Glycolytic control — A catabolic intermediate that stimulates phosphofructokinase-1 (PFK-1) would be expected to stimulate which pathway overall?

Introduction:
Phosphofructokinase-1 (PFK-1) catalyzes the committed step of glycolysis: conversion of fructose-6-phosphate to fructose-1,6-bisphosphate using ATP. This question examines pathway logic: if a metabolite stimulates PFK-1, which overall pathway is driven forward?

Given Data / Assumptions:

• PFK-1 is a major regulatory node responding to energy status.
• Allosteric regulators include ATP (inhibitor), AMP/ADP (activators), and fructose-2,6-bisphosphate (potent activator).
• Directionality of metabolic flux follows the control of rate-limiting steps.

Concept / Approach:
Activation of PFK-1 accelerates glycolytic flux, increasing conversion of hexose phosphates to triose phosphates, pyruvate, and ultimately ATP. In liver, fructose-2,6-bisphosphate powerfully stimulates PFK-1 while inhibiting the opposing gluconeogenic enzyme FBPase-1, ensuring reciprocal control and preventing futile cycling.

Step-by-Step Solution:

Verification / Alternative check:
Hormonal signaling (insulin) raises hepatic fructose-2,6-bisphosphate, experimentally observed to increase glycolytic rate and suppress gluconeogenesis, confirming the pathway choice.

Why Other Options Are Wrong:

• Gluconeogenesis: reciprocally inhibited by regulators that activate PFK-1.
• Glycogen synthesis: controlled by glycogen synthase and insulin signaling; not a direct consequence of PFK-1 activation.
• Pentose phosphate pathway only: PPP branching is governed at glucose-6-phosphate dehydrogenase, not via PFK-1.
• None: incorrect because PFK-1 activation has a clear effect.

Common Pitfalls:
Overlooking tissue-specific nuances; although regulation varies by tissue, PFK-1 activation universally drives glycolysis forward.

Final Answer:
Glycolysis.