Key Concepts in Cellular Respiration

Overview of Glycolysis

• Glucose (6-carbon molecule): Split in half during glycolysis
• Products: 2 pyruvate (3-carbon molecules)
• Occurs in: Cytoplasm
• Oxygen Requirement: Can occur with or without oxygen
• ATP Yield: Net gain of 2 ATP (4 produced, 2 used)
• NADH Produced: 2 NADH

Structure of a Cell

• Cell Components: Outer membrane, nucleus, organelles
• Cytoplasm: Fluid space where glycolysis occurs
• Mitochondria: Power center of the cell with outer/inner membranes (cristae)

Transition to Krebs Cycle

• Location: Inner space of mitochondria (matrix)
• Pyruvate Oxidation: Prepares pyruvate for the Krebs cycle by oxidizing it into acetyl-CoA (2-carbon compound)
• NADH Produced: Additional NADH during pyruvate oxidation

Krebs Cycle (Citric Acid Cycle)

• Process: Enzyme-catalyzed reactions
• Reactants: Acetyl-CoA merges with oxaloacetic acid (4-carbon)
• Product: Citrate (6-carbon molecule oxidized back to oxaloacetic acid)
• By-products: Carbon dioxide (CO2) is produced
• Energy Carriers Produced:
  • NADH and FADH2
  • ATP

Overall ATP Production

• Glycolysis: 2 ATP, 2 NADH
• Krebs Cycle:
  • 6 NADH, 2 ATP, 2 FADH2 (per glucose molecule)
  • Pyruvate oxidation adds 2 NADH
• Total ATP through Electron Transport Chain:
  • NADH: 30 ATP (10 NADH x 3 ATP each)
  • FADH2: 4 ATP (2 FADH2 x 2 ATP each)
  • Theoretical Maximum: 38 ATP in efficient cells

Other Metabolic Pathways

• Alternative Fuels: Proteins & Fats
  • Proteins can be broken into amino acids -> acetyl-CoA
  • Fats can be converted to glucose
• Acetyl-CoA: Entry point for other catabolic pathways into Krebs Cycle

Conclusion

• Diagram Reference: Confirms enzymatic steps and product yields
• Key Takeaways:
  • Understand steps and yields from glycolysis, pyruvate oxidation, and the Krebs cycle
  • Recognize the role of electron carriers NADH and FADH2 in ATP production
  • Appreciate the flexibility of cellular respiration in metabolizing various nutrients