Lecture Notes on Cellular Respiration and Fermentation

Introduction

• Personal Anecdote: The speaker loved swimming and wanted to have gills like a fish as a child.
• Misconception about Fish: Believed fish didn't need oxygen; learned they extract oxygen from water using gills.

Importance of Oxygen

• Essential for Organisms: Fish, plants, and humans need oxygen.
• Photosynthesis Misconception: Plants perform cellular respiration and need oxygen, though they produce it.

Cellular Respiration

• Process Overview: Cells use oxygen for cellular respiration to produce ATP.
• ATP: Adenosine triphosphate, a molecule with three phosphates, powers cellular processes.
  • Conversion to ADP: When it loses a phosphate, it becomes adenosine diphosphate (ADP).
• Aerobic Respiration: Requires oxygen; involves complex processes like glycolysis, Krebs cycle, and electron transport chain.
• Video Mentioned: In-depth breakdown available, not covered in this lecture.

Absence of Oxygen

• Organisms Adapting: Some bacteria, archaea, yeast, and muscle cells can function without oxygen.
• Anaerobic Respiration: Some organisms use different electron acceptors (e.g., sulfate) instead of oxygen.
• Fermentation: Focus of this lecture; allows ATP production without oxygen.

Glycolysis Recap

• Process Description: Conversion of glucose into pyruvate, requiring initial ATP but yielding a net gain of 2 ATP and 2 NADH.
• NADH and NAD+:
  • NAD+ Reduction: Gains electrons to become NADH.
  • LEO GER Mnemonic: Lose Electrons = Oxidized, Gain Electrons = Reduced.

Fermentation Process

• NAD+ Regeneration: Critical for glycolysis continuity in fermentation.
• Fermentation Types:
  • Alcoholic Fermentation:
    • By Yeast: Converts pyruvate to ethanol and CO2, regenerating NAD+ through acetaldehyde as electron acceptor.
    • Application: Bread making - CO2 helps bread rise, alcohol evaporates during baking.
  • Lactic Acid Fermentation:
    • By Muscle Cells: Occurs in oxygen debt, converting pyruvate to lactate, regenerating NAD+.
    • Muscle Soreness: Lactic acid once thought to cause soreness, recent research suggests otherwise.
    • Bacteria Use: In yogurt production, contributing to sour taste.

Conclusion

• Appreciation of Oxygen: Fermentation is remarkable but less efficient than aerobic respiration in ATP production.
• Amoeba Sisters Reminder: Stay curious!