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Fermentation Pathways Comparison

Run the Fermentation Pathways Comparison MicroSim Fullscreen

About This MicroSim

This interactive step-through diagram compares lactic acid fermentation and alcoholic fermentation side by side. Both pathways begin with glycolysis and regenerate NAD+ to keep glycolysis running when oxygen is unavailable. The left panel traces pyruvate to lactate (muscle cells, Lactobacillus), while the right panel traces pyruvate through acetaldehyde to ethanol + CO2 (yeast, waterlogged plants). A central column highlights the shared purpose: NAD+ regeneration.

How to Use

  1. Click Next Step to advance through the 8-step narration
  2. Use Start Simulation to auto-advance at an adjustable delay
  3. Switch Pathway Focus to highlight one pathway or both
  4. Toggle Oxygen Mode between anaerobic (fermentation essential) and aerobic (ETC active)
  5. Click organism icons at the bottom of each panel for fun facts
  6. Watch the progress bar and highlighted path segments trace molecule flow

Key Concepts

  • Both fermentation types produce only 2 ATP per glucose (from glycolysis alone)
  • Fermentation does not produce additional ATP — its purpose is to regenerate NAD+
  • Lactic acid fermentation: pyruvate + NADH -> lactate + NAD+
  • Alcoholic fermentation: pyruvate -> acetaldehyde + CO2, then acetaldehyde + NADH -> ethanol + NAD+
  • Without NAD+ recycling, glycolysis would halt and no ATP could be made

Lesson Plan

Grade Level

9-12 (college placement Biology)

Duration

10-15 minutes

Prerequisites

  • Glycolysis (reactants, products, ATP yield)
  • Role of NAD+/NADH as electron carriers
  • Concept of anaerobic vs aerobic conditions

Activities

  1. Step-through (5 min): Students advance through all 8 steps, reading each narration and tracking where NADH is oxidized
  2. Comparison (5 min): Students switch between pathway focus modes and identify similarities and differences
  3. Assessment (5 min): Students answer: "Why is NAD+ regeneration the real purpose of fermentation, not ATP production?"

Assessment

  • Can students explain why both pathways yield only 2 ATP per glucose?
  • Can students identify the waste products of each pathway?
  • Can students explain why fermentation is necessary when oxygen is absent?

References

  1. Fermentation - Wikipedia
  2. Lactic acid fermentation - Wikipedia
  3. Ethanol fermentation - Wikipedia
  4. Glycolysis - Wikipedia
  5. NAD+ - Wikipedia