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Enxhi Ferraj
Ms. Rossman
AP Biology
26 January 2012
Cellular Respiration Lab Analysis
Introduction:
Cellular respiration is the process of which the cell (involving the mitochondria) produces
ATP and CO2, and in order to do so the mitochondria takes in O2 and glucose. The purpose of
cellular respiration is to convert chemical energy of organic compounds using metabolic
processes into energy such as ATP which is an necessity for many organisms. Using
germinating peas, we can conduct an experiment in which we can calculate the rates of
respiration using an respirometer apparatus submerged in water. By using the apparatus we can
calculate how much oxygen is being consumed by looking at the pipet of the apparatus (which is
submerged underwater because considering how water pushes on the oxygen so as more oxygen
is being consumed, the oxygen moves down the pipet and water moving up) and seeing as how
oxygen moves down the pipet, the volume of the pipet increases as oxygen decreases and oxygen
decreases due to being used for cellular respiration.The faster oxygen is consumed, the faster
than reaction rate of cellular respiration. Our experiment will include three respirometers; the
first one including regular germinating peas, the second including acrylic beads (as our control
so we can compare rates of of respiration as acrylic beads are not alive hence they are not
supposed to perform cellular respiration) and the third will be our inquiry which will include
germinating peas but submerged in warmer water (around 30◦C) while the other respirometers
will be submerged in water at 20◦C. In order for cellular respiration, CO2 is needed, but in the
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respirometer CO2 would escape, to prevent that potassium hydroxide is added to solidify the
CO2 so our results are undisturbed.
Problem:
Our problem to answer was what consequence does having a warmer temperature in the the
environment have on the rates of respiration whether slowing it down or speeding it up in
organisms?
Hypothesis:
If we place 10 germinating peas into a respirometer apparatus that is submerged in a tank
full of warm water (30◦C) and at five minute intervals record the volume of the pipet as oxygen
decreases for 30 minutes total than the rate of respiration of that respirometer will be higher than
rates of respiration of acrylic beads and germinating peas at 20◦C because in warmer
temperatures enzymes work faster and the enzymes will speed up the oxygen consumption which
speeds up the rate of respiration for germinating peas.
Materials:
•
Pen/pencil, 20 germinating peas, acrylic beads, absorbent cotton balls, non-absorbent
rayon, washers, water, graduated cylinder, potassium hydroxide, glass vials, thermometer, stopwatch, paper towels, dropper, rubber stopper, tank/plastic container.
*Respirometer apparatus is made up of vial, washers, pipet, rubber stopper,
Procedure:
1.
Gather all materials
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2.
Fill a 100 mL graduated cylinder with 50 mL of water than add 10 germinating peas than
record the reading of the water now in the graduated cylinder. How much the water moved up
from the 50 mL from adding the 10 germinating peas in is the volume of the peas. Record data.
Remove the peas by removing the water from the graduated cylinder and than setting the peas on
a paper towel to dry.
3.
Place 50 mL of water back into the graduated cylinder but now add acrylic beads until the
water level is the same as that of the germinating peas you recorded earlier.You’ll want the water
level to be as accurate as possible. Record the volume and removed the water and the beads from
the graduated cylinder and set the beads to dry on a paper towel.
4.
Repeat step # two again with 10 more germinating peas, these peas will be used for the
inquiry section of the lab. Be sure to label.
5.
Take three glass vials (be sure to label them; one for the germinating peas, one for acrylic
beads, one for inquiry germinating peas) and place and push an absorbent cotton ball to the
bottom of each of the vials.
6.
Use a pipet to add one mL of 15% potassium hydroxide to the cotton ball of each of the
three vials. (Use with caution)
7.
To each of the vials, add a piece of non-absorbent rayon (to prevent the peas/beads from
being affected by potassium hydroxide) on top of the cotton ball recently soaked in potassium
hydroxide. Do not push down on the rayon.
8.
To vial one, add the 10 germinating peas.
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9.
To vial two, add the amount of acrylic beads that equaled the volume of the 10
germinating peas (from step # three).
10.
To vial three, add the 10 germinating peas (this is your inquiry vial).
11.
Insert the non-tapered end of a pipet into the wide end of the rubber stopper (non-tapered
end pointing away from the stopper and so that the pipet reaches just beyond the bottom of the
rubber stopper. This step should be repeated three times, as one piper and rubber stopper is
needed per vial and you have three vials.
12.
Insert the rubber stopper into the vial ( a tight seal should be created) and place a/some
washers over the pipet so it slides down the pipet and rests on the rubber stopper (these washers
are to prevent the respirometer from floating when submerged). This step should should be
repeated three times as there is three vials.
13.
