Metabolism and Cellular Respiration Overview

Introduction

• Focus on where energy comes from in major areas of metabolism and cellular respiration.
• Steps and pathways to be discussed later.

Glycolysis: "The Big Picture"

• Process:
  • Start with one six-carbon glucose molecule.
  • Split into two three-carbon pyruvates.
  • Net gain of 2 ATP (use 2 ATP to produce 4 ATP).
• Energy Produced:
  • 2 ATP ("money in hand").
  • 2 NADH ("casino chips," each worth 3 ATP).
• Total Potential:
  • 2 ATP + potential for 6 more ATP from NADH (via electron transport system).

Intermediate Step

• Process:
  • Convert two three-carbon pyruvates into two-carbon acetyl CoA.
• Energy Produced:
  • 0 ATP produced.
  • 2 additional NADH.
• Total Potential:
  • 2 ATP + 4 NADH (potential for 12 more ATP).

Krebs Cycle (Citric Acid Cycle/TCA Cycle)

• Process:
  • Must go through the cycle twice (due to splitting glucose in half).
  • Generates 2 ATP in total (1 ATP per cycle run).
• Electron Carriers Produced:
  • 6 NADH (worth 18 ATP).
  • 2 FADH2 (worth 4 ATP).
• Total Energy Potential Post-Krebs Cycle:
  • 4 ATP (actual) + 10 NADH (worth 30 ATP) + 2 FADH2 (worth 4 ATP).

Electron Transport System (Cashier)

• Process:
  • Total potential ATP from electron carriers.
  • 10 NADH = 30 ATP.
  • 2 FADH2 = 4 ATP.
  • Additional 34 ATP generated.
• Summary:
  • 2 ATP from Glycolysis.
  • 0 ATP from Intermediate Step.
  • 2 ATP from Krebs Cycle.

Total Energy Production

• Prokaryotes (Bacteria):
  • Maximum ATP yield: 38 ATP (if fully oxidizing glucose).
• Eukaryotes (Humans):
  • Maximum ATP yield: 36 ATP.
  • Reason for Difference:
    • 2 ATP used for NADH transport into mitochondria.
    • Mitochondria as the powerhouse (95% of ATP production).

Conclusion

• This lecture outlines where the energy comes from during cellular respiration.
• Future videos will delve deeper into the processes and pathways.
• Reminder: Actual yield may vary; theoretical yield discussed is a textbook example.