Fatty Acid Oxidation Study Notes

Overview of Fatty Acid Oxidation

  • Fatty acid oxidation is a metabolic process crucial for converting stored fats into energy.

  • Prior knowledge of fat immobilization (triglyceride breakdown into components) is helpful for understanding this process.

Import and Utilization of Fatty Acids

  • Tissue utilization of fatty acids for energy:

    • Heart muscle (myocardium)

    • Skeletal muscles

    • Liver

  • The liver is particularly important as it generates ketone bodies from fatty acids.

Entry of Fatty Acids into Cells

  • Fatty acids are transported into tissue cells for energy production.

  • Example used: Long-chain fatty acids (around 16 carbons), e.g., palmitoleic acid.

Structure of Fatty Acids

  • Key structural features:

    • Carboxylate group

    • Alpha carbon and beta carbon are adjacent to the carboxylate group.

  • Fatty acids to be activated within the cell to prevent them from exiting.

Activation of Fatty Acids

  • Enzyme Involved: Fatty acyl CoA synthetase

  • Process:

    • Fatty acid is converted to fatty acyl CoA using ATP:

    • Reaction: Fatty acid + CoA + ATP → Fatty acyl CoA + ADP + Pi

    • Energy is consumed in the form of ATP breakdown.

  • Result: Formation of fatty acyl CoA ready for transport into mitochondria.

Transport of Fatty Acyl-CoA to the Mitochondria

  • Transport Mechanism:

    • Fatty acyl CoA cannot enter mitochondria directly due to CoA.

    • It is combined with carnitine through a translocase enzyme, yielding fatty acyl carnitine:

    • Formulation: Fatty acyl CoA + Carnitine → Fatty acyl carnitine + CoA

    • Fatty acyl carnitine can now be transported across mitochondrial membrane.

  • Inside the Mitochondria:

    • Fatty acyl carn iteration is converted back to fatty acyl CoA via the action of carnitine acyltransferase type II.

    • Formula: Fatty acyl carnitine + CoA → Fatty acyl CoA + Carnitine

Beta-Oxidation of Fatty Acids

  • This is the crucial metabolic process occurring in the mitochondria to generate energy from fatty acids.

  • Steps of Beta-Oxidation

    1. Dehydrogenation:

    • FAD removes hydrogen from fatty acyl CoA, forming trans delta-2 enoyl CoA.

    • Enzyme: Acyl CoA dehydrogenase

    1. Hydration:

    • Water is added across double bond.

    • Enzyme: Enoyl CoA hydratase

    • Product: Beta-hydroxyacyl CoA

    1. NAD+ Reduction:

    • Beta-hydroxyacyl CoA is oxidized to beta-ketoacyl CoA while NAD+ is reduced to NADH.

    • Enzyme: Beta-ketoacyl CoA dehydrogenase

    1. Thiolysis:

    • Bond between alpha and beta carbon is cleaved to release acetyl CoA and a new fatty acyl CoA.

    • Enzyme: Thiolase

  • Each cycle of beta oxidation shortens the fatty acid chain by two carbons, producing one molecule of acetyl CoA and a new fatty acyl CoA.

Summary of Beta-Oxidation Cycle

  • A 16-carbon fatty acid undergoes seven cycles of beta-oxidation:

    • Produces 8 molecules of acetyl CoA (one for every two carbons).

    • NADH and FADH2 are also generated at various steps, contributing to ATP production through the electron transport chain.

  • Energy Yield Considerations:

    • Detailed calculations of ATP yield from oxidation of fatty acids to be discussed in later materials.

Conclusion and Further Topics

  • Fatty acid oxidation serves as a crucial energy source when carbohydrates are not available.

  • Next topics will address energy yield calculations, odd-chain fatty acids, and peroxisomal beta oxidation processes.