Bio Chapter 7 Notes
Bio Chapter 7 Notes BIOl 1020-003
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This 3 page Class Notes was uploaded by Crystal Boutwell on Friday September 25, 2015. The Class Notes belongs to BIOl 1020-003 at Auburn University taught by Dr. Zhong in Fall 2015. Since its upload, it has received 31 views. For similar materials see Principles of Biology in Biology at Auburn University.
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Date Created: 09/25/15
CELL MEMBRANE Chapter 7 Compiled by Crystal Boutwell I Roles of Plasma Membrane A Selective membrane allows some substances to cross it more easily than others a Nonpolar and small polar molecules can cross without assistance although polar molecules will pass through slower due to the hydrophobic qualities of the fatty acid tails b Lipids can move relatively easily in the membrane B Functions a Isolates the cell s contents from the environment b Regulates exchange of essential substances c Communicates with other cells d Creates attachments with other cells e Provides a surface for biochemical reactions Fluid Mosaic Model A Definition membrane is a mosaic of protein molecules bubbling in a fluid bilayer of phospholipids Pacement is not random B Phospholipid bilayer the hydrophilic phosphate heads and hydrophobic fatty acid tails C Membrane remains fluid to a lower temperature if it contians lipids with unsaturated hydrocarbons Double bonds in hydrocarbons are unsaturated fatty acids These tails are kinked and cannot pack D Homoviscous adaptation an increase in unsaturated fatty acids at lower growth temperatures and an increase in saturated fatty acids at higher temperatures i Viscous sticky less fluid E Cholesterol in animal membranes stabilizes membrane fluidity i Makes the bilayer stronger and flexible i Less fluid at higher temperatures i Less solid at lower temperatures I iv Less permeable to water soluble substance F Proteins are embedded in the phospholipid bilayer i Two major populations of membrane proteins 1 Integral Proteins a Penetrate the interior of the bilayer b Mostly transmembrane proteins span the membrane c Contain nonpolar amino acids coiled into alpha helices 2 Peripheral proteins a Appendages loosely bound to the membrane ii 6 major functions of Proteins Transport Enzymatic activity Signal transduction Cellcell recognition P PPP Intercellularjoining 6 Attachment to the cytoskeleton and ECM G Membrane carbohydrates cellcell recognition i Cells recognize other cells by binding to molecules containing carbohydrates on the extracellular surface of the plasma membrane ii Covalently bonded to lipids glycopids iii Bonded to proteins glycoproteins iv Blood types H Synthesis and sideness i Membrane build by ER and Golgi App ii Inside and outside faces iii Differ Transport and Transfer across the cell membrane A Transport proteins span the membrane and allow ions and polar molecules through the cell membrane i Channel proteins hydrophilic channel 1 Aquaporins water ii Carrier proteins shuttle service iii Selective to the object it transports B Diffusion spreading out into available space i Net movement of particles from an area of higher concentration to an area of lower concentration C Passive transport cell does not expend energy to diffuse Moves down its concentration gradient i Facilitated Diffusion 1 Small polar molecules can SLOWLY goa cross the membrane on their own Facilitated diffusion speeds up the process of diffusion through a channel protein 2 Large molecules D Osmosis diffusion of water water always moves from hypotonic to hypertonic i Osmosis in plant cells 1 Hypertonic solution a Plasmolyzed the insides ofthe cell shriveled Cell membrane pulls away as plant cell shrinks 2 Isotonic flaccid or limp not so great for plant cells 3 Hypotonic ideal for plant cells a increases pressure between cytoplasm and cell wall b Turgid pressure makes a cell wall sturdy and firm c Turgidity the pressure of the cell contents against the cell wall in plant and bacteria cells 4 Osmoregulation the control of solute concentrations and water balance ii Osmosis in animal cells 1 Isotonic is ideal for animal cells 2 Hypertonic cell will eventually shrink 3 Hypotonic cell will eventually burst E Dialysis the diffusion of certain solutes In comparison to osmosis the diffusion of a certain solvent F Solution types i Isotonic same no net movement ii Hypertonic quotmorequot nonpenetrating solutes iii Hypotonic quotlessquot nonpenetrating solutes G Factors that influence diffusion rate i Temperature 1 The higher the temp the greater the rate of diffusion ii Concentration gradient 1 The greater the concentration gradient the faster the rate of diffusion iii Sizeweight of molecules 1 The smaller the molecule the faster the rate of diffusion Concentration the amount of solute that is dissolved in a solvent Gradient a difference in properties Diffusion is in response to a concentration gradient 357 Active transport needs energy to diffuse transport proteins are required moves against its concentration gradient i Moves solutes against gradient requires energy i ATP supplies energy 1 Proteins span the entire membrane They often have a binding site for ATP and another binding site for the molecule They are referred to as PUMPS iii Ex SodiumPotassium pump 1 Move 3 Na out and 2 K in 2 Changes shape 3 quotmembrane potential a Makes the inside of the cell more and more quotnegativequot iv Electrogenic pump generates voltage v Proton pump actively transports proteins vi Cotransport couples downhill and uphill 1 Ex Sucrose H cotransport in plant cells 2 Needs ATP and Transport protein L The force driving simple diffusion is the concentration gradient while the energy source for active transport is ATP IV Endocytosis and Exocytosis A Endocytosis cells importing large particles or substances i Pincocytosis quotcell drinking bringing in smaller molecules dissolved in materials ii Receptormediator endocytosis eating specific molecules iii Phagocytosis quotcell eating moves large particles or whole cells B Exocytosis moves material out of the cell