PSYC 2000 Chapter : Memory 28 29
Document Summary
Individual molecules move randomly, but the net effect is non-random: energy changes, molecules move from high concentration to low concentration/ high energy to low energy. (spontaneous process), releases energy as it crosses the barrier. Osmosis-net movement of water across (through) a semi-permeable (permeable to water but not to one or more solutes all biological membranes are semi-permeable) membrane. Permeases: membrane bound proteins that facilitate the movement of molecules across the membrane, categorized by energy use, passive, use no energy, active, use energy. Passive: facilitate diffusion, moves molecules down their free energy (concentration gradient) Facilitate diffusion carrier types: protein carrier: proteins carry the molecules across, protein channel: proteins have large holes in them that the molecule can then cross, facilitate diffusion carriers are very selective. Active: active transport, moves molecules against their free energy (concentration gradient, protein carrier, selective and requires energy (usually atp) Other kinds of moment into a cell: vesicle-mediated transport, endocytosis, exocytosis, not movement through a membrane.
