Biol 1440, Principles of Biology I

Principles of Cellular Processes
Aerobic Respiration


Aerobic respiration is the key metabolic process of producing cellular energy in eukaryotic and some prokaryotic cells.

Chemical Equation:
Glucose (C6H12O6) + 6 O2       6CO2 +6H2O


1.  Examine how biologists study a metabolic pathway using aerobic respiration as a model

2.  Conduct two directed investigations on respiration rates in yeasts.

3.  Learn the uses and limitations of a CO2 sensor.

Research Questions

1. How many ways could you measure aerobic respiration?

2. Do plants undergo aerobic respiration? What cell organelle would a plant need for respiration? Would a fungus have the same or a different organelle?

3. How could you measure the effects of the various pathway components on the rate of aerobic respiration?

  • Which pathway component produces the most CO2/glucose? Glycolysis, Kreb's cycle, electron transport?



Raven, Ch 9 How Cells Harvest Energy

CO2 Sensor Operation

Yeast Biology                         

PreLab Quiz

Self-Test  on  Aerobic Respiration

Students need Graph paper, Marking pen, Calculators
Prepare your lab notebook by completing the two tasks for each Directed Investigation.

Directed Investigation 1.



Directed Investigation 2.




Experimental Set Up

Is Glucose required for aerobic respiration?
1.  Write a hypothesis for this researchable question.

2.  What treatments would you need to test a hypothesis related to this question?  What treatments would be the controls?

Does respiration rate change with glucose concentration?
1.  Write a hypothesis for this researchable question.

2.  Construct a graph that predicts how results supporting your hypothesis would look.

Suggested volume for all runs is 50mL, but students can reduce it to a minimum of 20mL.

1.       Yeast should be suspended in no more than 100mM glucose by diluting your stock solution.  

The final volume should be no more than 50mL.  

Stock yeast solution should have a  biological activity ranging from 45-50mg/mL.  Ask your instructor for the specific biological activity.

2.       Yeast need 3-5 min to begin active respiration.

3.       Add respiring yeast to a clean 125mL flask with a stir bar just before data collection to avoid flask from building up high levels of CO2.

4.       Adjust the speed of the stir plate so that the solution is visibly moving to just forming a slight whirlpool.

5.       A data collection table should be constructed before beginning.

6.       A minimum of 10 CO2 readings or 20 sec. of data collection should be used to calculate aerobic respiration rate, AR-rate (ppm CO2/sec).

7.       Remember to fan the sensor down to ambient CO2 levels below 500ppm before beginning a new run.

Do NOT Breath Directly on the Sensor

Unplug CO2 Sensor after lab