Membrane Transport

Also called

plasma membrane · fluid mosaic model · lipid bilayer · phospholipid · passive transport · simple diffusion · facilitated diffusion · channel protein · carrier protein · active transport · sodium potassium pump · Na+/K+ ATPase · endocytosis · exocytosis · selectively permeable membrane · कोशिका झिल्ली · सक्रिय परिवहन · विसरण

Topics

• The plasma membrane is a lipid bilayer: phosphate heads face the water on both sides, fatty tails hide inside.
• Proteins float in the bilayer like a mosaic; the membrane is fluid, so lipids and proteins can move sideways.
• Simple diffusion: small or non-polar molecules such as O₂ and CO₂ slip straight through the lipids, high to low.
• Facilitated diffusion uses channel or carrier proteins to move polar molecules and ions down their gradient.
• A carrier protein binds its passenger, changes shape and releases it on the other side, as with glucose.
• Active transport moves ions against their gradient using ATP: the Na⁺/K⁺ pump sends 3 Na⁺ out and 2 K⁺ in per ATP.
• Endocytosis takes material in by folding the membrane into a vesicle; exocytosis releases it by fusing one out.
• The membrane is selectively permeable: it decides what enters and leaves the cell.

About this model

A GLB file of about 538 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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