Passive transport of ions and polar molecules down a gradient through channel or carrier proteins.
Channel proteins form water-filled pores that open or close (gated by voltage or ligands), while carrier proteins change shape as they bind and release a solute. Both are specific and can become saturated, unlike simple diffusion.
The direction is always down the gradient and needs no ATP. Aquaporins allow rapid water movement and GLUT transporters bring glucose into cells.
Passive transport of ions and polar molecules down a gradient through channel or carrier proteins.
Facilitated Diffusion is one of the 52 topics in Cell Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Active Transport, Simple Diffusion, Nuclear Pore Complex.
Red blood cells take up glucose through GLUT1 carriers.
Work through the Beginner topics in Cell Biology first, such as Cell Theory, Prokaryotic Cell, Eukaryotic Cell, then return to Facilitated Diffusion. Intermediate topics assume the Beginner vocabulary.
The closest topics to Facilitated Diffusion are Active Transport, Simple Diffusion, Nuclear Pore Complex, Osmosis. Comparing them side by side is a good way to see how the ideas connect.
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Facilitated Diffusion. To practise the whole of Cell Biology, use the Cell Biology quiz.
Facilitated Diffusion: Passive transport of ions and polar molecules down a gradient through channel or carrier proteins. Active Transport: Movement of substances against their gradient using energy, usually ATP, via carrier proteins called pumps. Read both side by side and note what each one explains.
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Active Transport and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.
Movement of substances against their gradient using energy, usually ATP, via carrier proteins called pumps.
🔬 Cell BiologyPassive movement of small nonpolar molecules down their concentration gradient directly across the membrane.
🔬 Cell BiologyA large protein assembly that gates the nuclear envelope, controlling traffic of RNA and proteins via importins.
🔬 Cell BiologyThe diffusion of water across a selectively permeable membrane from lower to higher solute concentration.
🔬 Cell Biology