Sarah Tran
2 November 2009
Period 6
Respiration Lab
Data Collection and Processing:
Raw data turned in separately.
See attached excel for aspect 2 and 3.
[Aspect 3 cont.]
The values for the Germinating Peas and the Dry Peas + beads shown in the
graphs are corrected values after the fluctuating value for the constant (beads, which
should not have had any change in the volume of oxygen) were subtracted from the
original values. Error bars of +/- .02 mL represent any uncertainty within reading the
respirometers that were underwater.
Conclusion and Evaluation:
Aspect 1: Conclusion
As cells undergo cellular respiration, they must intake oxygen. When placed in a
closed environment with a given amount of oxygen, the volume of oxygen decreases as
cells perform cellular respiration. As our data procured, thriving cells, such as
germinating peas, use oxygen, as shown by the decrease in volume of oxygen in the
respirometers. Cells that are dormant or not living, represented by the dry peas + beads,
do not intake oxygen, or at least very little. In fact, the dry peas at 25 degrees Celsius had
a slight increase in volume of oxygen after correction values were accounted for.
Cells also consumed more oxygen at room temperature (25 degrees C) as opposed
to 10 degrees C. Each organism thrives best a given temperature, which is easiest for it to
maintain homeostasis. There was a total of .87 mL oxygen consumed at room
temperature, but only .62 mL of oxygen at 15 degrees C below room temperature. As a
data shows, we can conclude that the germinating peas thrive best and perform cellular
respiration at around 25 degrees C. Again, for the dry, non-germinating peas, there was
little change in the volume of oxygen regardless of temperature.
Aspect 2: Weaknesses and Limitations
The weaknesses and limitations of the lab include splitting the times between two
different class periods, keeping the temperature of the 10 degrees C water constant, and
the accuracy of the respirometers. Splitting the class between two periods was bad
because it gave way to possible error in data collection if there was a lapse in time the
data should be collected, leading to skewed results. Also, any errors of the previous class
would be unknown in the data poll. Keeping the temperature of the water at 10 degrees C
with ice was had to regulate because the temperature that was read by the thermometer
was relative to distance of the ice and the thermometer, not the water as a whole. This
problem can be seen by the fluctuation data of the dry peas in the 10 degrees water bath.
This also means that the change in the volume of oxygen could be a result of something
other than the change in temperature. The accuracy of the respirometers was less of a
problem, but to the point that they leaked oxygen, as shown by changing volume of
oxygen in the control (glass beads). This was less of a problem, as we were able to depict
a corrected value, but the corrected values were based on the assumption that the
respirometers would leak the same amount of oxygen. To the point where that uncertainty
is not accounted for, we cannot tell how much of the oxygen consumption was a result of
respiration. Furthermore, there was only one trial recorded for each set of data tested.
That means that if there was a true problem as the aforementioned, then it would skew
the result and there would be no mediator to show discrepancy in those results.
Apsect 3: Improvements
An improvement for the splitting the experiment between two class period is
having the respirometers already pre-set-up and then have the student just put them in
water and record the data for a shorter amount of time. This way, any errors would be
known by the as the data is collected and there would be no lapse in time between while
recording data. An improvement for keeping the temperature of the ice bath constant
would be to use a container that already regulates cooler temperature, such as a cooler, or
even an electronic water plate maybe. This way, the entire water container could be kept
more accurately at the given temperature. An improvement for the respirometers and the
leaking would be to use a screw cap, which could better hold in the oxygen, as opposed
to a stopper, which could let the oxygen leak more freely. A simple improvement for the
single trial is to share the different data sets between the classes, so that each
experimenter would have not only their own set of data, but also the data of the rest of the
class to use to calculate any great outliers.