Place a thermometer and vials 1 and 2 in the tank with 20◦C water so that the pipet tips
rest on the edge of the tank (respirometer is not fully submerged as pipets are sticking out of
water). This step allows the respirometers to equilibrate and should last ten minutes.
14.
Repeat step # 13 with vial 3 (inquiry germinating peas) except place the respirometers in
a different tank with 30◦C water instead of 20◦C.
15.
Turn each of the three respirometers so that the graduation marks on the pipet are visible
and facing up. Removed the pipets off the sides of the tank and completely submerge the
respirometers under the water and do not touch the respirometers for the rest of the experiment
(as heat from contact make affect the results).
16.
Let all three respirometers equilibrate for another five minutes.
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17.
Be sure to read all the of the respirometers to the nearest 0.01 mL and take the
temperature of the water in each of the two tanks to record any temperature instability. Create a
table and record the initial readings of volume (mL) and the temperature of the water in the tank
(◦C) for each of the respirometers.
18.
Record readings of volume and temperature for each of the respirometers every five
minutes for a total of 30 minutes.
19.
Once 30 minutes has passed, calculate the difference and corrected difference for each
result and record data. *Difference= (initial volume reading at time 0) - (volume reading at time
X). *Corrected difference= (initial pea reading at time 0 - pea seed reading at time X) – (initial
acrylic bead reading at time 0 – acrylic bead reading at time X). Graph results.
20.
Clean up work area.
Constants:
•
Same volume of germinating peas and acrylic beads put into respirometers, the pipets
were all the same and set up very similarly, same time intervals for each of the respirometers
(five minutes), same amount of overall time (30 minutes) for each of the respirometers, same
amount of potassium hydroxide (1 mL per respirometer), same size and type of water tank, same
type of germinating peas, same type of acrylic beads (all kept uniform).
Variables:
Independent variable was the temperature of the water tank ( we changed it to 30◦C instead of
20◦C for our inquiry germinating peas).
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Dependent variable: Oxygen consumption of the germinating peas and beads ( we measured this
by how much the volume of the pipet increased over time, as oxygen consumption increased,
pipet volume also increased).
Control:
Our control for this experiment was the acrylic beads respirometer (acrylic beads do not
breathe so we did not expect any cellular respiration as they were not alive, but if the volume of
the pipet did increase which would usually hint at oxygen consumption but beads do not
consume oxygen so we knew that the room temperature and pressure was affecting the volume
of the pipet so we could now create a corrected difference which accounted for the room
temperature and pressure interfering with our data). *Corrected difference= (initial pea reading at
time 0 - pea seed reading at time X) – (initial acrylic bead reading at time 0 – acrylic bead
reading at time X).
Data/Calculations:
*See next pages for table and graph
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Cellular Respiration Lab Data Results
Germinating Peas
Temperature (◦C)
Time (minutes)
Volume Reading
(mL)
Difference
20 ◦C
20 ◦C
20 ◦C
20 ◦C
20 ◦C
20 ◦C
20 ◦C
0
5
10
15
20
25
30
0.25
0.27
0.29
0.31
0.32
0.35
0.37
0
-0.02
-0.04
-0.06
-0.07
-0.1
-0.12
Corrected
Difference
(Bewteen
Germinating
Peas and Acrylic
Beads)
0
0.02
0.01
0
0
-0.03
-0.05
Acrylic Beads
Temperature (◦C)
Time (minutes)
20 ◦C
20 ◦C
20 ◦C
20 ◦C
20 ◦C
20 ◦C
20 ◦C
0
5
10
15
20
25
30
Volume Reading
(mL)
0.19
0.23
0.24
0.25
0.26
0.26
0.26
Difference
0
-0.04
-0.05
-0.06
-0.07
-0.07
-0.07
Germinating Inquiry Peas (in warm water)
Temperature (◦C)
Time (minutes)
Volume Reading
(mL)
Difference
30 ◦C
30 ◦C
28 ◦C
27 ◦C
26 ◦C
26 ◦C
25 ◦C
0
5
10
15
20
25
30
0.1
0.125
0.21
0.34
0.48
0.61
0.75
0
-0.025
-0.11
-0.24
-0.38
-0.51
-0.65
Corrected
Difference
(Bewteen Inquiry
Peas and Acrylic
Beads)
0
0.015
-0.06
-0.18
-0.31
-0.44
-0.58
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Calculations for table above involve these formulas: *Difference= (initial volume reading at time
0) - (volume reading at time X). *Corrected difference= (initial pea reading at time 0 - pea seed
reading at time X) – (inital acrylic bead reading at time 0 – acrylic bead reading at time X).
