Respiration Lecture Notes

Overview

• Focus: Comprehensive coverage of respiration for Unit 2
• Key Topics:
  • Glycolysis
  • Link Reaction
  • Krebs Cycle
  • Electron Transport Chain
  • Anaerobic Respiration
  • Experiment to measure respiration rate

Glycolysis

• Location: Cytoplasm of the cell
• Process:
  • Glucose enters the cell via diffusion
  • Conversion: Glucose → Glucose 6-phosphate → Fructose 1,6-bisphosphate
  • Phosphorylation: Uses 2 ATP (ATP → ADP)
  • Lysis: Fructose 1,6-bisphosphate splits into two triose phosphates
  • Oxidation: Triose phosphate oxidized to an intermediate compound; NAD reduced to NADH
  • Substrate-level Phosphorylation: Forms 4 ATP (net gain of 2 ATP)
• End Products:
  • 2 ATP (net)
  • 2 NADH
  • 2 Pyruvate

Link Reaction

• Conversion: Pyruvate + Coenzyme A + NAD → Acetyl Coenzyme A + NADH + CO2
• Products per Glucose:
  • 2 NADH
  • 2 Acetyl Coenzyme A

Krebs Cycle

• Location: Mitochondrial Matrix
• Process:
  • Acetyl Coenzyme A + Oxaloacetate → Citrate (6-carbon compound)
  • Citrate → Isocitrate
  • Decarboxylation & Dehydrogenation: Isocitrate → Alpha-ketoglutarate
  • Produces: CO2, NADH
  • Alpha-ketoglutarate → Succinyl Coenzyme A (similar reactions continue)
  • Substrate-level Phosphorylation: Succinyl Coenzyme A → Succinate (produces ATP)
  • Succinate → Fumarate (oxidation using FAD)
  • Fumarate → Malate (addition of water)
  • Malate → Oxaloacetate (produces NADH)
• Yield per Glucose:
  • 6 NADH
  • 2 FADH2
  • 2 ATP

Electron Transport Chain (ETC)

• Process:
  • High-energy electrons from NADH & FADH2 pass through electron carriers
  • Energy released forms ATP
  • Ends with electrons combining with O2 to form water
• ATP Yield:
  • 1 NADH → 3 ATP
  • 1 FADH2 → 2 ATP

Total ATP Yield in Aerobic Respiration

• Glycolysis: 2 ATP (net), 2 NADH
• Link Reaction: 2 NADH
• Krebs Cycle: 6 NADH, 2 FADH2, 2 ATP
• ETC:
  • 10 NADH × 3 ATP = 30 ATP
  • 2 FADH2 × 2 ATP = 4 ATP
• Total: 38 ATP per glucose molecule

Anaerobic Respiration

• Occurs without Oxygen
• Process: Only Glycolysis
  • Produces 2 ATP per glucose
  • Regeneration of NAD by converting pyruvate to either:
    • Ethanol + CO2 (in yeast) [Alcoholic Fermentation]
    • Lactic Acid (in animals) [Lactic Acid Fermentation]

Experiment to Measure Respiration Rate

• Apparatus:
  • Ruler with a liquid droplet
  • Soda lime to absorb CO2
  • Organism chamber
• Procedure:
  • Oxygen consumption pulls the droplet (measured to calculate rate)
  • Soda lime prevents CO2 from affecting droplet movement

Conclusion

• Respiration: Complex process providing energy
• Key Points: Understand pathways, enzyme roles, and ATP yield calculations
• Experiment: Demonstrates practical measurement of respiration rate.