AP Lab 4
Determining the rate of Cellular Respiration Using Germinating and Dry Peas Purpose: To determine the rate of cellular respiration using dry and germinating peas. Introduction: In this lab, we are investing cellular respiration, specifically aerobic cellular respiration. Aerobic cellular respiration is the process by which cells consume oxygen during the oxidation of glucose and produce CO2 as a byproduct. During cellular respiration, glucose is split into a 6 carbon sugar, G3P through the use of 2 ATP, and then G3P is oxidized to form a 3 carbon molecule, pyruvate. This process is known as glycolosis. After glycolosis, pyruvate enters the mitochondria and is converted into Acetyl CoA. This is done because pyruvate’s carboxyl group is oxidized and given off as CO2 and the remaining pyruvate is oxidized to form acetate. Coenzyme A is then attached to the acetate through the help of sulfur. Acetyl CoA then enters the Citric Acid Cycle where NADH and FADH2 are produced and enter the ETC where oxygen, the final electron acceptor, oxidizes NADH and FADH2 to form water. This equation: C6H12O6 + 6 O2-------→6 CO2 + H2O shows how glucose is oxidized and the different ways of measuring cellular respiration. For this lab, we will be measuring the amount of oxygen consumed by using a respirometer, where the amount of oxygen consumed will be measured by the amount of water taken into the respirometer. Hypothesis: 1. If I place the 3-day germinating peas in the respirometer, then there will be a high amount of oxygen consumption and a faster rate of oxygen consumption in both temperatures.
2. If I place the dry peas and beads in the respirometer, then there will a low amount of oxygen consumption and low rate of oxygen consumption in both temperatures.
3. If I place the glass beads in the respirometer, then there will be no oxygen consumption. Materials:
10 degree Celsius water (us ice if necessary)
Plastic container to hold water
Weights in a plastic bag
Tape (to label respirometers)
100-mL graduated cylinder
Fill the plastic container with 10 degree Celsius water and measure temperature regularly to maintain it. 2.
For respirometer 1, fill a 100-mL graduated cylinder with 50 mL of water. Drop 25-30 germinating peas in the graduated cylinder and record the displacement (this is your volume of the peas). Remove the peas and place them on a paper towel. 3.
For respirometer 2, fill the 100-mL cylinder again with 50 mL of water. Drop as many dry peas and glass beads needed to obtain an equivalent volume of the germinating peas, and then remove them and place them on a paper towel. 4.
For respirometer 3, fill the 100-mL cylinder again with 50 mL of water. Drop as many glass beads needed to obtain an equivalent volume as the two other sets of peas, and then remove them and put them on a paper towel. 5.
Place a small piece of cotton in the bottom of each empty respirometer and, using a dropper, moisten the cotton ball with KOH. *Note: make sure the cotton ball is moist but not dripping KOH because you do not want the KOH getting into the peas. 6.
Place another small piece of cotton on top of the KOH cotton ball to protect the peas against the KOH. 7.
Place the germinating peas, dry peas and beads, and beads alone in each of the corresponding respirometers and put on the stopper/pipette combo on to each respirometer. 8.
Make a sling of tape across the water container and place each respirometer atop of it to allow the pipettes to calibrate for 7 minutes. Meanwhile, place a drop of food coloring at the tip of each pipette so that the food coloring is sitting at the top of the pipette. 9.
After the calibration period, place all 3 respirometers in entirely in the water so that the whole respirometer is under water....
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