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Amount of oxygen consumed (in mL)
Cellular Respiration Lab Graph for Amount of
Oxygen Consumed over a span of 30 minutes by
Germinating Peas in a 20◦C waterbath and
Germinating Peas (Inquiry) in a 30◦C waterbath
0.7
0.6
0.5
Germinating Peas in a
20 ◦C waterbath
0.4
0.3
0.2
0.1
0
0
5
10
15
20
25
30
Time (in minutes)
*This graph shows the corrected difference for the oxygen consumption of both the regular and
inquiry germinating peas because the corrected difference takes into account the interference of
the pressure and temperature of the room environment on the volume reading of the pipet. Also,
these corrected difference values are negative in the chart but not in the graph because corrected
difference is directly related to oxygen consumption and oxygen consumption cannot be negative
so the absolute value of the corrected difference is taken to recieve positive oxygen consumption
values.
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Average Rate of Respiration for Germinating Peas in 20 ◦C waterbath
and Inquiry Germinating Peas in 30 ◦C waterbath
Time
Intervals (in
minutes)
0 to 5
5 to 10
10 to 15
15 to 20
20 to 25
25 to 30
Germinating Peas in 20 ◦C
waterbath Rate of
Respiration
Germinating Peas in 30 ◦C
waterbath (inquiry) Rate of
Respiration
0.004
-0.002
-0.002
0
-0.006
0.004
0.003
-0.015
-0.024
-0.026
-0.026
-0.028
Overall
0.002 mL/min
0.02 mL/min
Average rates
of Respiration
*Rate of Respiration = (y2-y1)/(x2-x1) In this case you are using the corrected
differences, for example for time interval bewteen 0 and 5 for the germinating peas in 20 ◦C
waterbath you would take corrected difference of 0.02- corrected difference of 0 / by 5 – 0 so
(0.02-0)/(5-0)= 0.004.
*Average Rate of respiration = Rates of respiration added together divided by amount of
rates of respiration (in this case six).
*The Rates of Respiration are positive because originially you get negative numbers but
you cannot have negative rates of respiration as rate of respiration is oxygen consumption and
you cannot have oxygen consumption.
Conclusion:
In this experiment our problem to answer was what consequence does having a
warmer temperature in the the environment have on the rates of respiration whether slowing it
down or speeding it up in organisms? Our hypothesis was if we place 10 germinating peas into a
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respirometer apparatus that is submerged in a tank full of warm water (30◦C) and at five minute
intervals record the volume of the pipet as oxygen decreases for 30 minutes total than the rate of
respiration of that respirometer will be higher than rates of respiration of acrylic beads and
germinating peas at 20◦C because in warmer temperatures enzymes work faster and the enzymes
will speed up the oxygen consumption which speeds up the rate of respiration for germinating
peas. I accept and support my hypothesis because it turned out to be correct. We were able to
figure out that the average rate of respiration. We were able to figure out the average rate of
respiration because the change in volume of gas in the respirometer was directly related to the
amount of oxygen consumed. So for example, the regular germinating peas volume reading for
zero minutes was 0.25 mL, five minutes 0.27 mL, for 10 minutes 0.29 mL, 15 minutes 0.31 mL,
20 minutes 0.32 mL, 25 minutes 0.35 mL, and for 30 minutes 0.37 mL. So the volume reading
showed us that the volume of the pipet was increasing over time which had to mean oxygen was
leaving the pipet and being consumed by the peas for cellular respiration. But we couldn’t just
base our results off the volume reading because interferences from room air conditioning and
heating and pressure could affect the volume of the pipet therefore affect our results, so we had
to create a corrected difference which accounted for those possible errors. We created the
corrected difference by using the control group of acrylic beads. We knew acrylic beads were not
living, so therefore they could not breathe, and did not perform cellular respiration which means
that they should not consume and oxygen. But our results showed that the volume reading did
increase over time ( a little) for the acrylic beads such as 0 minutes, the volume reading was 0.19
mL, 5 minutes 0.23 mL, 10 minutes 0.24 mL! Beads are not supposed to breathe so how is the
volume increasing when no oxygen is being consumed? This we could blame on the room
interferences so now we knew that our results could vary so to fix this we subtracted the
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difference (difference of volume readings between each time interval) of the germinating peas
from the difference of the acrylic beads and this way we found out actually how much oxygen
was consumed. We were able to repeat this procedure with the germinating inquiry peas since we
could also calculate the difference between time intervals for the germinating inquiry peas and
calculate the corrected difference by subtracting the differences of the germinating inquiry peas
from the differences of the acrylic beads. Since the corrected differences are related to oxygen
consumption, we could assume that by making each corrected difference positive such as the
corrected difference of -0.44 for germinating inquiry peas at 25 minutes to 0.44, we could
assume that 0.44 is also how much oxygen was consumed at 25 minutes for the germinating
inquiry peas. Now that we have oxygen consumption calculated, we could figure out rates of
respiration by a formula. For example, for the germinating inquiry peas, to figure out the rate of
respiration for the time between 0 and 5 minutes, you would take the corrected difference of
0.015 subtract it from 0 than divide by 5 which is subtracted from 0: (0.015-0)/(5-0) which gives
you the rate of respiration for that interval as .004 mL per minute. You can figure out the rest of
the rates of respiration for the rest of the five intervals of germinating inquiry peas the same way.
