The Oxidative Energy System - Carbohydrate

The Oxidative Energy System: Carbohydrate

Overview of the Oxidative System

  • Aerobic Process: Utilizes oxygen for energy production

  • ATP Yield:

    • 32 to 33 ATP produced per molecule of glucose

    • More than 100 ATP produced per fatty acid (FFA)

  • Duration: Supplies energy steadily for hours

  • Complexity: Considered the most complex of the three bioenergetic systems

  • Location: Occurs in mitochondria, not the cytoplasm

Oxidation of Carbohydrate

Stages of Oxidation

  1. Glycolysis: Breaks down glucose into pyruvate

  2. Krebs Cycle: Further processes acetyl-CoA from glycolysis

  3. Electron Transport Chain (ETC): Produces the majority of ATP

Glycolysis

Process and Output

  • Location: Occurs in the cytosol

  • Input: 1 Glucose molecule

  • Outputs:

    • 2 ATP produced (net)

    • 2 NADH + H+

    • 2 Pyruvate molecules

Anaerobic vs. Aerobic Glycolysis

  • Glycolysis can occur with or without oxygen.

  • Yield is the same for both aerobic and anaerobic glycolysis.

  • In the presence of oxygen, pyruvic acid is converted to acetyl-CoA, which enters the Krebs cycle.

Krebs Cycle

Overview

  • Input: 2 Acetyl-CoA from 1 Glucose molecule

  • Outputs:

    • 2 complete Krebs cycles per glucose

    • 2 GTP (equivalent to ATP)

    • NADH and FADH2 produced

  • Acidity Regulation: Excess H+ can make the cell too acidic; H+ is transferred to the electron transport chain.

Importance of Acetyl-CoA

  • Contribution: Acetyl-CoA is crucial for the Krebs cycle, enhancing ATP yield and energy production.

Electron Transport Chain (ETC)

Function and Process

  • H+ and Electrons: Carried to the ETC via NADH and FADH2

  • Oxygen Role: Combines with H+ to form water (H2O)

  • ATP Formation: Electrons help in ATP synthesis

  • ATP Yield:

    • 2.5 ATP produced per NADH

    • 1.5 ATP produced per FADH2

Energy Yield from Carbohydrates

  • Total Yield:

    • 1 glucose = 32 ATP

    • 1 glycogen = 33 ATP

  • Breakdown of Totals:

    • Glycolysis: +2 ATP (or +3)

    • Krebs Cycle: +2 ATP (GTP)

    • 10 NADH: +25 ATP

    • 2 FADH2: +3 ATP

Mitochondrial Dynamics

Structure and Function

  • Outer Mitochondrial Membrane: Site for various transport processes

  • Inner Mitochondrial Membrane:

    • Location for majority of the electron transport and ATP synthesis

    • H+ ions buildup leads to ATP production via ATP synthase

ATP and the Mitochondria

  • Each NADH results in 2.5 ATP due to the transport across the mitochondrial membranes.

  • Each FADH2 results in 1.5 ATP.

Summary of ATP Yield

Phosphorylation Processes

  • Substrate-level phosphorylation: Direct ATP generation from a reaction (e.g., Krebs cycle)

  • Oxidative phosphorylation: ATP generation through the electron transport chain

Total ATP Yield Calculation

  1. Glycolysis: 2 ATP (net after initial investment)

  2. Krebs Cycle: Additional ATP from GTP

  3. Electron transport: Contributions from NADH and FADH2 accumulation

  4. Final Yield: Total energy yield across the system = 32 ATP per glucose.