Cellular Respiration Lab
Explore how cells release usable energy from glucose. Compare aerobic cellular respiration with yeast fermentation and investigate the effects of oxygen, glucose and temperature.
Glucose
Aerobic cellular respiration
Select the conditions and press Run Experiment.
🎯 Aim
To investigate how glucose, oxygen availability and temperature influence cellular respiration and to compare aerobic respiration with yeast fermentation.
🧰 Virtual Materials
Cell model, mitochondrion, glucose, oxygen, yeast suspension, sugar solution, fermentation flask, balloon, thermometer and observation table.
📘 Theory
Cellular respiration transfers energy from organic molecules such as glucose into ATP, which cells can use for biological processes.
Glucose + Oxygen → Carbon dioxide + Water + Energy
Aerobic respiration produces much more ATP per glucose molecule than fermentation.
⚖️ Aerobic Respiration vs Fermentation
🫁 Aerobic Cellular Respiration
Requires: Oxygen
Glycolysis begins in the cytosol, while major later stages of aerobic respiration in eukaryotic cells occur in mitochondria.
Products: Carbon dioxide, water and ATP.
Energy yield: High relative to fermentation.
🧫 Alcoholic Fermentation in Yeast
Does not require oxygen.
Yeast can regenerate NAD⁺ through alcoholic fermentation, allowing glycolysis to continue when oxygen is unavailable.
Products: Ethanol and carbon dioxide.
ATP: The ATP associated with this anaerobic pathway comes from glycolysis, giving a net yield of 2 ATP per glucose.
📋 Observation Table
| Trial | Mode | Glucose | Oxygen | Temperature | Relative Energy | CO₂ | Observation |
|---|---|---|---|---|---|---|---|
| Run an experiment and press Record. | |||||||
🧫 Yeast Fermentation Experiment
When yeast is supplied with a fermentable sugar under suitable conditions, carbon dioxide can be produced during alcoholic fermentation. In a classroom demonstration, the gas can inflate a balloon fitted over the flask.
📝 Procedure
- Select Aerobic Respiration.
- Set glucose to Medium, oxygen to High and temperature to 30°C.
- Press Run Experiment.
- Observe oxygen use, carbon dioxide production and relative energy output.
- Record the result.
- Change oxygen availability and repeat the experiment.
- Select Fermentation.
- Change glucose and temperature conditions.
- Run the experiment and observe carbon dioxide bubbles and balloon inflation.
- Record the results and compare the two modes.
🧠 Prediction Challenge
🎓 Quick Viva
1. What is cellular respiration?
It is a set of metabolic processes through which cells transfer energy from nutrients into forms such as ATP that can support cellular work.
2. What is the role of oxygen in aerobic respiration?
Oxygen acts as the final electron acceptor in the mitochondrial electron transport chain.
3. Where does glycolysis occur?
Glycolysis occurs in the cytosol.
4. Where do the citric acid cycle and electron transport chain occur in eukaryotic cells?
The citric acid cycle occurs mainly in the mitochondrial matrix, while the electron transport chain is located in the inner mitochondrial membrane.
5. What happens during alcoholic fermentation in yeast?
Pyruvate-derived intermediates are converted to ethanol while carbon dioxide is released and NAD⁺ is regenerated, allowing glycolysis to continue.
6. Why does the balloon inflate in a yeast experiment?
Carbon dioxide gas produced during fermentation accumulates and expands the balloon.
7. How much ATP is obtained directly from glycolysis per glucose?
The net ATP yield of glycolysis is 2 ATP per glucose molecule.
8. Why can temperature affect respiration?
Cellular respiration depends on enzyme-controlled reactions. Temperature influences enzyme activity, while excessively high temperatures can damage proteins and cells.
✅ Result
The simulation demonstrates that aerobic cellular respiration uses oxygen and provides a much greater ATP yield per glucose than fermentation. Yeast fermentation can proceed without oxygen and produces ethanol and carbon dioxide while allowing glycolysis to continue. Glucose availability and temperature can influence the observed respiration or fermentation rate.