BIOB32H3 Lecture : cells living unit.docx
28 Mar 2013
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Document Summary
Plasma membrane: separates intracellular fluids from extracellular fluids, plays a dynamic role in cellular activity, glycocalyx is a glycoprotein area abutting the cell that provides highly specific biological markers by which cells recognize one another. Fluid mosaic model: double bilayer of lipids with imbedded, dispersed proteins, bilayer consists of phospholipids, cholesterol, and glycolipids, glycolipids are lipids with bound carbohydrate, phospholipids have hydrophobic and hydrophilic bipoles. Functions of membrane proteins: transport, enzymatic activity, receptors for signal transduction, intercellular adhesion, cell-cell recognition, attachment to cytoskeleton and extracellular matrix. Membrane junctions: tight junction impermeable junction that encircles the cell, desmosome anchoring junction scattered along the sides of cells, gap junction a nexus that allows chemical substances to pass between cells. Passive membrane transport: diffusion: simple diffusion nonpolar and lipid-soluble substances, diffuse directly through the lipid bilayer, diffuse through channel proteins, facilitated diffusion large, polar molecules such as simple sugars, combine with protein carriers.
