Products generated in each β-oxidation cycle During mitochondrial β-oxidation of a saturated even-chain fatty acyl-CoA, what are the stoichiometric products formed in one complete cycle?

Introduction / Context:β-oxidation shortens fatty acyl chains by two carbons per cycle and provides reducing equivalents for ATP production. Knowing the per-cycle output is key for calculating total ATP yield from a given fatty acid.

Given Data / Assumptions:

• Saturated, even-chain acyl-CoA as substrate.
• Enzymes act sequentially: acyl-CoA dehydrogenase, enoyl-CoA hydratase, hydroxyacyl-CoA dehydrogenase, thiolase.
• Oxidative steps generate FADH2 and NADH; thiolysis liberates acetyl-CoA.

Concept / Approach:Each cycle comprises two oxidations and one thiolytic cleavage. The two-carbon unit leaves as acetyl-CoA; the chain is shortened to re-enter the next cycle until fully degraded.

Step-by-Step Solution:Dehydrogenation: acyl-CoA → trans-enoyl-CoA + FADH2.Hydration: trans-enoyl-CoA + H2O → L-3-hydroxyacyl-CoA.Dehydrogenation: L-3-hydroxyacyl-CoA → 3-ketoacyl-CoA + NADH.Thiolysis: 3-ketoacyl-CoA + CoA → acetyl-CoA + shortened acyl-CoA.

Verification / Alternative check:Textbook ATP yield calculations for palmitate incorporate per-cycle production of 1 FADH2, 1 NADH, and 1 acetyl-CoA (with a final extra acetyl-CoA on the last cleavage).

Why Other Options Are Wrong:Options with CO2 are incorrect; CO2 is produced in the citric acid cycle, not β-oxidation.Listing NAD+ or FAD as products is incorrect; they are oxidized cofactors consumed, not produced.Propionyl-CoA arises from odd-chain oxidation, not even-chain substrates.

Common Pitfalls:Mixing β-oxidation outputs with TCA outputs; forgetting that the final round yields an additional acetyl-CoA without another FADH2/NADH set.

Final Answer:1 FADH2, 1 NADH and 1 acetyl-CoA.