In peroxisomal beta-oxidation, which structural class of fatty acids is EXCLUSIVELY oxidized in peroxisomes and cannot be handled by mitochondrial beta-oxidation?

• A Medium-chain fatty acids (C8–C12)
• B Odd-chain fatty acids producing propionyl-CoA
• C Saturated long-chain fatty acids (C16–C18)
• D Very long-chain fatty acids (VLCFA, >C22) and branched-chain fatty acids (phytanic acid) ✓

Explanation

Peroxisomal beta-oxidation is essential for: (1) very long-chain fatty acids (VLCFAs, >C22 — e.g., C24:0, C26:0), which cannot enter mitochondria via the carnitine transport system; (2) branched-chain fatty acids such as phytanic acid (requires peroxisomal alpha-oxidation to pristanic acid first, then beta-oxidation). In Zellweger syndrome (peroxisome biogenesis disorder) and X-linked adrenoleukodystrophy (ALD, ABCD1 transporter defect), VLCFA accumulation causes demyelination and adrenal insufficiency. Mitochondria handle long-chain (C16–C18), medium-chain, and odd-chain fatty acids. Peroxisomes produce acetyl-CoA and shorter acyl-CoA that are exported to mitochondria.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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