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Chapter6

Chapter 6: Fermentation and Respiration

1. Overview of Energy Metabolism

  • Cellular metabolism during exercise requires energy, primarily from glucose.

  • Two types of metabolism:

    • Aerobic Metabolism

      • Requires sufficient oxygen for complete glucose breakdown.

    • Anaerobic Metabolism

      • Occurs when oxygen is limited; glucose is partially broken down.

2. Cellular Respiration Basics

  • Cellular Respiration: The process where potential energy in organic molecules is converted into usable energy (ATP) for the cell.

    • Involves aerobic processes requiring oxygen.

3. Gas Exchange and Cellular Respiration

  • Gas exchange occurs in lungs through breathing:

    • Oxygen is inhaled; carbon dioxide (CO2) is expelled.

  • Equation: Glucose + O2 → CO2 + H2O + ATP

4. Importance of Glucose in Cellular Respiration

  • Glucose (monosaccharide) is the main fuel for cellular respiration, yielding CO2 and H2O when oxidized in the presence of oxygen.

  • The overall reaction indicates the breakdown of glucose into energy:

    • Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)

5. The Role of Oxygen

  • Oxygen is critical in cellular respiration, facilitating the transfer of hydrogen atoms and electrons from glucose, leading to water production.

  • Oxidation: The removal of electrons from a molecule, freeing energy in the process.

6. Redox Reactions in Respiration

  • Redox Reactions: Involving transfer of electrons between molecules.

    • Oxidation: Electron loss (reducing agent).

    • Reduction: Electron gain (oxidizing agent).

  • Energy release occurs as electrons transition to a lower energy state, akin to descending an energy hill.

7. Metabolic Pathways in Cellular Respiration

  • Cellular respiration is a metabolic pathway with three stages:

    • Glycolysis

    • Krebs Cycle (Citric Acid Cycle)

    • Electron Transport Chain

8. Glycolysis

  • Stage 1: Glycolysis

    • Converts glucose into two molecules of pyruvic acid.

    • Involves NAD+ conversion to NADH and ATP production via substrate-level phosphorylation.

    • Products: 2 Pyruvate, 2 NADH, and a net gain of 2 ATP.

9. Krebs Cycle (Citric Acid Cycle)

  • Stage 2: Krebs Cycle

    • Pyruvic acid is oxidized to acetyl CoA and enters the cycle.

    • Produces ATP directly, alongside NADH and FADH2 as electron carriers, while releasing CO2.

10. Electron Transport Chain (ETC)

  • Stage 3: Electron Transport Chain

    • Electrons from NADH and FADH2 are transferred through a series of acceptors, creating a proton gradient across the mitochondrial membrane.

    • Protons flow through ATP synthase, driving the conversion of ADP and P into ATP (chemiosmosis).

    • Approximately 28-34 ATP produced from oxidative phosphorylation.

11. Fermentation

  • Fermentation: Under anaerobic conditions, cells can metabolize glucose without oxygen, yielding ATP.

    • Lactic Acid Fermentation in human muscle cells leads to muscle fatigue due to lactic acid buildup.

    • Alcoholic Fermentation occurs in yeast, producing CO2 and ethanol, useful in baking and brewing.

12. Differences in Muscle Fiber Types

  • Type I Fibers:

    • Aerobic metabolism, sustain long-term activity (endurance).

    • Common in long-distance runners.

  • Type II Fibers:

    • Anaerobic metabolism, suited for short bursts of activity.

    • Common in sprinters, characterized by quick contractions.