chap 4 membranes fall '08

chap 4 membranes fall '08 - CELL MEMBRANE CELL STRUCTURE...

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Unformatted text preview: CELL MEMBRANE CELL STRUCTURE AND FUNCTION STRUCTURE CHAPTER 4 TODAY WE WILL TODAY INVESTIGATE HOW CELL MEMBRANE INVESTIGATE STRUCTURE IS RELATED TO FUNCTION STRUCTURE DISCOVER HOW SUBSTANCES MOVE DISCOVER ACROSS MEMBRANES ACROSS LOOK AT HOW A CELL SURFACE IS LOOK SPECIALIZED SPECIALIZED Prokaryotic cell Eukaryotic cell The Cell’s Membranes The Are found – Surrounding a cell = plasma Surrounding membrane membrane – Surrounding organelles = membrane Surrounding organelles What do building or room walls do ? And what do walls provide? Membranes Membranes •Separate environments •Permit different environments STRUCTURE OF MEMBRANES STRUCTURE ALL MEMBRANES SIMILAR ALL HAVE 1.DOUBLE LAYER OF PHOSPHOLIPIDS 1.DOUBLE 2. IN WHICH “FLOAT” PROTEINS 3. AND CHOLESTEROL 3. A “”FLUID MOSAIC”” WHAT THE 3 PARTS DO WHAT –PHOSPHOLIPIDS Basic building block of membranes PHOSPHOLIPID GIVEN GIVEN Cells exist in a water medium Cells Inside the cell: the cytoplasm Inside Outside the cell: the extracellular fluid AND ALSO GIVEN AND A phospholipid molecule has – one end that likes likes water water – one end that repels repels water water NOTE KINK – and a polar head that forms hydrogen bonds forms likes repels Polar When SO, When in a water environment, phospholipid molecules spontaneously arrange themselves spontaneously so that their “hate” water tails are together so water forming a forming “phospholipid bilayer” = a membrane Wow!! ! 10,000 membranes = thickness of a sheet of paper Note: there are no bonds between phospholipids and their tails have kinks, therefore they can slide past onerepels another A fluid mosaic. likes Fluid = any substance that moves/changes shape w/o breaking apart Why phospholipids form a membrane Why Cells exist in a water medium Cells – Inside: a fluid based cytoplasm – Outside: the extracellular fluid Review slide A phospholipid molecule has – – – likes one end that likes water one one end that repels water one a polar head polar repels Polar head These molecules spontaneously form a “phospholipid bilayer” form Polar heads form hydrogen bonds Polar with water with Because of “kinks” in molecules Because and no bonds the bilayer is ‘fluid’ 10,000 membranes = thickness of a sheet of paper – PHOSPHOLIPIDS Building block Separates environments Permits different environments WHAT THE 3 PARTS DO WHAT – PROTEINS act as Gatekeepers = lets selected stuff pass to and fro Gatekeepers Communicators = chemically pass signals through membrane through Cell ID tags (glycoproteins) Cell Enzymes Enzymes Junction proteins Junction PROTEIN TYPES/FUNCTIONS IN MEMBRANE MEMBRANE Literally 000’s (each doing a specific task) embedded or attached to Literally each bilayer Many freely float in membrane Many Others attach to protein filaments, anchoring them, and giving cells their Others giving peculiar shape e.g. disc shaped red blood cells peculiar PROTEIN TYPES/FUNCTIONS IN MEMBRANE PROTEIN Literally 000’s (each doing a specific task) embedded or each attached to bilayer Many freely float in membrane Many Others attach to protein filaments, anchoring them, Others and giving cells their peculiar shape e.g. disc shaped red blood cells red 3 major categories major 1. Transport proteins 2 types – – 2. 3. move items in/out of cell Channel Carrier Receptor proteins when triggered, cause an action Recognition proteins cell id tags PROTEIN TYPES/FUNCTIONS IN MEMBRANE PROTEIN Literally 000’s (each doing a specific task) embedded or each attached to bilayer Many freely float in membrane Many Others attach to protein filaments, anchoring them, Others and giving cells their peculiar shape e.g. disc shaped red blood cells red 3 major categories major 1. Transport proteins move items in/out of cell 2 types – Channel: Channel: – Carrier: Carrier: 2. Receptor proteins 2. – 3. 3. when triggered, cause an action Trigger specific response when molecules in extracellular fluid Trigger attach to them (chemical signal) Recognition proteins cell id tags PROTEIN TYPES/FUNCTIONS IN MEMBRANE PROTEIN Literally 000’s (each doing a specific task) embedded or Literally each attached to bilayer Many freely float in membrane Many Others attach to protein filaments, anchoring them, Others and giving cells their peculiar shape e.g. disc shaped red blood cells red 3 major categories major 1. 