Question1 Which statement about beta-oxidation of fatty acids is CORRECT? Select one alternative: Beta-oxidation occurs in the cytosol of cells The rate-limiting step of beta-oxidation is the entry of fatty acids into the mitochondrial matrix attached to albumin The ‘beta’ in beta-oxidation refers to the position of the carbon where cleavage occurs to generate acetyl CoA Beta-oxidation and fatty acid synthesis usually occur at the same time in a liver or fat cell Biochemically, beta-oxidation is the reverse of fatty acid synthesis ResetMaximum marks: 1 Flag question undefined

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Question1 Which statement about beta-oxidation of fatty acids is CORRECT? Select one alternative:
1) Beta-oxidation occurs in the cytosol of cells
2) The rate-limiting step of beta-oxidation is the entry of fatty acids into the mitochondrial matrix attached to albumin
3) The ‘beta’ in beta-oxidation refers to the position of the carbon where cleavage occurs to generate acetyl CoA
4) Beta-oxidation and fatty acid synthesis usually occur at the same time in a liver or fat cell
5) Biochemically, beta-oxidation is the reverse of fatty acid synthesis

Option 1: Beta-oxidation occurs in the cytosol of cells. This statement is inaccurate because beta-oxidation primarily takes place inside the mitochondria (and, for very long-chain fatty acids, can also occur in peroxisomes). The cytosolic environment is where fatty acid activation and transport into mitochondria occur, but the actual degradation steps are mitochondrial. Misplacing the site of the process would imply the energy and shuttle requirements are different from what is observed in physiology.

Option 2: The rate-limiting step of beta-oxidation is the entry of fatty acids into the mitochondrial matrix attached to albumin. This is incorrect for a couple of reasons. First, fatty acids are not transported into the matrix as free fatty acids bound to albumin; albumin brings them to the membrane, but entry involves the carnitine shuttle (CPT1/CPT2) after activation to acyl-CoA. Albumin binding is a transport in the blood, not a rate-limiting intracellular step. The rate-limiting control point is often the regulation of CPT1 by malonyl-CoA, not merely the physical entry step itself.

Option 3: The ‘beta’ in beta-oxidation refers to the position of the carbon where cleavage occurs to generate acetyl CoA. This statement captures the core nomenclature: beta-oxidation cleaves 2-carbon units at the beta (3rd) carbon relative to the carbonyl carbon of the fatty acyl chain, yielding acetyl-CoA units. The beta position designation reflects the specific carbon atom involved in the oxidation-cleavage chemistry, making this a correct conceptual description.

Option 4: Beta-oxidation and fatty acid synthesis usually occur at the same time in a liver or fat cell. In reality, these pathways are tightly regulated and generally occur in opposite directions in the same cell under many conditions. Fatty acid synthesis (lipogenesis) builds fatty acids, while beta-oxidation breaks them down; simultaneous upregulation is context-dependent and not typically described as “usually occur at the same time.” This statement is thus misleading.

Option 5: Biochemically, beta-oxidation is the reverse of fatty acid synthesis. While there are conceptual parallels between the two pathways, they are not exact reverses. The enzymes, cofactors, compartmentalization, and regulatory controls differ between degradation and synthesis. Treating them as exact reverses is an oversimplification and is not accurate.

In summary, option 3 aligns with the established definition of beta-oxidation’s naming and mechanism, while the other statements conflict with fundamental aspects of cellular location, transport, regulation, and pathway relationship.

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