Chapter 7 Study Notes

Chapter Seven Study Notes

Overview of Topics

• Due Dates:

  • Chapter tests and quizzes.

  • Homework completion suggested before tests to clarify questions.

Metabolism of Glucose

• Principles of Glucose Breakdown:

  • Glucose is a primary source of ATP.

  • Two major processes for glucose breakdown: Cellular Respiration and Fermentation.

Types of Cellular Respiration

• Aerobic Respiration:

  • Requires oxygen (O₂).

  • Oxygen constitutes 20-21% of molecular air.

• Anaerobic Respiration:

  • Does not require oxygen.

  • Each of these processes has distinct characteristics.

Summary Comparison of Glucose Breakdown Processes

• Aerobic vs Anaerobic Respiration:

  • Aerobic:

  • Requires O₂.

  • Uses both substrate-level and oxidative phosphorylation.

  • Anaerobic:

  • Does not use O₂.

  • Final electron acceptors can vary (nitrates, sulfates, carbonates).

  • Generates ATP through both substrate-level and oxidative phosphorylation.

• Fermentation:

  • Similar to anaerobic but uniquely characterized by using organic molecules as final electron acceptors.

  • Generates ATP only through substrate-level phosphorylation.

ATP Yield from Processes

• Aerobic Respiration:

  • Theoretical yield of ATP:

  • Eukaryotes: 36 ATP

  • Prokaryotes: 38 ATP

• Anaerobic Respiration:

  • Varying yields primarily depending on bacterial type (2 to 36 ATP).

• Fermentation:

  • Fixed yield of 2 ATP per glucose molecule:

  • By-products: Often lactic acid or ethanol.

Summary of Final Electron Acceptors

• Aerobic Respiration: O₂

• Anaerobic Respiration: Nitrates, sulfates, carbonates

• Fermentation: Endogenous organic molecules

Stages of Aerobic Cellular Respiration

1. Glycolysis

2. Pyruvate Oxidation (Transition Step)

3. Citric Acid Cycle (Krebs Cycle)

4. Electron Transport Chain and Chemiosmosis

Stage One: Glycolysis

• Location:

  • Eukaryotes: Cytosol

  • Prokaryotes: Cytosol

• Summary of Glycolysis:

  • Overall equation involves breaking glucose (6-carbon) into two pyruvate molecules (3-carbon each).

  • Occurs through a series of 10 reactions.

• Key Products:

  • 2 Pyruvic Acid molecules

  • 2 NADH (carrying energy)

  • Net gain of 2 ATP (4 produced, 2 used)

• Phosphorylation Types in Glycolysis:

  • Substrate-level Phosphorylation: Only type present in glycolysis.

Stage Two: Pyruvate Oxidation

• Location:

  • Eukaryotes: Matrix of mitochondria

  • Prokaryotes: Cytosol

• Process:

  • One carbon atom removed from pyruvate (decarboxylation), producing carbon dioxide.

  • Remaining 2-carbon molecule (acetyl CoA) is formed; reduced NADH is produced.

  • Products: 2 Acetyl CoA, 2 NADH, 2 CO₂

Stage Three: Citric Acid Cycle (Krebs Cycle)

• Location:

  • Eukaryotes: Matrix of mitochondria

  • Prokaryotes: Cytosol

• Process:

  • Acetyl CoA enters the cycle and undergoes a series of reactions, releasing all carbon as CO₂.

  • Consists of 8 steps, producing energy carriers:

  • Products per 2 Acetyl CoA:

    • 4 CO₂

    • 6 NADH

    • 2 FADH₂

    • 2 ATP (via substrate-level phosphorylation)

Stage Four: Electron Transport Chain and Chemiosmosis

• Location:

  • Eukaryotes: Inner mitochondrial membrane (cristae)

  • Prokaryotes: Plasma membrane

• Process:

  • NADH and FADH₂ donate electrons to various complexes of the electron transport system (complexes I-IV).

  • As electrons pass, protons (H⁺) are pumped out, creating a gradient (proton motive force).

• ATP Synthesis:

  • Protons flow back through ATP synthase, driving ATP production via oxidative phosphorylation.

  • Yield: 3 ATP per NADH and 2 ATP per FADH₂.

• Theoretical Total Yield:

  • For 1 glucose:

  • 36 ATP in eukaryotes

  • 38 ATP in prokaryotes

Final Considerations

• Oxygen is the final electron acceptor; it reacts with protons to form water, which is crucial in aerobic respiration.

Study Strategies

• Familiarize with the overall processes and their locations.

• Understand the differences in ATP generation from aerobic respiration, anaerobic respiration, and fermentation.

• Use diagrams to visualize glycolysis, the Krebs cycle, and the electron transport chain.