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Chapter 5

Chapter 5 membrane and transport.docx

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York University
BIOL 1000
Nicole Nivillac

Chapter 5 membranes and transport - Cystic fibrosis- caused by mutation of a gene in the cystic fibrosis transmembrane conductance regulator(CFTR) - CFTR is a transport pump which pumps chloride ions out of the cells in the lungs and intestinal tract. Structure of membranes - The development of the plasma membrane is an important part of evolution of the cell. - Plasma membrane- a selective permeable barrier. - Fluid mosaic model- model used to view the membrane structure - membranes are composed of fluid lipid molecules where proteins are embedded and float freely - many types of proteins along the plasma membrane - protein to lipid ratio in membranes vary on the type of membrane - membrane asymmetry- each side of the lipid bilayer have different components and proteins. - Receptor proteins- found outside of plasma membrane, proteins bind to receptor protein which causes change in proteins on the other side of the membrane. Lipid fabric of a membrane - Lipids are the foundation of all biological membranes - Phospholipids are domination in lipids - Phospholipids are all amphipathic- region where it is hydrophobic and hydrophilic - Hydrophobic region is non polar, contains fatty acids - Hydrophillic region is polar, containing a phosphate group linked to an alcohol or amino acid group which is charged - When phospholipid added to aqueous solution it forms a bilayer - Membrane fluidity depends on the build up of the phospholipid. - Unsaturated phospholipids are more dense and saturated phospholipids are less dense - more unsaturated the membrane, the lower the gelling temperature point. - When temperature increases, membranes may become too fluid and lose liquid. K ,Na ,Ca begin to freely diffuse along membrane - Organisms can adjuct fatty acid composition of their membranes so fluidity can be maintained. - When temps drop unsaturated fatty acids are produced using enzyme called desaturases. - Desaturases convert saturated fatty acids into unsaturated fatty acids during the product of saturated fatty acids - Sterol compounds also affect membrane fluidity(eg cholesterol) restrain movement of membrane at high temp and slows down gelling process at low temp Membrane proteins 1) Transport 2) Enzymatic activity 3) Signal transduction(eg receptor proteins that bind to specific chemicals which causes change on the other side of the cell causing transduction signals) 4) Attachment/recognition - All membrane proteins are either integral or peripheral membrane proteins - Integral membrane proteins are within the phospholipid bilayer, regions composed with nonpolar amino acids linked together by polar amino acids, composed of polytopic or monotypic proteins - Peripheral membrane proteins are on the surface of the membrane, held to the surface by non covalent bonds, most are on the inside of the cell. Some of them hold the integral membrane protein in place using the cytoskeleton. DOES NOT INTERACT WITH THE HYDROPHOBIC REGION Passive membrane transport - Passive tr
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