2. 2. Transport proteins move items in/out of cell 2 types – Channel: Channel: – Carrier: Carrier: Receptor proteins when triggered, cause an action – Trigger specific response when molecules attach to them 3. Recognition proteins cell id tags Glycoproteins = protein + attached carbohydrate Glycoproteins Enzymes Junction proteins WHAT THE 3 PARTS DO WHAT – – PHOSPHOLIPIDS Separates environments Permits different environments PROTEINS act as Gatekeepers = lets selected stuff pass to and fro Gatekeepers Communicators = chemically pass signals through membrane Communicators Cell ID tags (glycoproteins) Cell –CHOLESTEROL Stronger membrane More flexible but less fluid Plasma membranes are selectively permeable are selectively Some substances can Some can freely move across the membrane some cannot freely move cannot Definitions Fluid Fluid Concentration Gradient Concentration gradient Diffusion Dynamic equilibrium Selectively permeable Definitions Definitions Fluid = any substance that moves/changes shape w/o breaking Fluid apart e.g. liquids & gases apart Gradient = the difference in a property between two adjoining Gradient regions regions Property = Temp, pressure, [ ], charge – – Concentration [ ] = number of molecules in a fluid in a given unit Concentration of volume of Concentration gradient = a difference in concentrations between Concentration adjacent regions adjacent Diffusion = movement of molecules from high [ ] to low [ ] Diffusion Note: liquid level stays same; it’s the molecules that move from one region to Note: another another Eventually produces a condition called dynamic equilibrium, a condition which Eventually dynamic equilibrium, condition eliminates the ‘concentration gradient’. Note: although the molecules are still in motion, there is no longer any Note: change in [ ] levels change Plasma membranes are selectively permeable selectively Some substances can freely move across the membrane some cannot freely move freely NO ENERGY REQUIRED PASSIVE TRANSPORT moves a substance from a higher [ ] to a lower [ ] ENERGY REQUIRED ENERGY TRANSPORT Passive transport (no energy required) 2 types Simple diffusion Facilitated diffusion Osmosis: a special form of diffusion Osmosis: Still no energy required Diffusion of water across a selectively permeable membrane--- that is, a membrane that is more Diffusion permeable to water than other given molecules permeable 1 Note that the sugar molecules stay in the permeable bag; because they are too big to pass through the pores the membrane. ENERGY TRANSPORT ENERGY ACTIVE TRANSPORT EXOCYTOSIS ENDOCYTOSIS ENERGY TRANSPORT ENERGY movement of substances into or out of the cell with cellular energy Active transport Active moves ions against [ ] gradient i.e. low [ ] to moves high [ ] high Endocytosis 3 types Pinocytosis = cell drinking Receptor­mediated = selective eating Phagocytosis = cell eating Exocytosis Exocytosis ejection of particles from cells ejection How Cells Attach, Communicate, Support How Cells attach to one another by protein strands – Desmosomes intestines intestines & Tight junctions urinary bladder Cells communicate by Cells Gap junctions Gap protein channels (animals) protein & Plasmodesmata openings in plant cell walls Cell Support Cell Cell walls Cell – plants and some bacteria and fungi have cells w/walls cells – Made of cellulose or Made protein or silica or combo combo What did we cover today? What Membranes – – – – – Plasma or internal Made of phospholipids, proteins, cholesterol Bilayer, repel, attract, kink Transport (2), receptor, recognition proteins Cholesterol: less fluid more flexible membranes Fluids, diffusion, gradients, [ ] gradients Passive vs. energy transport – Diffusion, facilitated diffusion, osmosis – Active, endocytosis (3), exocytosis Attch (2), communicate (2), support Reminder to start the study process process amen amen ...
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This note was uploaded on 06/02/2011 for the course BIOL 110 taught by Professor Duwel during the Fall '08 term at South Carolina.

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