Cellular Respiration Inquiry Lab
Cell respiration refers to the process of converting the chemical energy of organic molecules into a form
immediately usable by organisms. Glucose may be oxidized completely if sufficient oxygen is available by
the following equation:
C6H12O6 + 6 O2(g)  6 H2O + 6 CO2(g) + up to 38 ATP
All organisms, including plants and animals, oxidize glucose for energy. Often, this energy is used to convert
ADP and phosphate into ATP. It is known that peas undergo cellular respiration during germination.
In this activity, you will first use a CO2 or O2 Gas Sensor to determine the respiration rate of germinating
peas. After completing the preliminary activity, you will investigate a research question of your choice.
PROCEDURE
1. If your CO2 Gas Sensor has a switch, set it to the Low (0–10,000 ppm) setting. Connect the Gas Sensor to
the data-collection interface. (if you have an O2 sensor, there is no switch)
2. Start the data-collection program. Allow 90 seconds for the sensor to warm up.
3. Prepare the peas for data collection.
a.
b.
c.
d.
Obtain 25 germinating peas and blot them dry with a paper towel.
Determine and record the mass of the peas.
Place the peas in the respiration chamber.
Place the shaft of the Gas Sensor in the opening of the respiration chamber and lay flat, as shown in
the figure below.
4. Pause 60 seconds, and then start data collection. Data will be collected for 600 seconds (10 minutes).
5. After data collection is complete, use the linear regression function to determine the respiration rate.
Record the respiration rate in CO2 ppm/s or O2 %/s. ____________________
Questions to Consider:
1. Using the respiration rate determined in Step 5 (in CO2 ppm/s or O2 %/s) and the mass of your peas
determined in Step 3 (in grams) determine the normalized respiration rate per gram of peas (in CO2
ppm/s/g or O2 %/s/g).
2. Do the results of this investigation verify that germinating peas respire? How do you know?
3. What do you expect would happen to the rate of respiration if you repeated this investigation with nongerminating peas?
4. Why do germinating peas undergo cellular respiration?
5. Do germinating peas undergo photosynthesis? How could active photosynthesis affect the measured rate
of the reaction?
6. What factors could possibly affect the rate of cellular respiration?
Ideas for Inquiry
CO2 or O2 sensor inside
reaction chamber
Temperature probe in water
outside reaction chamber
Biological sample inside
reaction chamber
CO2 or O2 sensor inside
reaction chamber
pH probe to measure pH of aqueous
solution prior to data collection
Temperature probe for
maintaining constant temperature
Biological sample in aqueous
solution inside reaction chamber
Equipment available: CO2 gas probes, O2 gas probes, temperature probes, pH probes, electronic balances,
ring stands, clamps, boiling water, warm water, ice water, white vinegar (a weak acid, pH≈3), ammonia (a
weak base, pH≈11), sucrose, beakers, test tubes, graduated cylinders, other equipment available upon
request
Organisms available: active yeast, inactive yeast, germinated peas, non-germinated peas, live crickets
(let’s keep them that way!)
You will write a full lab report to describe your experimental design and to report and analyze your results.
Cellular Respiration Lab Questions (Answer these at the end of your lab report)
1. Describe the effect of germination vs. non-germination on pea seed respiration.
2. Describe the effect of temperature on pea seed respiration.
3. Imagine that you are given 25 germinating pea seeds that have been placed in boiling water for five
minutes. You place these seeds in a respirometer and collect data as before. Predict the rate of oxygen
consumption for these seeds and state your reasons.
4. Imagine that you are asked to use respirometers to measure the rate of oxygen consumption for a 25-g
reptile and a 25-g mammal at 10°C. Predict how the results would compare.
5. Imagine that you are asked to repeat the reptile/mammal comparison of oxygen consumption, but at a
temperature of 22°C. Predict how these results would differ from the measurements made at 10°C.