Which description correctly defines beta-oxidation?

• A. A metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA. - occurs in the mitochondria
• B. The conversion of fat to glycogen
• C. Synthesis of fatty acids
• D. The process of breaking down proteins into amino acids

Answer: (A)

Beta-oxidation is the process by which fatty acids are broken down in a repeating cycle to remove two-carbon units as acetyl-CoA, with each cycle also producing NADH and FADH2 to fuel energy production. The acetyl-CoA generated then feeds into the citric acid cycle to generate more energy. This pathway primarily happens in mitochondria, which is why the description that it breaks fatty acids into two-carbon fragments that enter the citric acid cycle as acetyl-CoA and occurs in the mitochondria fits perfectly. The other descriptions refer to fat storage as glycogen, fatty acid synthesis, or protein breakdown, which are not beta-oxidation.