Glycolysis and Fermentation

Glycolysis and Pyruvate Metabolism

• Glycolysis produces 2 ATP, 2 NADH, and 2 Pyruvates.
• Pyruvate can be further metabolized through either fermentation or respiration.

Fermentation

• Occurs in the cytosol and has a low energy yield.
• Two types of fermentation:
  • Lactic Acid Fermentation: Occurs during intense muscle activity, reoxidizes NADH to sustain glycolysis, and involves the key enzyme lactate dehydrogenase.
  • Ethanolic Fermentation: Occurs during fermentation of beer and bread by yeast, releases CO2 and ethanol, and involves the enzymes pyruvate decarboxylase and alcohol dehydrogenase.

Respiration

• Occurs in the mitochondria and has a high energy yield.
• Three steps involved:
  • Pyruvate Dehydrogenase: Pyruvate is oxidatively decarboxylated, releasing CO2, and forming acetyl CoA.
  • Citric Acid Cycle: Acetyl CoA is metabolized to CO2 and high-energy electron carriers.
  • Oxidative Phosphorylation: Electron carriers transfer electrons to the electron transport chain, generating ATP.

Pyruvate Dehydrogenase Complex

• Consists of three types of enzymatic subunits: E1, E2, and E3.
• Interacts with five B vitamin-derived coenzymes: Thiamine pyrophosphate (TPP), lipoamide, FAD, Coenzyme A, and NAD+.
• Converts pyruvate to acetyl CoA through oxidative decarboxylation, releasing CO2 and generating NADH.

Hangover Biochemistry

• Excessive alcohol intake overwhelms the detoxification system.
• Alcohol is metabolized by alcohol dehydrogenase and aldehyde dehydrogenase, producing acetate.
• Accumulation of acetaldehyde, the toxic intermediate, causes hangover symptoms.

Understand the process of glycolysis, its products, and how pyruvate can be further metabolized through fermentation or respiration. Learn about the two types of fermentation and their key enzymes.