Membrane Transport Proteins

Run the membrane

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Transport experiment

80
25
−70 mV
100%

Live measurements

Net transport rate0.00 /s
Outside → insideinward
Protein stateopen

sodiumglucosewater

Camera & focus

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Focus: none. Tap a molecule, membrane, or protein.

Teacher demo tools

Transport history

Interactive teacher lecture

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What to watch

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Teacher transcript

The matching membrane action, protein motion, and directional arrows will appear on the canvas while each step is spoken.

Lesson chapters

Learning objectives

  • Distinguish simple passage, channels, carriers, pumps, and cotransport.
  • Predict net movement from concentration and electrical gradients.
  • Explain why carriers saturate but open pores can pass many particles.
  • Connect ATP hydrolysis to movement against a gradient.
  • Relate protein shape changes to selective transport.

What the model demonstrates

The phospholipid core resists ions and most polar solutes. Selective membrane proteins provide a hydrophilic route or bind a specific solute. Passive transport follows the electrochemical gradient; active transport uses stored energy to oppose it.

Particle size and speed are conceptually scaled. Concentrations and rates are educational units, not direct laboratory measurements.

Suggested experiments

  1. Open an ion channel, reverse the concentration gradient, and watch the arrow reverse.
  2. Close the gate and compare the rate with the same gradient.
  3. Raise glucose concentration in carrier mode until rate increases very little.
  4. Set ATP to zero in pump mode, then restore it.
  5. Compare aquaporin and symporter movement.

Real-world connections

Ion channels create nerve signals. Aquaporins regulate water balance. Glucose carriers feed cells. The sodium–potassium pump maintains gradients used by neurons, muscles, and secondary active transport.

Common misconceptions

  • Equilibrium is dynamic; molecules still move both ways.
  • A channel does not push particles by itself.
  • Active transport is not simply “fast transport”; it is transport coupled to energy.
  • Membrane proteins are selective, not universal holes.

Visual concept quiz

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