Can you identify the products in fatty acid beta-oxidation? In this free interactive biochemistry quiz, trace one complete four-step round of mitochondrial beta-oxidation, starting with palmitoyl-CoA (C16:0). Each choice pairs a chemical structure with a compound name.
Interactive Fatty Acid Beta-Oxidation Quiz: All 4 Steps
Follow the same continuous three-choice → reaction arrow → three-choice format as our TCA Cycle Quiz. Each question has exactly one correct choice. The last reaction produces two products: acetyl-CoA and a fatty acyl-CoA shortened by two carbons.
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Four Reactions of Fatty Acid Beta-Oxidation
| Step | Reaction | Enzyme activity | Key outcome |
|---|---|---|---|
| 1 | Dehydrogenation | Acyl-CoA dehydrogenase (VLCAD for this long-chain example) | trans-Δ²-enoyl-CoA; electrons transferred to FAD-dependent pathway |
| 2 | Hydration | Enoyl-CoA hydratase | L-3-hydroxyacyl-CoA |
| 3 | Dehydrogenation | 3-Hydroxyacyl-CoA dehydrogenase | 3-ketoacyl-CoA; NADH produced |
| 4 | Thiolysis | 3-Ketoacyl-CoA thiolase | Acetyl-CoA + two-carbon-shorter acyl-CoA |
Why Does Beta-Oxidation Repeat?
Each complete spiral shortens the fatty acyl chain by two carbons. Starting from a 16-carbon saturated palmitoyl-CoA, the first round gives myristoyl-CoA (C14:0) and acetyl-CoA. After seven rounds, one palmitoyl-CoA produces eight acetyl-CoA, seven NADH and seven FADH₂ equivalents. Activation of palmitate to palmitoyl-CoA and the carnitine shuttle are important preparatory processes but are not counted as the four recurring reactions.
How to Read the Chemical Structures
Watch the carbon atoms adjacent to the thioester carbonyl: the α-carbon is C2 and the β-carbon is C3. A trans double bond appears between C2 and C3; hydration adds the hydroxyl group at C3; oxidation makes a C3 ketone; thiolysis splits off a two-carbon acetyl group. Coenzyme A structures are large, so compare the fatty acyl chain near the thioester bond when choosing an answer.
Frequently Asked Questions
How many steps are in beta-oxidation?
The repeating mitochondrial beta-oxidation spiral has four reactions: dehydrogenation, hydration, a second dehydrogenation and thiolysis.
What is produced in one round of beta-oxidation?
One acetyl-CoA, a fatty acyl-CoA shortened by two carbons, one NADH and one FADH₂ equivalent (via the FAD-dependent acyl-CoA dehydrogenase electron-transfer pathway).
How many cycles does palmitoyl-CoA need?
Seven rounds yield eight acetyl-CoA molecules from a 16-carbon saturated acyl-CoA.
Does beta-oxidation happen in the mitochondrial matrix?
Mitochondrial beta-oxidation takes place at the matrix side of the inner mitochondrial membrane and in the matrix; the long-chain mitochondrial trifunctional protein is associated with the inner membrane.
Explore Related Biochemistry Quizzes
See where acetyl-CoA goes next in the TCA Cycle Quiz, or review Glycolysis, the Pentose Phosphate Pathway, and the Urea Cycle.
References
NCBI Bookshelf — Biochemistry, Fatty Acid Oxidation. Reactome/PubChem — Beta oxidation of palmitoyl-CoA to myristoyl-CoA.