Cell biology week 6
Cell biology week 6 BSC322
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This 5 page Class Notes was uploaded by Sarah Ferrier on Saturday October 3, 2015. The Class Notes belongs to BSC322 at Marshall University taught by Dr. Harrison in Fall 2015. Since its upload, it has received 43 views. For similar materials see Cell Biology in Biology at Marshall University.
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Date Created: 10/03/15
E D D w 03 Chapter 7 membranes gt Length of fatty acid chain and degree of saturation both affect membrane fluidity gt Longer more saturated fatty acids have a higher TmS gt Shorter less saturated fatty acids have a lower TmS O 00 gt Intercalation of rigid cholesterol molecules into a membrane decreases its fluidity and increases Tm gt Fluidity buffer gt Decreases permeability of membrane toxins and small polar molecules V Localized regions of membrane lipids that are involved with cell signaling I Less fluid than rest of membrane Roles in detecting and responding to extracellular signaling Transport nutrients and ions across membranes Bind activated immune system cells to their microbial targets Transport cholera toxin into intestinal cells VVVV I Move specific substances across an otherwise impermeable membrane I Catalyze reactions associated with the membrane I On cell s surface mitochondria and chloroplasts gt Due to charge on ion and surrounding hydration shell gt Transport proteins act as either hydrophilic channels or carriers Hydrophobic regions embedded in the interior membrane bilayer Difficult to remove Integral monotropic proteins are embedded in just one side of bilayer Most are transmembrane proteins I Cross either once singlepass proteins or several times multipass proteins VVVV gt Anchored to lipid bilayer by one or more hydrophobic transmembrane segments gt Have Cterminus extending from one surface of the membrane to Nterminus on the other gt Glycophorin gt 220 transmembrane segments gt Proteins that lack discrete hydrophobic regions do not penetrate lipid bilayer gt These proteins are bound to membrane surfaces through weak electrostatic forces and hydrogen bonds gt Polypeptide chains of this protein are located on surfaces of membranes gt Covalently bound to lipid molecules gt I Attached to saturated fatty acid I Synthesized in cytosol and then modified by addition of multiple isoprenyl groups gt I Covalently linked to glycosylphosphatidylinositol gt Membrane proteins with carbohydrate chains covalently linked to amino acid chains I Addition of carbohydrate side chain to a protein is glycosylation o Occurs in ER and Golgi compartments gt Most common monosaccharide is D glucose C6H1206 I Carbohydrate gt Two ring forms of Dglucose I Depend on spatial orientation of hydroxyl group on carbon 1 gt Most prominent in plasma membranes gt Play role in celltocell recognition gt Carbohydrate groups protrude on outer surface of cell membrane Chapter 8 Transport across membranes Central aspect of cell function Movement of ions or small organic molecules dissolved gases solutes Movement of a solute across a membrane is determined by its concentration gradient or its electrochemical gradient gt The erythrocyte plasma membrane provides examples of transport mechanisms VVV gt Direct unaided movement dictated by differences in concentration of solute on two sides of the membrane I Direction dictates by differences in concentrations gt Diffusion always moves solutes toward equilibrium gt Limited to small nonpolar molecules gt Rate is directly proportional to concentration gradient gt Diffusion of water across selectively permeable membranes gt Water molecules are uncharged and unaffected by membrane potential I Moves from regions of low to high solute concentration and from high to low water concentration gt If two solutions are separated by selectively permeable membrane permeable to water but not solutes water will move toward region of higher solute concentration gt Assist most solutes across membrane gt Some move solutes to regions of lower concentration 0 Passive transport 0 Uses no energy 0 Proteinmediated movement down the gradient 0 Exergonic Analogous to enzymes Competitive inhibition can occur MichaelisMenten Bind on or more solute molecules on one side of membrane and then undergo a conformational change that transfers the solute to the other side of the membrane 0 Shields polar or charged groups of the solute from the nonpolar interior of membrane Alternate between two conformational stages o Allosteric protein Transport either one or two solutes 0 Single solute 0 Two solutes are transported simultaneously gt same direction gt opposite direction Erythrocyte glucose transporter GLUT and anion exchange protein are examples 0 Glucose concentration kept low 0 Once phosphorylated glucose cannot bind carrier protein locked in cell 0 Hexokinase Form hydrophilic channels through the membrane that allow the passage of solutes without a major change in the conformation of the protein Relatively large unspecific Pores ion channels Facililtate diffusion by forming hydrophilic transmembrane channels 0 transmembrane proteins that allow rapid passage of specific ions 0 transmembrane proteins that allow rapid passage of various solutes o Pores on outer membranes of bacteria mitochondria and chloroplasts are larger less specific than ion channels 0 Beta barrels o transmembrane channels that allow rapid passage of water Erythrocytes kidney cells Root cells vacuolar membranes Tetrameric integral membrane proteins 999 24 transmembrane segments gt Proteinmediated movement up a concentration gradient or against an electrochemical concentration I Accumulation of solute molecules or ions on one side of the membrane coupled with the hydrolysis of ATP 0 ATPases ATPase pumps I NaK pump I Requires energy but depends on transport of two solutes 0 One solute down its gradient and the other up its gradient I Driven by protein gradient I Nagucose symporter gt Allow passage of specific ions gt Gated I Open and close in response to stimulus 0 Voltage 0 Ligand o Mechanosensitive I Reversiny phosphorylated by ATP I 810 transmembrane segments I on gradients I Protein pumping I Plasma membrane I Vacuoles organelles I Protein pumping I Bacteria mitochondria chloroplasts I Big motor I Gradients can be used as energy source to synthesize ATP 0 ATP synthases I Proton channel I transporters I Embedded in membrane I Peripheral proteins I 4 polypeptides I Resistance to drugs Chapter 9 qucolysis o 9 gt Oxygen comes from glucose gt Sugar broken into two gt Requires energy gt Energy and available energy stores energy electrons gt Energy into pyruvate
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