Cellular Respiration Lab

Christi BarrBlock 421 November 2009

Cellular Respiration and Oxygen Consumed in Peas

Aspect 1The purpose of this lab is to measure the oxygen consumption during germination in order to measure the cellular respiration rate in both germinating and non-germinating peas at different temperatures. We are trying to see how temperature affects cellular respiration among both categories of peas. The independent variable is the time of each reading. The dependent variable is the volume of oxygen consumed. The control is the respirometer with glass beads in it.

HypothesisKnowing that all living things undergo cellular respiration, I predict that the germinating peas will consume the greatest amount of oxygen, while the dry peas will consume less and the glass beads will consume none. Also, I predict that higher temperatures will increase the rate of oxygen consumption.

Aspect 2, 3 Materials

100-mL graduated cylinder Dried peas Germinating peas Glass beads Ice 2 tubs of water (one at room

temperature and one at 10 °C) KOH Dropper Absorbent cotton

Nonabsorbent cotton Timer Thermometer Paper towels 6 vials 6 Stoppers 12 washers 6 pipettes Food coloring

Procedure1. Set up two tubs of water, one at room temperature and the other at 10 °C (add ice

as needed).2. Fill a 100-mL granulated cylinder with 50 mL of water and place 25 germinating

peas in it to determine the amount of water displaced and then place the peas aside.

3. Refill the cylinder and add 25 dry peas in, and then continue to add glass beads until the volume is equal to that of the germinating peas.

4. Once again, refill the cylinder and add only glass beads until the same volume is reached.

5. Repeat steps 2-4 again to obtain the vials for the other tub of water.6. To assemble the respirometer, put a small piece of absorbent cotton in the bottom

of each vial and soak it with KOH.7. Then place a wad of dry nonabsorbent cotton on top of that.8. Place the first set of germinating peas, dry peas and beads, and beads in each vial.

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9. Insert the stoppers and place two washers around the pipettes.10. Repeat steps 8 and 9 with the second set of peas.11. Create a sling connecting each side of the water tubs to rest the pipettes on.12. Place the vials in the water with the pipettes on the sling for 7 minutes to allow

for equilibration.13. After 7 minutes, place a drop of food coloring at the end of each pipette and lower

all into the water at the same time.14. Wait three more minutes and then collect the first set of data as the initial position

of water15. Every 5 minutes for 10 minutes take readings of the water position in each

pipette.

Aspect 4

Measurement of O2 Consumption by Soaked and Dry Pea SeedsTemp (°C)

Time (min)

Beads Alone Germinating Peas Dry Peas and BeadsReading at time x

(mL)

Difference(mL)

Reading at time x(mL)

Difference(mL)

Corrected difference

(mL)

Reading at time x(mL)

Difference(mL)

Corrected Difference

(mL)

20 0 .05 .05 .065 .06 .01 .1 .05 .04 .06 0 .0910 .06 .01 .15 .1 .09 .06 0 .0915 .06 .01 .18 .13 .12 .06 0 .0920 .06 .01 .21 .16 .15 .06 0 .09

11 0 .12 .14 .1

5 .1 .02 .18 .04 .02 .1 0 .08

10 .07 .05 .20 .06 .01 .07 .03 .02

15 .05 .07 .22 .08 .01 .05 .05 .02

20 .06 .06 .24 .1 .04 .04 .06 0Uncertainty: +/- .01 mL

+/- 1°C

Difference: (initial reading at time 0) – (reading at time X)Corrected Difference: (initial pea seed reading at time 0 – pea seed reading at time X) – (initial bead reading at time 0 – bead reading at time X)

Aspect 5

Rate of Oxygen Consumed per MinuteCondition Calculation Rate (mL O2/minute)

Germinating Peas/ 11°C |(.12-.14)| / 20 .001Germinating Peas/ 20°C |(.06-.05)| / 20 .0005Dry Peas/ 11°C |(.12-.1)| / 20 .001

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Christi BarrBlock 421 November 2009Dry Peas/ 20°C |(.05-.06)| / 20 .0005

Aspect 6

This graph shows the amount of oxygen consumed in each vial. From the graph, it is clear to see that the germinating peas produced much more oxygen than that of the dry peas. Also, the peas at the colder temperature seem to have worked better.

