Chapter 3 - PART B - Glycolysis - Intermediate - Krebs

Overview of Cellular Respiration

  • Cellular respiration involves burning glucose (C6H12O6) in the presence of oxygen (O2).

  • Main purpose: To oxidize glucose into byproducts of carbon dioxide (CO2), water (H2O), and ATP (energy).

  • Chemical Equations:

    • C6H12O6 + 6O2 → 6CO2 + 6H2O + Heat + 38 ATP

Energy Production

  • Total of 38 ATP produced from each glucose molecule in cellular respiration.

  • Process generates heat, maintaining body temperature around 98.6°F.

Structure of the Cell

  • Key organelles involved:

    • Mitochondrion: Main site of ATP production.

      • Outer double-walled plasma membrane protects the organelle.

      • Cytoplasm: where initial glycolysis occurs.

Stages of Cellular Respiration

  • Four main stages:

    1. Glycolysis (occurs in the cytoplasm)

    2. Intermediate stage (occurs in mitochondrion)

    3. Citric acid cycle (Krebs cycle, occurs in mitochondrion)

    4. Electron transport chain (occurs in mitochondrion)

Stage 1: Glycolysis

  • Location: Cytoplasm

  • Process:

    • One glucose molecule (6 carbons) splits into two pyruvate molecules (3 carbons each).

    • Generates 2 ATP and 2 NADH.

    • Anaerobic Process: Does not require oxygen.

  • Enzyme involvement: 10 specific enzymes control the reactions of glycolysis.

Stage 2: Intermediate Stage

  • Location: Mitochondrion

  • **Process:"

    • Pyruvate is converted into Acetyl CoA (2 carbons).

    • One carbon is removed as CO2 during this transition.

    • Requires oxygen.

    • Specific enzyme: Pyruvate dehydrogenase.

Stage 3: Citric Acid Cycle (Krebs Cycle)

  • Location: Mitochondrion

  • Process:

    • Acetyl CoA enters and undergoes a series of reactions, producing:

      • 2 ATP

      • 3 NADH per pyruvic acid

      • 1 FADH2 per pyruvic acid

      • 3 CO2 per pyruvic acid

    • Combines the breaking down of pyruvate into CO2 and captures energy.

  • Total of 20 enzymes used in glycolysis, intermediate stage, and Krebs cycle combined.

Stage 4: Electron Transport Chain (ETC)

  • Location: Mitochondrion

  • Purpose:

    • Primary site for ATP production, generating 34 ATP mostly via oxidative phosphorylation.

  • Involves transferring electrons from NADH and FADH2 to create a proton gradient that drives ATP synthesis.

Importance of Enzymes

  • Enzymes act as catalysts, controlling each step of cellular respiration.

  • Specific enzymes required for each chemical reaction, facilitating breakdown of glucose in a controlled manner.

  • Example: Enzymes for glycolysis are distinct and do not work with reactions in Krebs cycle.

Conclusion

  • Cellular respiration is a tightly controlled process that allows for efficient energy extraction from glucose, crucial for all cellular processes.

  • Maintaining low heat production is essential, as excessive heat can damage tissues.