---
title: "Co-transport and Coupled Movement Across Membranes"
description: "An ATP-driven pump maintains an ion gradient. A second carrier uses movement down that gradient to move another substance against its gradient. Sodium-dependent glucose entry into gut lining cells is "
canonical: https://lightmysky.com/learn/science/co-transport-and-coupled-movement-across-membranes-mt_pzQ8n3FWNV
source: https://lightmysky.com/learn/science/co-transport-and-coupled-movement-across-membranes-mt_pzQ8n3FWNV.md
retrieved: 2026-11-12
---

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# Co-transport and Coupled Movement Across Membranes

An ATP-driven pump maintains an ion gradient. A second carrier uses movement down that gradient to move another substance against its gradient. Sodium-dependent glucose entry into gut lining cells is the example.

Subject: Science · Area: Organisms & Life Processes · Ages 17 to 18
Page: https://lightmysky.com/learn/science/co-transport-and-coupled-movement-across-membranes-mt_pzQ8n3FWNV

## Ready when they can

- Separates the step that spends ATP from the step that rides the gradient.
- Traces sodium export by the pump and coupled sodium and glucose entry through the symporter.
- Explains why blocking the pump reduces sodium-dependent glucose uptake as the sodium gradient weakens, although the symporter uses no ATP directly.

## Lesson: How gut cells pull in glucose

You have met ATP-driven pumps. In a gut lining cell, the sodium potassium pump faces tissue fluid, not the gut lumen, the space holding food. It uses ATP to export sodium and import potassium, keeping sodium low inside. This direct ATP use is primary active transport. Ions respond to concentration and voltage differences together: an electrochemical gradient.

On the lumen-facing membrane, the sodium glucose symporter couples sodium entry down its electrochemical gradient to glucose entry, even against glucose's concentration gradient. Both substances enter together: this is symport. The symporter uses the gradient without splitting ATP. It is secondary active transport because its energy comes indirectly from the ATP-driven pump.

*(drawing: This is an energy dependency. In a working cell, pumping and coupled uptake continue together.)*

**Example.** If a cell starts without a sodium gradient, the pump must establish one before it can support uptake. Blocking the pump later does not erase that gradient at once. The symporter may still use it briefly. As sodium enters without being pumped out, the gradient weakens and sodium-dependent glucose entry decreases. A gradient that supplies too little energy cannot sustain glucose entry against its concentration gradient.

A symporter couples movement of substances in the same direction across a membrane. An antiporter couples movement in opposite directions: one substance enters while another leaves. These names describe transport directions. They do not, by themselves, tell you whether a carrier uses ATP directly.

**Recap.** ATP powers the pump. Its sodium gradient drives coupled sodium and glucose entry through the symporter. Uptake decreases as that driving gradient weakens.

*Lesson, questions and flashcards written for this dataset.*

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Active Transport Against the Gradient](https://lightmysky.com/learn/science/active-transport-against-the-gradient-mt_BQf1bgo9oM)

## Opens up

- [The Resting Potential and the Action Potential](https://lightmysky.com/learn/science/the-resting-potential-and-the-action-potential-mt_0sh4w30ocz)
- [Ion Channels: Selectivity, Gating and the Evidence from Single Channels](https://lightmysky.com/learn/science/ion-channels-selectivity-gating-and-the-evidence-from-single-channels-mt_2xPzPeXZZ_)
- [Equilibrium potentials and what sets the resting voltage](https://lightmysky.com/learn/science/equilibrium-potentials-and-what-sets-the-resting-voltage-mt_mRT_5vDEO1)
- [Ultrafiltration and Selective Reabsorption in the Nephron](https://lightmysky.com/learn/science/ultrafiltration-and-selective-reabsorption-in-the-nephron-mt_vSKfoJN6zh)
- [Translocation and the Mass Flow Hypothesis](https://lightmysky.com/learn/science/translocation-and-the-mass-flow-hypothesis-mt_WZ8id0kou4)