcohol and Lactic Acid. Organisms such as yeast and some bacteria
use Alcoholic Fermentation whereas animals used Lactic Acid Fermentation.
10. Draw a Venn diagram showing how respiration and fermentation are similar and how
they differ.
11. What are the three pathways involved in the complete breakdown of glucose to carbon
dioxide and water? What reaction is needed to join two of these pathways? What are
the substrates and products of this reaction and where does it take place?
The breakdown of glucose to carbon dioxide and water occurs through three pathways:
Glycolysis, Electron Transport Chain, and the Citric Acid Cycle. Pyruvate oxidation is needed to
join the electron transport chain and the Citric Acid Cycle. Pyruvate Oxidation requires pyruvate
(which reacted with the CoA) and NAD as substrates, resulting in acetyl CoA, NADH, and
carbon dioxide as products.
12. Write the letter of the pathway that best fit each of the following processes.
1. Carbon dioxide is given off----(b) Krebs Cycle
2. Water is formed-----------------(c) Electron Transport Chain
3. PGAL-----------------------------(a) Glycolysis
4. NADH becomes NAD+--------(c) Electron Transport Chain
5. Oxidative Phosphorylation-----(c) Electron Transport Chain
6. Cytochrome carriers-------------(c) Electron Transport Chain
7. Pyruvate---------------------------(a) Glycolysis
8. FAD becomes FADH2----------(b) Krebs Cycle
13. Calculate the energy yield of glycolysis and cellular respiration per glucose molecule.
Distinguish between substrate-level phosphorylation and oxidative phosphorylation.
Where does the energy for oxidative phosphorylation come from?
For one molecule of glucose in glycolysis, a total of 6 ATP is yielded, 2 from substrate-level
phosphorylation and 4 from oxidative phosphorylation. Total, one glucose molecule yields about
32 ATP, 4 from substrate-level phosphorylation about 28 from oxidative phosphorylation.
14. You have just performed an activity using plant seeds. Prepare a system where you test
respiration in a small animal. In the space provided below draw what that system
would look like.
15. Your teacher has the flu and the only available substitute knows nothing about cellular
respiration. You are given the responsibility to provide the substitute teacher with the
important background information needed to explain this topic to the next class. Write
a short letter below, explaining cellular respiration to the substitute teacher.
Cellular respiration is an animal’s way of breaking down food into usable energy. The equation
C6H12O6 + 6CO2 == 36 ATP + 6CO2 + 6H2O is the same as saying Glucose + Oxygen ==
Carbon Dioxide + Water + Energy (ATP). Oxygen (O2) is consumed as glucose (C6H12O6) is
broken down into carbon dioxide (CO2) and water (H2O). The energy released in the form of
ATP is captured by the cell and used to do work.
16. Name some other biological processes that are affected by temperature.
Photosynthesis, which is the inverse of cell respiration, is also affected by temperature (think of
how few plants you see in the winter-that’s because it’s too cold for them to photosynthesize).
Also, on a slightly different note, enzymatic activity is definitely affected by temperature as the
enzymes can be denatured if the temperature is too high.