Beta Oxidation of Fatty Acids

Introduction

• Beta oxidation is a catabolic pathway where free fatty acids are converted to acyl-CoA.
• It involves oxygen, hence termed "oxidation".
• Named "beta oxidation" because the R chain of the fatty acid is broken down between the alpha and beta carbons.

Structure of Fatty Acids

• Major storage form of fats: triglycerides.
• Triglycerides consist of glycerol attached to three fatty acids.
• Fatty acids have a long chain of carbon and hydrogen (R) and a carboxylic group.
• Alpha Carbon: Directly attached to the functional group.
• Beta Carbon: Adjacent to the alpha carbon.

Overview of Beta Oxidation Process

• Adipose Tissue: Stores triglycerides.
• Distribution: Fatty acids distributed through blood to cells that can metabolize them.
• Cell Entry: Fatty acids move into the cytoplasm and then into mitochondria.
• Oxidative Catabolism: Occurs inside the mitochondrial matrix.

Phases of Beta Oxidation

A. Transport of Fatty Acids

• Adipose Cells: Contain triglycerides with glycerol and free fatty acids.
• Lipase Enzyme: Breaks bond between glycerol and fatty acids.
• Free Fatty Acids: Enter bloodstream; reach cells for metabolism.
• RBCs and nervous tissue cannot metabolize fatty acids due to lack of mitochondria.

B. Entry into Cytoplasm and Mitochondria

• Fatty Acid Transporter: Facilitates entry into cell cytoplasm.
• Activation of Fatty Acids: Conversion to acyl-CoA by acetyl-CoA synthetase.
  • Reaction involves ATP, pyrophosphate, and coenzyme A.
  • Activation occurs at outer mitochondrial membrane, ER, and peroxisomes.
• Transport to Mitochondria: Via carnitine shuttle.
• Outer Membrane: Porins allow permeable passage of acyl-CoA.
• Inner Membrane: Requires carnitine shuttle for transport.

C. Carnitine Shuttle Mechanism

• Carnitine Palmitoyltransferase I: Located on outer membrane; attaches carnitine to acyl-CoA.
• Translocase: Transports acyl-carnitine into the Matrix.
• Carnitine Palmitoyltransferase II: Regenerates acyl-CoA inside the Matrix.
• Carnitine Recycling: Transported back to intermembrane space for reuse.

Conclusion

• Discussed transport and entry of fatty acids into mitochondria.
• Next video will cover oxidative catabolism inside the mitochondrial matrix.

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