hard · MCAT bio-biochem
Phosphofructokinase-1 (PFK-1) activity was measured in isolated hepatocyte extracts under three conditions: (1) low ATP/high AMP, (2) high citrate, and (3) high fructose-2,6-bisphosphate (F2,6BP) added exogenously.
Which pairing correctly matches each condition with its effect on PFK-1 activity and the allosteric mechanism responsible?
- (1) activates by relieving ATP inhibition; (2) inhibits by increasing ATP's affinity for its inhibitory site; (3) activates by lowering the K_m for fructose-6-phosphate.
- (1) activates by relieving ATP inhibition; (2) inhibits by mimicking a low-energy signal at the substrate site; (3) inhibits by competing with fructose-6-phosphate at the active site.
- (1) inhibits by competing with AMP's stimulatory site; (2) activates by raising acetyl-CoA supply; (3) activates by lowering the K_m for fructose-6-phosphate.
- (1) activates by relieving ATP inhibition; (2) inhibits independent of ATP levels by acting at a distinct allosteric site; (3) inhibits by increasing sensitivity to citrate.
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