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Cellular Respiration Lab
Transcript of Cellular Respiration Lab
•10 Live animals (crickets, earthworms, meal worms)
•Cotton (absorbent and non-absorbent)
•Tweezers Materials (cont.) Respiration Lab Materials:
•Laminated sheet of white paper
•3 Respirometers: Rubber Stoppers/ Pipette Background In this lab, corrected difference calculations were used to find the average milliliters of oxygen consumed at each interval of time. Specifically, the calculation went as follows: 0.9 – (avg. mL of H20 at each time interval). The number .9 is indicative of the initial reading of water in the tube. By subtracting the average amount of water from the initial amount, one calculates the average amount of oxygen consumed in respiration. When graphed (with time on the x-axis and avg. oxygen consumed on the y-axis), one can use the slope of the graph, in mL/sec, to find the average rate of change in the amount of oxygen consumed over time. In other words, the slope gives the rate of cellular respiration in the given time interval.
The rate of respiration in germinating peas was always higher than the rate of respiration in non-germinating peas. The slope was approximately 0.07 in both the room temperature and cold bath trials. The non-germinating peas had a higher respiration rate in the cold water bath (.04) than in the room temperature bath (.0026). Furthermore, the glass beads had a higher respiration rate (.011) than than the non-germinating peas in the cold water bath. This shows that there was error in the experimentation. The results should indicate that glass beads do not respire and that non-germinating peas have a higher respiration rate than nonliving beads. Germination requires more metabolic demands as the pea is no longer dormant. Therefore, the experiment supports the idea that germinating peas respire at a faster rate than non-germinating peas.
In the student designed experiment, earthworms in a cold water environment were found to respire at a faster rate (.03) than in a warm water environment (.014). This was not expected as enzymatic activity is lower in colder temperatures, which means the organism should have a lower respiration rate. The experiment indicated the opposite results. Higher temperature means higher enzymatic activity, but this was not the case in the earthworms' case.
The t-test indicated a an alpha value of 0.919, which is about half of the alpha value needed to reject the null hypothesis. Thus, we do not have enough evidence to reject the null hypothesis in favor of the alternate hypothesis which states that increased temperature means higher rates of respiration in earthworms.
Some error in the current procedure is not enough of a difference in temperature between the two experiments. Furthermore, 'room temperature' water was actually just tap water, and therefore it was not exactly in line with the experiment. Furthermore, volume was not accounted for in the earthworm experiment, only mass. This probably had an affect on the respiration rates. 2 Sample T-Test for Earthworms H: Increased Temperature will increase rate of respiration in earthworms.
H0: Increased Temperature will not increase rate of respiration in earthworms.
p = 0.5, This means that our alpha-value must be 1.860 in order to reject the null hypothesis in favor of the alternate hypothesis.
There are 8 df. Cellular Respiration Lab : Methods Rate of cellular respiration of germinated peas, dried peas, and glass beads as calculated by consumption of O2 & Rate of cellular respiration of earthworms as calculated by consumption of O2 Lab Conclusion Purpose The equation for cellular respiration is: C6H12O6 + 6O2 --> 6CO2 +6H2O+Energy(ATP). The point of cellular respiration is to convert reactants into the main product, ATP. This molecule is a basic unit of energy used to power cellular processes. Water is given off as a bi-product, and CO2 is put through the Citric Acid Cycle in order to release energy in the form of protons and electrons. The Ideal Gas Law is PV=nRT. Here, P stands for pressure; V is volume; n is the # of moles present; R is the universal gas constant; T is temperature. The variable measured by the respirometer is volume: oxygen consumed. Two variables that could affect respirometer readings are the air pressure, and temperature. The difference between germinating and non-germinating peas is that germinating peas have a higher metabolic rate as they are actively growing and using nutrients. On the other hand, non-germinating peas are relatively dormant and therefore smaller in size; fewer nutrients are used up. Dormancy is an important adaptation because it allows non-germinating peas to drastically reduce consumption of nutrients so that the seed can survive. Otherwise, the pea would be useless – all the nutrients would be used up, and no plant would exist. 1) Hold the cotton ball with tweezers. Carefully use a dropper to soak the cotton ball with KOH solution. Fold a layer of nonabsorbent cotton over the soaked cotton ball. Place the cotton ball into the bottom of the tubes. The KOH reacts with CO2 so that only the O2 levels will be recorded. The nonabsorbent cotton will prevent the KOH from poisoning the organisms that are being studied.
2) When experimenting without live animals, keep volume constant. Measure the volume of 25 germinating peas by using the water displacement method. Use the water displacement method again to measure volume of non-germinating peas. Use glass beads to keep the number of peas constant yet still achieve desired volume. Glass beads are also used in the third respirometer as a control group (they don’t respirate). When experimenting with animals, keep mass constant (2g) as it is not possible to keep volume constant. Place the variable organism into the tube.
3) Seal each of the tubes w/ a rubber stopper attached to the respirometer. Weigh each of the tubes down by adding a metal washer to ensure that the tubes sink in the water.
4) Fill the tub with water to create a water bath. If creating a cold water bath, place enough ice in the water and keep track of temperature. It should be 10 degrees. If using room temperature water, ice need not be placed in the bath.
5) When equilibrating, rest the tubes on scotch tape covering the surface of the water tub for seven minutes. After 7 minutes add some drops of food coloring to the tips of the pipettes before the tubes are completely submerged. Make sure that all tubes are submerged at exactly the same time (also, make sure the tubes are positioned so that the mL readings can be read by the scientists).
6) For every three minutes, mark the reading of the tubes until 12 min have passed (the food coloring would have traveled along with the water in the pipette, indicating the volume of water in the respirometer). Seeds: To study how dormancy vs. germination in peas affects cellular respiration rate in cold and warm environments. Earthworms: To study how changes in temperature affects cellular respiration rate of earthworms.