Answer: Its intermediates (pyruvate, acetyl CoA, oxaloacetate, etc.) serve as starting points for biosynthesis of fatty acids and amino acids, not just energy release.
- A It mainly channels every carbon atom from glucose toward ATP generation, with little diversion permitted regardless of the cell's current biosynthetic demand for amino acid or lipid precursors
- B Its intermediates (pyruvate, acetyl CoA, oxaloacetate, etc.) serve as starting points for biosynthesis of fatty acids and amino acids, not just energy release
- C It is physically split between the cytoplasm for glycolysis and the mitochondrial matrix for the Krebs cycle, a spatial separation that defines compartmentalization rather than its amphibolic character
- D It can be run largely in reverse to regenerate glucose directly from carbon dioxide using the same enzymes and without any net energy input required to drive the reaction
Correct answer: B. Its intermediates (pyruvate, acetyl CoA, oxaloacetate, etc.) serve as starting points for biosynthesis of fatty acids and amino acids, not just energy release
Explanation: Amphibolic = both catabolic and anabolic. Glycolysis/Krebs cycle intermediates are diverted into biosynthetic pathways for fatty acids, amino acids, and other biomolecules, not solely used for ATP production.
Aerobic respiration unfolds in three locations: glycolysis in the cytoplasm yields a small amount of ATP directly, the Krebs cycle in the mitochondrial matrix harvests electron carriers (NADH, FADH2), and the electron transport chain in the inner mitochondrial membrane uses those carriers to generate the bulk of the ATP, with O2 needed only at this final stage.
Concept context
Glycolysis, the Krebs cycle, the electron transport chain, fermentation, and the respiratory quotient. The cellular energy-release counterpart to photosynthesis.