Tortora - Chapter 3 - The Cellular Level of Organization.ppt

Tortora - Chapter 3 - The Cellular Level of...

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Unformatted text preview: 3-1Chapter 3The Cellular Level of OrganizationBasic, living, structural and functional unit of the bodycompartmentalization of chemical reactions within specialized structuresregulate inflow & outflow of materialsuse genetic material to direct cell activitiesCytology = study of cellular structureCell physiology = study of cellular function3-2Generalized Cell StructuresPlasma membrane = cell membraneNucleus = genetic material of cellCytoplasm = everything between the membrane and the nucleuscytosol = intracellular fluidorganelles = subcellular structures with specific functions3-3The Typical CellNot all cells contain all of these organelles.3-43-5Plasma MembraneFlexible but sturdy barrier that surround cytoplasm of cellFluid mosaic model describes its structuresea of lipids in which proteins float like icebergsmembrane is 50 % lipid & 50 % protein held together by hydrogen bondslipid is barrier to entry or exit of polar substancesproteins are gatekeepers -- regulate traffic50 lipid molecules for each protein molecule3-6Lipid Bilayer of the Cell MembraneTwo back-to-back layers of 3 types of lipid moleculesCholesterol and glycolipids scattered among a double row of phospholipid molecules3-7PhospholipidsComprises 75% of lipidsPhospholipid bilayer = 2 parallel layers of moleculesEach molecule is amphipathic (has both a polar & nonpolar region)polar parts (heads) are hydophilic and face on both surfaces a watery environment nonpolar parts (tails) are hydrophobic and line up next to each other in the interior3-8Glycolipids within the Cell MembraneComprises 5% of the lipids of the cell membraneCarbohydrate groups form a polar head only on the side of the membrane facing the extracellular fluid3-9Cholesterol within the Cell MembraneComprises 20% of cell membrane lipids Interspersed among the other lipids in both layersStiff steroid rings & hydrocarbon tail are nonpolar and hide in the middle of the cell membrane3-10Types of Membrane ProteinsIntegral proteinsextend into or completely across cell membraneif extend completely across = transmembrane proteinsall are amphipathic with hydrophobic portions hiding among the phospholipid tailsglycoproteins have the sugar portion facing the extracellular fluid to form a glycocalyxgives cell uniqueness, protects it from being digested, creates a stickiness to hold it to other cells or so it can hold a fluid layer creating a slippery surfacePeripheral proteinsattached to either inner or outer surface of cell membrane and are easily removed from it3-11Membrane ProteinsIntegral versus Peripheral Proteins3-12Functions of Membrane ProteinsFormation of Channelpassageway to allow specific substance to pass throughTransporter Proteinsbind a specific substance, change their shape & move it across membraneReceptor Proteinscellular recognition site -- bind to substance 3-13...
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This note was uploaded on 06/11/2009 for the course BIOL 251 taught by Professor Hurrell during the Spring '09 term at Delgado CC.

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Tortora - Chapter 3 - The Cellular Level of...

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