Oxygen and Carbon Dioxide Pasco Probeware (Lisa Hellinger)
Author:
Lisa Hellinger, Immaculate Heart High School
Background:
Cellular Respiration: C6H12O6 + 6O2 →6CO2 + H2O + energy
Many cellular processes require energy. Aerobic cellular respiration supplies energy by breaking down glucose. Cells accomplish this task by breaking down nutrient molecules, like glucose, to generate ATP, which can then be used to run cellular processes that require energy. This is a complex process involving a number of enzyme-mediated reactions; however, we can summarize the process in terms of input and outputs with a simple equation:
We will measure how much oxygen is used and how much carbon dioxide is produced when an organism performs cellular respiration.
We will then compare respiration and photosynthesis by collecting oxygen and carbon dioxide data from a small plant.
Photosynthesis: 6CO2 + H2O → C6H12O6 + 6O2
Probe:
An oxygen probe detects the concentration of oxygen in an air sample, in parts per million (ppm). A carbon dioxide probe detects the concentration of carbon dioxide in an air sample, in parts per million (ppm).
Sample Investigation:
Driving Questions:
How do the concentrations of O2 and CO2 change as cellular respiration proceeds?
How do the concentrations of O2 and CO2 change as cellular respiration AND photosynthesis proceeds?
Independent variables: germinated peas, non-germinated peas, plant
Dependent variables: concentration of O2 and CO2
Constants and controls: same pea species, glass beads for a control, use of the same metabolism chambers
Sample Data & Analysis & Interpretation:
Non-germinating peas, glass beads, germinating peas Snapdragon plant
Glass Beads (Control)
The percentage of oxygen and carbon dioxide present in the metabolism chamber with glass beads is constant and consistent with room air indicating that no respiration or photosynthesis is occurring.
Non-germinating Peas
The percentage of oxygen and carbon dioxide present in the metabolism chamber with non-germinating peas is constant and consistent with room air indicating that no respiration or photosynthesis is occurring.
Germinating Peas
The percentage of oxygen and carbon dioxide present in the metabolism chamber with germinating peas shows that the levels start at regular room levels, but over 24 hours the percentage of oxygen drops while the percentage of carbon dioxide rises indicating that cellular respiration is occurring and photosynthesis is not.
Snapdragon Plant
The percentage of oxygen and carbon dioxide present in the metabolism chamber with a plant shows that the levels start at regular room levels. This experiment was started at 5 pm and at hour 10 the graph shows a similar "X" pattern to the germinating peas. This indicates that cellular respiration is using up the available oxygen and producing carbon dioxide. At hour 15 (8 am) photosynthesis is now happening and the oxygen levels have increased while the carbon dioxide levels have dropped off. Students have a hard time remembering that plants do more than just photosynthesize to make their food. Plants need to metabolize the food they have made just like all other organisms. The data below shows evidence of both processes.
Photos:
Carbon Dioxide Sensor Oxygen Sensor
Resources:
