Cellular Respiration and Fermentation
Overview
- Cellular respiration equation: C6H12O6 (glucose) + O2 (oxygen) → CO2 (carbon dioxide) + H2O (water) + ATP + heat.
- Reactants: glucose and oxygen.
- Products: carbon dioxide, water, ATP, and heat.
Importance of Oxygen
- Oxygen is crucial for aerobic respiration as it serves as the final electron acceptor in the electron transport chain.
- Without oxygen, oxidative phosphorylation cannot occur, drastically reducing ATP production.
Types of Respiration
Aerobic Respiration
- Requires oxygen.
- Produces about 38 ATP per glucose molecule.
- Involves four main steps:
- Glycolysis
- Pyruvate oxidation
- Krebs (Citric Acid) Cycle
- Oxidative phosphorylation
Anaerobic Respiration (Fermentation)
- Occurs without oxygen.
- Produces about 2 ATP per glucose molecule.
- End products depend on organism:
- Animals produce lactic acid.
- Yeast produce ethanol.
ATP Production
- Aerobic: Maximum ATP production (~38 ATP).
- Anaerobic: Limited to glycolysis with net 2 ATP.
Organism Types
Facultative Anaerobes
- Can switch between aerobic and anaerobic respiration based on oxygen availability.
- Examples include animals and yeast.
Obligate Anaerobes
- Can only perform anaerobic respiration.
- Typically single-celled organisms with low energy requirements.
- Often found in oxygen-poor environments.
Practical Implications
- Exercise: During intense exercise, muscles may perform anaerobic respiration due to insufficient oxygen, leading to lactic acid buildup and muscle "burn."
- Alcohol Production: Yeast undergoes anaerobic respiration to produce ethanol, used in brewing beer and other alcoholic beverages.
Energy Considerations
- The total energy in glucose remains constant, whether aerobic or anaerobic pathways are used.
- Aerobic respiration optimizes energy extraction from glucose, whereas anaerobic respiration captures less energy.
These notes summarize the differences between aerobic and anaerobic respiration, highlighting the role of oxygen and the energy yield from each process.