--- title: "Control Points in Glycolysis and the Committed Step" description: "Several far-from-equilibrium glycolytic reactions are common regulatory sites. PFK-1 responds to ATP, AMP and citrate and catalyses the committed step. Control of pathway flux can be distributed acros" canonical: https://lightmysky.com/learn/science/control-points-in-glycolysis-and-the-committed-step-mt_2vAoKtnmoz source: https://lightmysky.com/learn/science/control-points-in-glycolysis-and-the-committed-step-mt_2vAoKtnmoz.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Control Points in Glycolysis and the Committed Step Several far-from-equilibrium glycolytic reactions are common regulatory sites. PFK-1 responds to ATP, AMP and citrate and catalyses the committed step. Control of pathway flux can be distributed across enzymes and depends on cellular conditions. Subject: Science · Area: Biochemistry & Molecular Biology · Ages 19 to 21 Page: https://lightmysky.com/learn/science/control-points-in-glycolysis-and-the-committed-step-mt_2vAoKtnmoz ## Ready when they can - Names the three common far-from-equilibrium glycolytic reactions and explains why PFK-1 catalyses the committed step. - Predicts PFK-1 responses to inhibitory ATP, AMP and citrate under stated conditions. - Uses stated perturbation results to compare flux control without inferring it from equilibrium status alone. ## Lesson: How glycolysis responds to regulation Mammalian glycolysis has three common far-from-equilibrium reactions: glucose phosphorylation by hexokinase or glucokinase; fructose-6-phosphate phosphorylation by PFK-1; and conversion of phosphoenolpyruvate to pyruvate by pyruvate kinase. Strongly negative delta G under cell conditions makes direct reversal negligible. Many remaining reactions are closer to equilibrium and can reverse as concentrations change. PFK-1 is phosphofructokinase-1. It converts fructose-6-phosphate to fructose-1,6-bisphosphate using ATP. This is the committed glycolytic step because earlier glucose-6-phosphate can enter other pathways, such as glycogen production or the pentose phosphate pathway. Commitment concerns pathway entry after those branches, not exclusive ownership of flux control. *(drawing: PFK-1 catalyses the committed glycolytic reaction after earlier branch points.)* ATP is a PFK-1 substrate, but at high concentrations it can also inhibit the enzyme allosterically. AMP can activate PFK-1 as energy demand rises. Citrate can inhibit it too. Citrate abundance may reflect metabolic supply and demand, but does not uniquely prove that a downstream pathway is full. Predict direct enzyme effects with other conditions stated. Flux control can be shared among enzymes and depends on conditions. Near-equilibrium status alone does not predict the effect of inhibition. To compare targets, apply the same activity reduction to each under the same conditions and measure steady-state pathway flux. A larger measured flux decrease indicates a stronger effect for that tested perturbation, not a universal best target. *(drawing: An enzyme response is one part of pathway control; whole-pathway flux also depends on other conditions.)* **Recap.** PFK-1 catalyses glycolysis's committed step and responds to energy-related signals. Common regulatory reactions do not alone determine all pathway flux control. *Lesson, questions and flashcards written for this dataset.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Coupled Reactions and Why ATP Is the Cell's Currency](https://lightmysky.com/learn/science/coupled-reactions-and-why-atp-is-the-cells-currency-mt_1yVJRArCow) ## Optional connections - [Glycolysis and the Link Reaction](https://lightmysky.com/learn/science/glycolysis-and-the-link-reaction-mt_crbadbBvqB) ## Opens up - [Gluconeogenesis and the Reciprocal Regulation of Opposing Pathways](https://lightmysky.com/learn/science/gluconeogenesis-and-the-reciprocal-regulation-of-opposing-pathways-mt_D1MbKcb6Le) - [Flux Control and Following Atoms with Labelled Substrates](https://lightmysky.com/learn/science/flux-control-and-following-atoms-with-labelled-substrates-mt_PzhsDwD_aW)