Lecture Notes: Cellular Respiration and Fermentation

Overview

• Chapter 9, Part 2
• Topics: Glycolysis, Pyruvate Processing, Citric Acid Cycle (Krebs Cycle), Electron Transport Chain (ETC), Fermentation

Glycolysis

• Location: Cytosol
• Input: Glucose
• Output:
  • 2 Pyruvate
  • 2 NADH
  • 2 ATP (Net)
• ATP Production Method: Substrate-level phosphorylation

Pyruvate Processing

• Location: Mitochondrial matrix
• Input: Pyruvate
• Output:
  • 2 Acetyl CoA
  • 2 NADH
  • 2 CO2
• ATP Production: None

Citric Acid Cycle (Krebs Cycle)

• Location: Mitochondrial matrix
• Input: Acetyl CoA
• Output:
  • 6 NADH
  • 2 FADH2
  • 4 CO2
  • 2 ATP/GTP
• ATP Production Method: Substrate-level phosphorylation

Electron Transport Chain (ETC) and Oxidative Phosphorylation

• Location: Inner mitochondrial membrane
• Process: Transfer electrons from NADH and FADH2 through a series of complexes
• Important Components:
  • Ubiquinone (Coenzyme Q): Lipid-soluble, non-protein component of ETC
  • Cytochrome C
• Proton Gradient: Protons (H+) pumped into the intermembrane space
• ATP Production: Proton flow through ATP synthase
  • Converts ADP + Pi to ATP
  • Total ATP yield from ETC: ~26 ATP

Summary of Cellular Respiration ATP Yield

• Glycolysis: 2 ATP
• Citric Acid Cycle: 2 ATP
• ETC: ~26 ATP
• Total: ~30 ATP per glucose molecule

Fermentation

• Purpose: Regenerate NAD+ in the absence of oxygen
• Types:
  • Lactic Acid Fermentation: Produces lactate
  • Alcohol Fermentation: Produces ethanol and CO2
• ATP Yield:
  • Only 2 ATP per glucose (from glycolysis)

Key Concepts

• Energy Transfer in Respiration: Sequential, small steps to prevent cell damage

  • Glycolysis: Cytosol, produces pyruvate, 2 NADH, 2 ATP
  • Pyruvate Processing: Mitochondrial matrix, produces Acetyl CoA, 2 NADH, 2 CO2
  • Citric Acid Cycle: Mitochondrial matrix, produces 6 NADH, 2 FADH2, 4 CO2, 2 ATP/GTP
  • ETC: Inner mitochondrial membrane, uses proton gradient to produce ~26 ATP

• **Oxidative vs. Substrate-Level Phosphorylation: **

  • Substrate-Level: Direct transfer of phosphate (Glycolysis, Citric Acid Cycle)
  • Oxidative: ATP synthase driven by proton gradient (ETC)

• Anaerobic vs. Aerobic Metabolism:

  • Aerobic Respiration: Oxygen as final electron acceptor, high ATP yield
  • Anaerobic Respiration: Other electron acceptors, lower ATP yield
  • Fermentation: Regenerates NAD+, low ATP yield

Conclusion

• Importance of Memorization: Know locations, inputs, outputs, and ATP production methods
• Exam Tips: Focus on what goes in and out, where processes occur, and how ATP is produced
• Final Note: A comprehensive understanding of these stages is critical for mastering cellular respiration and fermentation.