Now we had to calculate the average rate of respiration so we took all the rates of respiration for
the germinating inquiry peas and added them together and divided by six because there were six
intervals overall and got an average rate of respiration for the germinating inquiry peas to be 0.02
mL per minute. Since 0.02 ml per minute is larger than the regular germinating peas rate of
respiration which was 0.002 ml per minute, this shows that the rate of respiration does increase
in warmer environments such as the inquiry warmer environment because the enzymes do work
fast therefore oxygen being consumed faster which is shown for the inquiry germinating peas (at
0 minutes 0 mL of oxygen consumed, at 5 minutes 0.015 mL, at 10 minutes 0.06 mL vs. the
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regular germinating peas oxygen consumption which was at 0 minutes 0 mL of oxygen
consumed, at 5 minutes 0.02 mL, at 10 minutes only 0.01 mL rather than 0.06 mL which the
inquiry germinating peas had consumed). In conclusion, I support my hypothesis but would need
to repeat the experiment for more accurate results.
Validity:
Some things that could have gone wrong in this experiment are that when we
were timing the intervals for the respirometers, we would have different people watching the
stop-watch and not really being focused on the stop-watch as more accurately as we could have.
This could affect our experiment because if we didn’t time correctly, than we could have gotten
the wrong volume reading at the wrong time, so than we would have gotten the wrong corrected
difference, wrong oxygen consumption and wrong rate of respiration. Oxygen was being
consumed fast so if we were off by 10 seconds it could have made a large impact on our actual
rate of respiration. Also, we could have read the temperatures of the thermometers and volume
readings of the pipets wrong because since we did all three respirometers at once, the intervals
for each would end at the same time and we would scramble to try and read the markings as
quickly and accurately as possible while telling each other and while trying to write the
information down. This could have affected out experiment because we were disorganized, and
what could have looked like a volume reading increasing, could have really been a volume
reading staying the same which would have had a domino effect on our rate of respiration in the
end. Something else that could have gone wrong is the water of our inquiry water tank kept
cooling and cooling as time went on. This could have affected our results because now we don’t
know for sure if the corrected difference for the inquiry is all the correct because even though we
thought we calculated for the temperature and pressure changes in the room, the fact that the
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experiment itself had a decreasing temperature could have highly affected us by giving us the
wrong volume reading in the first place so we would never know if our calculated difference is
actually correct.
Some things that we could fix about our experiment is that instead of having a different
person time the stop-watch each time, we could have each person assigned to a specific job and
have only one person watch the watch which will create less confusion and let us be more
focused on the task at hand instead of fumbling around who is going to watch the watch next so
maybe we could have gotten more precise on the millisecond markings which would have
provide more accuracy in the end for our rate of respiration. Something else that we could have
fixed is starting each respirometer at a different time, so that when one respirometer is ready to
be measured, we can focus in on just that one while the other respirometers have different times
to be checked at. Also, since we have three people in our lab group this would have worked
because each person could have been responsible for their own information and own stopwatches and own respirometer and thermometer which would have provided a lot more ease into
getting the correct markings instead of trying to rush and potentially seeing the wrong volume
reading. Another thing that we could change is the cooling of the water tank for our inquiry lab.
We could have changed this by using some sort of a heater like Bunsen burner nearby to
constantly keep the water at a warm temperature. This would have provided us with the
reassurance that our correct differences are actually correct so that our oxygen consumption is
accurate and our rates of respiration are also accurate because with the temperature staying
constant instead of fluctuating, we only have to take into account the room temperature, not two
sources of temperature variation.
Application:
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This experiment is applicable to the real world because as you look in exotic
jungles or even a florist shop, you notice that the environment is usually warm, but not too hot to
dry out the plants. The reason is because as this experiment shows us, rates of respiration are
faster under warm conditions. So the warmer the environment, the faster a plant will perform
cellular respiration because the enzymes working in the metabolic processes of the mitochondria
of the plant work often in their prime in warmer conditions so when these enzymes are working
in their prime, the faster the reactions. The faster the reactions, the more oxygen is consumed
therefore the higher the rate of respiration but also the more ATP ( and CO2) is produced so the
plant has more energy to thrive and perform necessary daily functions so this is why often
jungles or gardens thrive in warmer environments because the plants produce ATP at their
optimum in warmer environments, and by producing CO2, they can use that CO2 to jumpstart
photosynthesis which also creates glucose (necessary for the plant to live).
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