Cellular Respiration: It's Why We Breathe
AP Lab 6
By: Jake Clor
AP Biology
Ms. Hilker
11/07/2013
Hour 6
Group Members
Patrick McBride
Joey Oberliesen
Michael Francisco
Abstract:
Cellular respiration is one of the most important reactions in living organisms. In
this lab, we examined how different organisms produced different amounts of carbon
dioxide from cellular respiration. We tested the carbon dioxide output of crickets,
isopods, peas, and glass beads as a control. To do this, we put a solution of KOH inside a
microrespirometer and put the experimental units in the microrespirometer. We recorded
the movement of our manometer fluid which told us how much carbon dioxide was given
off. Comparatively, the peas produced the least carbon dioxide, then isopods, then
crickets made the most. Some sources of error could include changes in temperature,
sticky walls in the tubing, or movement of the microrespirometer.
Introduction:
Cellular respiration is the reason why organisms need to breath and take in
oxygen. This process bridges the gap between the food that is consumed or produced and
the energy that is acquired from it. The energy gained, ATP, powers vital cellular
functions (AP Lab 6). The overall reaction for cellular respiration has glucose and oxygen
as the reactants and carbon dioxide, water, and energy as the products (AP Lab 6).
The purpose of this lab was to explore how different organisms are using cellular
respiration. We also wanted to reinforce that oxygen is consumed and carbon dioxide is
produced. Due to the presence of the KOH, the carbon dioxide was consumed and the
pressure dropped. We tested crickets, isopods, and peas alongside a control of glass
beads. We hypothesized that the peas would have the least carbon dioxide production
because there would be little CO2 to use in photosynthesis. Furthermore, we
hypothesized that isopods would produce less carbon dioxide because they have a smaller
size than the crickets.
Methods:
In this lab we wanted to test how the amount of carbon dioxide given off during
cellular respiration varied between different organisms. To do this, we prepared syringes
as microrespirometers that had tubes on the end. We coated the tube with soapy water
and then put a cotton ball with KOH on the bottom of the syringes, we then put another
nonabsorbent cotton ball over the first. Next, for our first trials, we put glass beads in one
syringe and isopods in the other syringe followed by replacing the plunger. We put the
plunger down to just under 5 mL and then placed the tip of the plastic tubing in some
food coloring manometer fluid. We then withdrew the plunger to 5 mL to get some
manometer fluid in the tubing. Lastly, we taped the end of the tube with the manometer
fluid to a centimeter ruler and recorded the movement of the droplet over time as the
KOH reacted with the carbon dioxide. We repeated this process once more with another
syringe of crickets and of peas.
Results:
Table 1: This table displays the movement of the manometer fluid in the tube for our
first day of tests. In one syringe we had glass beads as a control and isopods to
experiment with.
Time (min)
1
2
3
4
5
6
7
8
9
10
11
12
Centimeters Manometer Fluid Has Moved
Glass Beads
Isopods
0.2
0.3
0.3
0.7
1.0
1.3
1.4
2.7
1.9
3.5
2.1
4.2
2.4
5.3
2.9
5.6
3.3
6.2
4.7
6.1
5.3
6.6
6.0
7.0
Table 2: This table displays the movement of the manometer fluid in the tube for our
second day of tests. In one syringe we had crickets and the other we had peas to
experiment with.
Time (min)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Centimeters Manometer Fluid Has Moved
Crickets
Peas
0.5
0.4
1.5
0.8
3.0
1.3
3.7
1.7
4.5
2.1
5.0
2.2
5.5
2.6
5.8
2.9
6.3
3.2
6.8
3.5
7.2
3.8
7.5
4.1
8.0
4.3
8.0
4.5
Discussion:
Our hypothesis was that the crickets would require more oxygen than the isopods
and would therefore produce more carbon dioxide, and that the peas would not have
much cellular respiration occurring because there wouldn't be carbon dioxide for
photosynthesis to happen. Our hypothesis was supported for both parts. The crickets did
have a greater change in manometer fluid movement as seen in Table 1 and Table 2
comparatively. This could be due to metabolism, or even the size difference of the
organisms. Also, the change in pressure for the peas was not extremely significant for the
peas as seen in Table 2, but it still occurred. This could have been due to the fact that in
order for cellular respiration to occur, there needs to be glucose present which would
come from photosynthesis. Since there was no carbon dioxide this process couldn't occur,
but since it was a seed, it did have some of its own stored energy to use in cellular
respiration.
The implications of this lab are very important, cellular respiration happens in
parallel with many other processes. This lab showed that environmental factors can
influence the intercellular chemical reactions. This is important for organisms such as
plants that begin underground and can’t have photosynthesis occur to produce glucose.
They need glucose stored in order to carry out cellular respiration. Also, the structure of
the cells was revealed to be important for the exchange of gases over the cell membranes
from inside and outside. All of the three organisms displayed that they used diffusion.
Further tests could include varying the amount of light, type of animals, temperature, or
even type of plant. For example, a leaf instead of a seed might not have any cellular
respiration take place at all, and environmental factors such as lower temperature and
light could also cause organisms to have lower rates of cellular respiration.
Several factors could have contributed error to this lab. One error that was clearly
present was the apparent change in temperature that could influence the pressure in the
microrespirometer. This is known because even the glass beads, which do not undergo
cellular respiration, had a decreasing pressure inside the syringe. Furthermore, not
coating the walls of the tube entirely with soap could have caused the manometer fluid to
stick in place giving us higher values than we should have. Lastly, trivial mistakes such
as bumping into the syringe or misinterpreting the readings -- human error-- could have
also occurred.
Literature Cited
AP Lab Investigation 6. Cellular Respiration. 2013.