Lab 5 Ap Biology Essay

Presentation on theme: "Lab 5: Cellular Respiration 2004-2005. Lab 5: Cellular Respiration Description ◦ using respirometer to measure rate of O 2 production by pea seeds "— Presentation transcript:

1 Lab 5: Cellular Respiration 2004-2005


3 Lab 5: Cellular Respiration Description ◦ using respirometer to measure rate of O 2 production by pea seeds  non-germinating peas  germinating peas  effect of temperature  control for changes in pressure & temperature in room 2004-2005


5 Lab 5: Cellular Respiration Concepts ◦ respiration ◦ experimental design  control vs. experimental  function of KOH  function of vial with only glass beads 2004-2005


7 Lab 5: Cellular Respiration Conclusions ◦ temp =  respiration ◦ germination =  respiration 2004-2005 calculate rate?


9 Lab 5: Cellular Respiration ESSAY 1990 The results below are measurements of cumulative oxygen consumption by germinating and dry seeds. Gas volume measurements were corrected for changes in temperature and pressure. a. Plot the results for the germinating seeds at 22°C and 10°C. b. Calculate the rate of oxygen consumption for the germinating seeds at 22°C, using the time interval between 10 and 20 minutes. c. Account for the differences in oxygen consumption observed between: 1. germinating seeds at 22°C and at 10°C 2. germinating seeds and dry seeds. d. Describe the essential features of an experimental apparatus that could be used to measure oxygen consumption by a small organism. Explain why each of these features is necessary. 2004-2005 Cumulative Oxygen Consumed (mL) Time (minutes)010203040 Germinating seeds 22°C0.08.816.023.732.0 Dry Seeds (non-germinating) 22°C0. Germinating Seeds 10°C0. Dry Seeds (non-germinating) 10°C0.0



Patrick McCrystalCellular Respiration: From O


to CO



This lab provided insight to the process of cellular respiration and how it is affected bytemperature in both germinating and dormant pea seeds. Cellular respiration is an ATP-producingcatabolic process in which the electron receiver is an inorganic molecule. It is the release of energy from organic compounds by chemical oxidation in the mitochondria within each cell.Carbohydrates, proteins, and fats can all be metabolized, but cellular respiration usually involvesglucose: C






+ 6O


→ 6CO


+ 6H


O + 686 Kcal of energy/mole of glucose oxidized.Cellular respiration involves glycolysis, the Krebs cycle, and the electron transport chain.Glycolysis is a catabolic pathway that occurs in the cytosol and partially oxidizes glucose intotwo pyruvate (3-C). The Krebs cycle occurs in the mitochondria and breaks down a pyruvate(Acetyl-CoA) into carbon dioxide. These two cycles both produce a small amount of ATP bysubstrate-level phosphorylation and NADH by transferring electrons from substrate to NAD+.The Krebs cycle also produces FADH


 by transferring electrons to FAD. The electron transportchain is located at the inner membrane of the mitochondria and accepts energized electrons fromenzymes that are collected during glycolysis and the Krebs cycle, and couples this exergonicslide of electrons to ATP synthesis or oxidative phosphorylation. This process produces most of the ATP. Cellular respiration can be measured in two ways: the consumption of O


(how manymoles of O


are consumed in cellular respiration) and production of CO


(how many moles of CO


are produced in cellular respiration). PV = nRT is the formula for the inert gas law, where Pis the pressure of the gas, V is the volume of the gas, n is the number of molecules of gas, R isthe gas constant, and T is the temperature of the gas in degrees K. This law shows severalimportant things about gases. If temperature and pressure are kept constant then the volume of the gas is directly proportional to the number of molecules of the gas. If the temperature andvolume remain constant, then the pressure of the gas changes in direct proportion to the number of molecules of gas. If the number of gas molecules and the temperature remain constant, thenthe pressure is inversely proportional to the volume. If the temperature changes and the number of gas molecules is kept constant, then either pressure or volume or both will change in direct proportion to the temperature.


During the lab, we prepared both a room temperature and a 10


C water bath. Then, wefilled a 50 mL graduated cylinder halfway with water. We added 25 germinating peas anddetermined the amount of water that was displaced. Then we removed the peas, placed them on a paper towel, refilled the graduated cylinder, and added glass beads to the graduated cylinder untilthe volume was equivalent to that of the expanded germinating peas. We removed the beads,refilled the graduated cylinder, added 25 non-germinating peas, and then added more glass beadsuntil the volume was once again equal to the germinating peas’ volume. After all that was done,we prepared another set of peas and beads for the last 3 respirometers. Assembly of therespirometers was the next step. We obtained 6 vials, stoppers, and graduated pipettes. Then we placed a wad of absorbent cotton in the bottom of each vial and, using a pipette, saturated thecotton with about 2-3 mL of 15 % KOH. We then placed a layer of non-absorbent cotton on topof the KOH-soaked cotton in order to protect the peas from the KOH. We placed the first set of germinating peas, dry peas and beads, and beads alone in vials 1, 2, and 3, and the second set invials 4, 5, and 6, then placed the stoppers in each vial. We made slings out of masking tape in


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