LIFESCI 2 Chapter Notes - Chapter 5 & 9: Extracellular Fluid, Tight Junction, Gap Junction
9 Apr 2017
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Document Summary
Many cells packed together, so membranes physically connected. 3 types: desmosomes, tight junctions, gap junctions. Found in cells of organs that are pulled & stretched so that they work together tight junction. Push cells close together to minimize the space between them. Prevents paracellular transport (so substance move inside cells/transcellular pathway) So that the cells can control the substance movement. Facilitate exchange of material between neighboring cells. Half protein in one cell, half in another. Small molecules & ions can pass thru. Occur thru lipid or protein (channels embedded in membrane that are specific for ions) no energy required stops when reaches equilibrium. O2, co2, any lipid soluble molecules, water can move thru lipid bilayer (water can also move thru protein channels called aquaporin) Polar & charged substances don"t move thru lipid portion: osmosis: diffusion of water across membranes. From low solute concentration to high solute concentration. Type of solution determines direction of water movement.