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This graph shows the rate of oxygen consumed in each condition. From the graph, one can see that the germinating peas and the dry peas both had the same rate at each respective temperature.

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Christi BarrBlock 421 November 2009This graph shows the corrected differences of each pea and the oxygen consumed. Here, it is easy to see that the germinating peas at the higher temperature consumed more oxygen than the others.

Aspect 7The data from this lab supported my hypothesis in that the germinating peas consumed the most oxygen and that the peas at the warmer temperature underwent cellular respiration at a faster rate. This lab showed that the rates of cellular respiration depend on whether or not a seed is germinating and the temperature in which it occurs. Cellular respiration works better in warmer temperatures than it does in colder temperatures.The germinating peas consumed the most oxygen because they need more oxygen as they are the most active. The dry peas did not consume oxygen because they were not active, however the readings how a change which can be accounted for because of atmospheric pressure. Also, the glass beads did not consume any oxygen because they are nonliving and again, any changes can be accounted for because of atmospheric pressure, which is why they were used, so they could act as a control for the experiment. The purpose of the KOH in this lab was to remove the carbon dioxide that was made during cellular respiration and make potassium carbonate. This was needed so the carbon dioxide was removed so the volume change of gas in the respirometer was proportional to the amount of oxygen that was consumed. During cellular respiration oxygen was consumed so the volume in of gas in the tube decreased which caused a decrease in pressure in the tube as well.

Aspect 8During this experiment, the temperature of the water tubs could easily have changed. In fact, the tub that was filled with 11°C water ended up being 14°C. This happened because we ran out of ice so we were unable to keep the temperature down. The stoppers of each vial could have been loose which would cause errors to occur. Reading the pipettes was difficult and they were not all read at exactly the five minute mark which would definitely have skewed our results. Also, the tubs may have been touched slightly or moved which would have disturbed the vials and cause false results. There could also be mathematical errors in the calculations of differences and corrected differences and the rate of oxygen consumption. While measuring the volumes of the peas, errors could have been made which would have given the vials different volumes, again skewing the results.

Aspect 9In order to improve this lab, I would spilt the work up between two lab groups, allowing more time to be spent on each vial which would in turn decrease the amount of errors made while setting up the experiment. Also, creating a better environment so that the tubs of water could not be as easily disturbed would be better. Perhaps a smaller table so the pipettes could be read without possibly bumping into the table and causing disturbances to the vials.

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Christi BarrBlock 421 November 2009Application Questions1. In addition to dry hay, dairy farmers also store corn silage to feed the cows in the winter. Corn silage is green corn stalks that are chopped up and stored fresh and wet in the 50 foot silos next to the barn. This green plant material provides a lot of supplemental nutrients for the cows beyond the dry hay. Often the stored silage oozes liquid that collects at the base of the silo. The feral cats that populate every dairy farm (to control mice in the barns) often make the mistake of drinking this liquid, leaving them sick and woozy. Explain what the liquid is and why it makes the cats sick.

The liquid at the base of the silo is called silage effluent and is a fermented liquid that comes from the corn. When the liquid first appears, it combines with yeast found in the air and other natural bacteria and becomes fermented. The yeast changes the sugars in the liquid into carbon dioxide and ethanol. When the cats drink this, they are basically getting drunk, causing them to get sick. Also, the liquid has bacterial fermentation products and also contains some nitric acid that also causes the cats to get sick when they ingest it.

2. Explain how each of the following work and what they all have in common - oligomycin, cyanide, 2,4-Dinitrophenol (DNP)

Oligomycin causes the cell to be unable to produce its own energy because it blocks the protein channel that is needed to phosphorilate ADP. In large amounts, cyanide causes cells to not be able to use oxygen. 2, 4-Dinitrophenol (DNP) causes lots of energy to be used but doesn’t produce any ATP so the cell cannot do any work. All of these substances affect the way a cell uses and produces ATP and poison the cell so it cannot function properly. The first two change the cell so it simply cannot create any more energy while DNP causes the cell to use all the energy in the cell so it is unable to create any more ATP. All of these substances will cause the cell to die because it causes the cell to run out of energy and without energy, cells cannot stay alive.

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Cellular Respiration Lab