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Copy of Lab 6: Cellular Respiration
Transcript of Copy of Lab 6: Cellular Respiration
Chaminade Julienne Catholic High School
Investigation 6 allows the student to observe the rate of cellular
respiration in organisms, seeds in this case, by the consumption of oxygen. Respirometers containing germinating seeds, non-germinating seeds, or glass beads served as a closed environment underwater. When oxygen was absorbed by the seeds, it was visible through the entering of water into the respirometer to displace the lost volume. The water movement was observed in each of the tubes to see which would have the fastest rate of cellular respiration. The results showed that germinating seeds absorbed the most oxygen, indicating those seeds performed the most cellular respiration. INTRODUCTION/Background Information
2-3 paragraphs explaining the science behind the experiment. WHY ARE YOU DOING THIS LAB?
Energy is an essential part of the life and
growth of organisms. Organisms obtain energy through the intake of molecules in their environment. Cellular respiration is a process that allows organisms to break down an organic molecule and produce energy in the form of ATP. It is performed in the mitochondria of cells. In this process, glucose is oxidized and oxygen gas is reduced (The College Board). Glucose is broken down into two pyruvates during Glycolysis which then produces electrons in the Citric Acid Cycle. The electrons are shuttled down an electron transport chain in oxidative phosphorylation and ATP is generated through chemiosmosis.
This lab actively displays the process of cellular respiration in peas. Germinating peas are in a period of great growth and development. They must obtain more energy in order to live. Non-germinating seeds are not growing but still needs energy to survive. Both peas perform cellular respiration. The glass beads serve as a control because it is not an organism and therefore, will not perform cellular respiration. It allows for comparison and analysis of data in the independent variables. The rate of cellular respiration is indicated by the consumption of oxygen gas. When the peas absorb oxygen, water will enter the respirometer to replace the volume lost by the gas. KOH forms a precipitate with carbon dioxide which makes sure that it does not interfere with the lab. Through this lab, the rate of cellular respiration in germinating and non-germinating seeds is able to be compared. The effects of temperature are also able to be observed.
Hypothesis 1 : If germinating and non-germinating seeds are placed in a respirometer to observe oxygen consumption, the germinating seeds will absorb the most oxygen.
Hypothesis 2 : If germinating and non-germinating seeds are placed in a respirometer with varying temperatures to observe oxygen consumption, the seeds in the warmer temperature will absorb the greater amount of oxygen.
Hypothesis 3 : If oxygen consumption of Wisconsin Fast Plant seeds are compared to oxygen consumption of black eyed peas, the black eyed peas will absorb a greater amount of oxygen.
1.Germinating/ non-germinating Wisconsin Fast Plant seeds
2.Thin stem plastic dropping pipettes
8.15% solution of KOH
11.Non- absorbent cotton
1.Prepare a water bath with water at room temperature. 2.Place a cotton ball soaked with KOH into the bottom of the 3 respirometers.
3.Place non-absorbent cotton on top of the cotton balls.
4.Fill a graduated cylinder with 25mL of water
.5.Add 25 germinating peas to the water and record the water displacement
.6.Add the germinating seeds to a respirometer
.7.Fill another graduated cylinder with 25mL of water.
8.Add 25 non-germinating peas to the water
.9.Add glass beads to obtain the same volume displaced as the germinating seeds.
10.Add the combination of glass beads and non-germinating seeds to a respirometer.
11.Fill another graduated cylinder with 25mL of water. 12.Add the appropriate amount of glass beads needed to obtain the same volume displaced as the germinating seeds. 13.Add the glass beads to a respirometer.
14.Place tape across the water bath to allow for a sling. 15.Calibrate the respirometers for five minutes by placing them into the water bath with the open end of the syringe resting on the sling.
16.Inject a small amount of food coloring into the open end of the respirometers.
17.Submerge the respirometers in the water bath and begin to observe.
18.Every five minutes for 25 minutes, observe the changes in mL of water filling the syringe.
19.Compare the results.
References and Acknowledgments
The College Board. (2012). Investigation 6 cellular
respiration. AP biology investigative labs:
An inquiry-based approach. Discussion
Glass beads are non-living and therefore, would not perform cellular respiration. This is why the glass beads were used as a control and resulted in very little or no change of water movement because there was no organism to absorb the oxygen. Germinating seeds had the greatest change in position of water which indicated the greatest consumption of oxygen. This also means that these seeds had the highest rate of cellular respiration. This can be explained because germinating seeds are in their prime time of growth and development. They are in the stage in which the most energy is required to allow the seed to cultivate and stay alive. Once they get past this stage, they are considered non-germinating seeds. Although non-germinating seeds are no longer in a period of extreme growth and development, they still require energy to stay alive. This is why very little observable change in the movement of water was recorded for the non-germinating seeds in 25 minutes.
Varying temperatures of the water bath were tested to observe the rate of cellular respiration in different environments. The respirometers in the cold water bath produced the most change in water position which indicates the greatest oxygen consumption. This means that the peas prefer an environment that is cooler rather than warmer. In a cooler temperature, peas must work harder to maintain homeostasis. They need more energy and must increase the rate of cellular respiration in order to keep a balanced temperature for survival. The room and warm temperatures were easier environments for the peas to live and therefore, required less cellular respiration.
Errors may play a role in the calculation of the movement of water. To improve the data, more precise measurements could have been taken. Accidental changes in pressure or temperature could also affect the outcome of the experiment. The room setting could have been a more controlled environment. Not enough KOH would also impose a problem because the carbon dioxide would not react to form a precipitate (The College Board). It would then sit around in the tube, not allowing for the change in volume. If there is no change in volume, the water will not move in and no changes will be observed. The experiment could be expanded by testing different types of seeds to see which seeds perform the faster rate of cellular respiration. It could also be tested whether different seeds perform better in different temperatures.
The germinating seeds absorbed the most oxygen, indicating the most productivity of cellular respiration, which supports the hypothesis that germinating seeds will perform more cellular respiration than non-germinating seeds. The seeds in the colder environment absorbed the most oxygen. This disproves the hypothesis that seeds in a warmer temperature will perform the most cellular respiration. . QUESTIONS TO ANSWER
1. Using the general gas law (state this law!) and your experience in this lab, give the variables that had to be controlled for your data to be valid. State the controls used for each variable and any means used to correct for the influence of a variable(s).
The general gas law is PV=nRT. P stands for pressure of the gas. V stands for volume of the gas. n represents the number of moles of gas. R is a constant. and T represents the temperature of the gas.
2. From your graph, calculate the rate of oxygen consumption for each treatment:
a. Germ at room temp: .008mL/min
b. Germ at colder temp: .032mL/min
c. Germ at warmer temp: -.0016mL/min
d. Non Germ at room temp: -.0008mL/min
e. Nongerm at colder temp: .004mL/min
f. Nongerm at warmer temp: -.0004mL/min
3. If you used the same experimental design to compare the rates of respiration of a 25 g reptile anda 25 g mammal at 10 degrees C, what results would you expect? Explain your reasoning.
The mammal would respire more because it maintains its own internal body head. In order to do this, the mammal needs to work harder to maintain homeostasis. The reptile is exothermic and easily adapts to its environment.
4. If respiration in a small mammal were studied at both room temperature (21C) and 10C, what results would you predict? Explain your reasoning.
The mammal would respire more at 10C than at 21C because the temperature is less pleasing to the animal and it needs more energy to maintain homeostasis. Therefore, it will more often perform cellular respiration.