Lecture Notes: Cellular Respiration, Fermentation, and Photosynthesis

Overview

• Discussion on cellular respiration, fermentation, and a bit of photosynthesis.
• Focus on the citric acid cycle (Krebs cycle).

Citric Acid Cycle (Krebs Cycle)

• Originally known as Krebs cycle, now called citric acid cycle.
• Named after the first molecule formed: Citrate.
• Acetyl CoA:
  • Comes from the intermediate step.
  • Contains two carbons.
  • Combines with oxaloacetate (four carbons) to form citrate (six carbons).
  • Releases CO2, NAD+ becomes NADH (reduction).
  • Cycle continues to convert citrate to various molecules, releasing energy.
• Key Processes:
  • Reduction and oxidation (redox reactions) occur throughout the cycle.
  • Produces NADH, FADH2, and some ATP.
  • Cycle regenerates oxaloacetate to repeat the process.

Simplified Citric Acid Cycle

• Two versions of diagrams to simplify understanding.
• Highlights the reactants and products.
• Importance of understanding reactants and products:
  • Two acetyl CoAs from glucose through glycolysis.
  • Results in two cycles per glucose molecule.

Oxidative Phosphorylation

• Occurs in mitochondria, involving inner membrane structures.
• Key Concepts:
  • Electron Transport Chain (ETC): Electrons transferred through proteins, creating a hydrogen ion gradient.
  • Final electron acceptor: Oxygen, forms water.
  • Chemiosmosis: Hydrogen ions flow through ATP synthase to produce ATP.
• Importance:
  • Main source of ATP production.
  • Facilitates conversion of electron carriers (e.g., NADH, FADH2) into ATP.

Cellular Respiration Overview

• Glycolysis in cytosol, leading to pyruvate formation.
• Pyruvate processed through citric acid cycle.
• Electron carriers used in oxidative phosphorylation.
• Substrate-Level Phosphorylation:
  • Enzyme-mediated ATP production in glycolysis and citric acid cycle.

Impact of Poisons on Oxidative Phosphorylation

• Various poisons can affect the electron transport chain and ATP production:
  • Rhodanone: Affects first protein in ETC, blocks gradient formation.
  • Cyanide/Carbon Monoxide: Affects final protein, blocking electron transfer to oxygen.
  • Oligomycin: Inhibits ATP synthase.
  • DNP: Disrupts membrane integrity, preventing gradient formation.
• Understanding these impacts can explain organismal failure in energy production.

Conclusion

• Cellular respiration culminates in ATP production from glucose.
• Key processes: Glycolysis, citric acid cycle, oxidative phosphorylation.
• Importance of understanding reactions and impacts on physiological functions.

Note: Review textbook diagrams for visual understanding, especially for test preparations.