Apentix/AP Biology/Unit 3: Cellular Energetics/Question
AP Biologyhardmcq1 pt

When cellular ATP is abundant, the pace of glycolysis slows because ATP...

A.competes with glucose for hexokinase's active site
B.binds an allosteric site on phosphofructokinase, reducing the enzyme's affinity for fructose-6-phosphate
C.permanently denatures glycolytic enzymes at normal cellular concentration
D.directly phosphorylates fructose-6-phosphate without needing an enzyme

Explanation

Core Concept

Phosphofructokinase catalyzes the committed step of glycolysis and serves as its main control point. Besides its active site, the enzyme carries a regulatory pocket occupied by ATP when energy is plentiful. Binding there changes the enzyme's shape so fructose-6-phosphate attaches less readily, throttling flux into the pathway. AMP relieves this inhibition, letting cells speed glycolysis precisely when energy runs low.

Correct Answer

Bbinds an allosteric site on phosphofructokinase, reducing the enzyme's affinity for fructose-6-phosphate

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