bio respiration

Chapter 9: Harvesting Energy

Introduction to Respiration

• Definition of Respiration: Involves the process of breathing and breaking down food for energy, specifically ATP.

• Types of Respiration:

  • Aerobic Respiration: Requires oxygen; involves the breakdown of glucose molecules to extract energy.

  • Anaerobic Respiration: Occurs without oxygen; different pathways are utilized for energy extraction.

  • Importance of Oxygen: Serves as the final electron acceptor in aerobic respiration.

Overview of Metabolism

• Primary Fuel Source: Glucose is the primary molecule used for ATP production, but fats, proteins, and nucleic acids can also be utilized.

• Metabolic Pathways: These pathways are interconnected and facilitate the breakdown of various macromolecules for energy.

• Energy Release: The breakdown of glucose yields approximately 686 kilocalories, demonstrating significant energy release during metabolism.

Summary Equation of Respiration

• Chemical Equation:

  • Glucose + Oxygen → Water + Carbon Dioxide + ATP

• Chemical Reactions: Many individual reactions occur within this overarching equation, which we will explore in detail later.

Metabolic Pathways

• Interwoven Pathways: All metabolic pathways, including carbohydrate metabolism, lipid metabolism, and amino acid metabolism, contribute to ATP production.

• Eukaryotes vs. Prokaryotes: Differences in the location of metabolic pathways; eukaryotes utilize organelles, while prokaryotes rely on the cell membrane.

• Redox Reactions: Involves the transfer of electrons, where oxidation is the loss of electrons (oxidizing agent) and reduction is the gain (reducing agent).

Redox Reactions

• Understanding Redox:

  • Oxidation is Loss (OIL)

  • Reduction is Gain (RIG)

• Example Process: Sodium and Chlorine react; sodium gets oxidized (loses an electron) and chlorine gets reduced (gains an electron).

Organic Molecules and Energy

• Examples of Oxidation:

  • Methane oxidizes to form methanol, then formaldehyde, then formic acid, and finally carbon dioxide—showing increasing oxidation.

• Carbon Compounds: Carbon from glucose ends up as carbon dioxide; hydrogen from glucose forms water.

• Final Electron Acceptance: Oxygen serves as the terminal electron acceptor in aerobic respiration.

Role of Electron Carriers

• NAD and FAD:

  • NAD+: Oxidized form; becomes NADH when it gains a hydrogen.

  • FAD: Similarly gains hydrogens to become FADH2.

• Function: Carry electrons through metabolic pathways to facilitate ATP generation.

Efficiency of Metabolic Pathways

• Controlled Energy Release: Metabolism operates through controlled steps, increasing efficiency in energy extraction.

• Analogy of Gas Tank: Comparisons drawn between the efficiency of car engines and metabolic pathways, emphasizing controlled reactions over combustion.

Stages of Harvesting Energy from Glucose

1. Glycolysis: Conversion of glucose into two molecules of pyruvate.

2. Krebs Cycle: Further breakdown of products to release more energy.

3. Oxidative Phosphorylation: Comprises the electron transport chain and chemiosmosis, where most ATP is produced.

Conclusion

• Preview of Next Topics: Next lessons will focus on the detailed processes in glycolysis, Krebs cycle, and oxidative phosphorylation.