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Concept Breakdowns

Beta-Oxidation of Fatty Acids Step by Step

Beta-oxidation breaks down fatty acids into acetyl-CoA in the mitochondrial matrix. Understanding each enzymatic step is essential for USMLE Step 1 and biochemistry coursework, particularly for diagnosing fatty acid oxidation disorders and interpreting clinical enzyme deficiencies.

Interactive Deck

5 Cards
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Front

What is beta-oxidation?

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Beta-oxidation: Mitochondrial pathway that sequentially cleaves 2-carbon acetyl-CoA units from fatty acyl-CoA, generating NADH and FADH2 for ATP production.

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Step 1 of beta-oxidation

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Acyl-CoA dehydrogenase removes 2H from the Cα-Cβ bond, forming trans-enoyl-CoA and producing FADH2. MCAD deficiency is the most common fatty acid oxidation disorder.

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MCAD deficiency findings

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MCAD: Most common fatty acid oxidation defect. Presents with hypoketotic hypoglycemia, vomiting, and lethargy during fasting. Elevated octanoylcarnitine on newborn screen.

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Locked

How many ATP from palmitate?

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Odd-chain fatty acid end product

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Frequently Asked Questions

Where does beta-oxidation occur?

Beta-oxidation occurs in the mitochondrial matrix. Long-chain fatty acids require the carnitine shuttle (CPT I and CPT II) to cross the inner mitochondrial membrane; short- and medium-chain fatty acids enter directly.

What is the difference between beta-oxidation and fatty acid synthesis?

Beta-oxidation occurs in the mitochondria, uses FAD/NAD+, and degrades fatty acids to acetyl-CoA.

Fatty acid synthesis occurs in the cytoplasm, uses NADPH, and builds fatty acids from acetyl-CoA via malonyl-CoA intermediates.

  • Location: mitochondria vs. cytoplasm
  • Cofactors: FAD/NAD+ vs. NADPH

How does fasting affect beta-oxidation?

During fasting, low insulin and high glucagon activate hormone-sensitive lipase, releasing fatty acids from adipose tissue. These are transported to the liver where beta-oxidation produces acetyl-CoA for ketogenesis and the TCA cycle.