11 February 2014
Observing and Analyzing the Rate of Cellular Respiration in Germinating and Non-germinating Black-eyed Peas
If the cellular respiration rate of germinating black-eyed peas and non-germinating black-eyed peas is compared then the germinating black-eyed peas will have the higher respiration rate. II. Background
Organisms need some sort of energy to facilitate their growth and development. Usually, this energy is in the form of adenosine triphosphate, or ATP. Cellular respiration is the process that synthesizes ATP through the three main steps of glycolysis, the citric acid cycle, and oxidative phosphorylation. Essentially, the sugar glucose is obtained by an organism and put through several stages within the three main steps previously mentioned. In oxidative phosphorylation, electrons are passed from a set of proteins called the electron transport chain to one highly unstable atom of oxygen. As the oxygen stabilizes, energy is synthesized and used in combination with energy created by electron movement on the transport chain to push H+ ions against their gradient into the mitochondrial matrix. Once in the matrix, H+ ions diffuse back down their gradient through a protein called the ATP synthase into the inner mitochondrial space. As H+ ions go through the ATP synthase, it rotates, and 34-38 ATP are finally synthesized and ready to be used in other parts of the cell. The overall process of cellular respiration can be written as the equation C6H12O6 + 6O2 -> 6CO2 + ATP (energy) (Campbell & Reece, 2005). One factor influencing rate of cellular respiration is the type of plant or even the stage of life in the single plant. In this experiment, the respiration rates of germinating (growing) versus non-germinating (dormant) peas was compared and analyzed. Usually in cellular respiration, CO2 molecules are released as quickly as O2 molecules are consumed, so no changes in volume occur. In this experiment, O2 is absorbed by the peas as usual, but the CO2 that would normally replace the O2 in overall gas volume is absorbed by KOH, which drives overall gas volume down as respiration goes on (because O2 is continually absorbed). Since germinating peas are growing more than the non-germinating, dormant peas, the germinating peas should absorb more O2 from their environment.
III. Methods and Materials
Non-germinating black-eyed peas (10)
Water 153 mL (51 mL per respirometer)
Germinating black-eyed peas (10, must be in tact)
Room temperature water bath (19°C)
Respirometers (3, must assemble)
Glass Beads (13)
Dry non-absorbent cotton
Assembling the Respirometer- Initial Volume of Water – 51 mL 1. In each of 3 vials, place absorbent cotton on the bottom and soak with KOH solution. 2. Cover with dry non-absorbent cotton
3. To vial #1, add 10 germinating, black-eyed peas
4. To vial #2, add 10 non-germinating, black-eyed peas and enough glass beads to make the volume equal to vial #1. 5. To vial #3, add an equal volume of glass beads, the non-metabolizing control. 6. Cap each vial with a stopper fitted with a pipette, tip pointing outward. Measuring the Rate of Respiration
1. Place three respirometers in a water bath at 19°C (determined using thermometer) with the tips of the pipettes resting on a sling (masking tape) above water level. Allow several minutes for them to equilibrate. 2. Lower the tips of the pipette into the water.
3. Take an initial reading from each respirometer.
4. Take readings from each respirometer at 5 minute intervals for the next 20 minutes. Record data in table. Note:
Gas volume is related to the temperature of the gas. According to the gas law (V=nRT/P), a change in temperature will cause a direct change in volume (Campbell & Reece, 2005). Because the temperature in the respirometers may vary during the course of the experiment, one must correct...
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