Lecture on Cellular Respiration and Fermentation

Introduction

• Personal anecdote about swimming and childhood dreams of having gills.
• Misconception about fish and oxygen.
• Importance of oxygen for organisms including fish, plants, and humans.

Oxygen in Cellular Respiration

• Cellular respiration requires oxygen to produce ATP.
• ATP (adenosine triphosphate): key energy carrier in cells, crucial for powering cellular processes.
• Process involves converting ADP back to ATP through the addition of a phosphate group.

Aerobic vs Anaerobic Processes

• Aerobic Cellular Respiration: Complex process requiring oxygen.
• Anaerobic Respiration: Occurs without oxygen, utilizing alternative final electron acceptors.
  • Some bacteria and archaea can use substances like sulfate.
  • Anaerobic processes allow continuation of glycolysis and the Krebs cycle.

Fermentation

• Occurs when oxygen is not present.
• Allows glycolysis to continue, producing ATP without oxygen.
• Produces less ATP compared to aerobic respiration.

Glycolysis Overview

• Converts glucose to pyruvate, producing 2 ATP and 2 NADH.
• NAD+ is reduced to NADH during this process, requiring regeneration for glycolysis to continue.
• LEO GER mnemonic: Lose Electrons = Oxidized, Gain Electrons = Reduced.

Types of Fermentation

1. Alcoholic Fermentation
   • Conducted by yeast and some bacteria.
   • Glycolysis produces pyruvate and NADH.
   • Pyruvate is converted to ethanol and CO2, using acetaldehyde as an electron acceptor.
   • Application in bread-making: CO2 helps bread rise, ethanol evaporates during baking.
2. Lactic Acid Fermentation
   • Occurs in muscle cells under oxygen debt.
   • Pyruvate is converted to lactate, regenerating NAD+.
   • Previously blamed for muscle soreness; recent research suggests otherwise.
   • Used in yogurt production, contributing to sour taste.

Conclusion

• Fermentation is vital for ATP production in oxygen-depleted environments.
• Highlights the efficiency of oxygen in producing ATP compared to fermentation.
• Encouragement to stay curious and explore further reading.