Lodish H. - Molecular Cell Biology (5ed, Freeman, 2003) (794361), страница 104
Текст из файла (страница 104)
Biochim. Biophys.Acta 1573:312–318.Perrimon, N., and M. Bernfield. 2001. Cellular functions of proteoglycans: an overview. Semin. Cell Devel. Biol. 12(2):65–67.Rosenberg, R. D., et al. 1997. Heparan sulfate proteoglycans ofthe cardiovascular system: specific structures emerge but how is synthesis regulated? J. Clin. Invest. 99:2062–2070.The Extracellular Matrix of Nonepithelial TissuesKramer, R. Z., J. Bella, B. Brodsky, and H.
M. Berman. 2001.The crystal and molecular structure of a collagen-like peptide witha biologically relevant sequence. J. Mol. Biol. 311:131–147.Mao, J. R., and J. Bristow. 2001. The Ehlers-Danlos syndrome:on beyond collagens. J. Clin. Invest. 107:1063–1069.Shaw, L. M., and B. R. Olsen. 1991. FACIT collagens: diversemolecular bridges in extracellular matrices. Trends Biochem.
Sci.16(5):191–194.Weiner, S., W. Traub, and H. D. Wagner. 1999. Lamellar bone:structure–function relations. J. Struc. Biol. 126:241–255.Adhesive Interactions Involving Nonepithelial CellsBartsch, U. 2003. Neural CAMs and their role in thedevelopment and organization of myelin sheaths. Front. Biosci.8:D477–D490.Brummendorf, T., and V. Lemmon.
2001. Immunoglobulin superfamily receptors: cis-interactions, intracellular adapters and alternative splicing regulate adhesion. Curr. Opin. Cell Biol. 13:611–618.Cukierman, E., R. Pankov, and K. M. Yamada. 2002. Cell interactions with three-dimensional matrices. Curr. Opin. Cell Biol.14:633–639.Durbeej, M., and K. P.
Campbell. 2002. Muscular dystrophiesinvolving the dystrophin-glycoprotein complex: an overview of current mouse models. Curr. Opin. Genet. Devel. 12:349–361.Geiger, B., A. Bershadsky, R. Pankov, and K. M. Yamada. 2001.Transmembrane crosstalk between the extracellular matrix and thecytoskeleton. Nature Rev. Mol.
Cell Biol. 2:793–805.Hobbie, L., et al. 1987. Restoration of LDL receptor activity inmutant cells by intercellular junctional communication. Science235:69–73.243Lawrence, M. B., and T. A. Springer. 1991. Leukocytes roll ona selectin at physiologic flow rates: distinction from and prerequisitefor adhesion through integrins. Cell 65:859–873.Lo, C. Gap junctions in development and disease. Ann. Rev. Cell.Devel. Biol. 10.1146/annurev.cellbio.19.111301.144309.
(Expectedto be published in 2003.)Reizes, O., et al. 2001. Transgenic expression of syndecan-1 uncovers a physiological control of feeding behavior by syndecan-3.Cell 106:105–116.Somers, W. S., J. Tang, G. D. Shaw, and R. T. Camphausen.2000. Insights into the molecular basis of leukocyte tethering androlling revealed by structures of P- and E-selectin bound to SLe(X)and PSGL-1. Cell 103:467–479.Stein, E., and M. Tessier-Lavigne. 2001. Hierarchical organization of guidance receptors: silencing of netrin attraction by Slitthrough a Robo/DCC receptor complex.
Science 291:1928–1938.Plant TissuesDelmer, D. P., and C. H. Haigler. 2002. The regulation of metabolic flux to cellulose, a major sink for carbon in plants. Metab. Eng.4:22–28.Iwai, H., N. Masaoka, T. Ishii, and S. Satoh. 2000. A pectin glucuronyltransferase gene is essential for intercellular attachment in theplant meristem. Proc. Nat’l. Acad. Sci. USA 99:16319–16324.Lord, E. M.
2003. Adhesion and guidance in compatible pollination. J. Exp. Bot. 54(380):47–54.Lord, E. M., and J. C. Mollet. 2002. Plant cell adhesion: a bioassay facilitates discovery of the first pectin biosynthetic gene. Proc.Nat’l. Acad. Sci. USA 99:15843–15845.Lord, E. M., and S. D. Russell. 2002. The mechanisms of pollination and fertilization in plants. Ann. Rev. Cell Devel.
Biol.18:81–105.Pennell, R. 1998. Cell walls: structures and signals. Curr. Opin.Plant Biol. 1:504–510.Ross, W. Whetten, J. J. MacKay, and R. R. Sederoff. 1998. Recent advances in understanding lignin biosynthesis. Ann. Rev. PlantPhysiol. Plant Mol. Biol. 49:585–609.Zambryski, P., and K. Crawford. 2000. Plasmodesmata: gatekeepers for cell-to-cell transport of developmental signals in plants.Ann. Rev. Cell Devel. Biol.
16:393–421.Growth and Use of Cultured CellsDavis, J. M., ed. 1994. Basic Cell Culture: A Practical Approach.IRL Press.Goding, J. W. 1996. Monoclonal Antibodies: Principles and Practice. Production and Application of Monoclonal Antibodies in CellBiology, Biochemistry, and Immunology, 3d ed. Academic Press.Kohler, G., and C. Milstein. 1975. Continuous cultures of fusedcells secreting antibody of predefined specificity.
Nature256:495–497.Shaw, A. J., ed. 1996. Epithelial Cell Culture. IRL Press.Tyson, C. A., and J. A. Frazier, eds. 1993. Methods in Toxicology. Vol. I (Part A): In Vitro Biological Systems. Academic Press. Describes methods for growing many types of primary cells in culture.7TRANSPORT OFIONS AND SMALLMOLECULES ACROSSCELL MEMBRANESAquaporin, the water channel, consists of four identical transmembrane polypeptides.The plasma membrane is a selectively permeable barrier between the cell and the extracellular environment.
Its permeability properties ensure thatessential molecules such as ions, glucose, amino acids, andlipids readily enter the cell, metabolic intermediates remain in the cell, and waste compounds leave the cell. Inshort, the selective permeability of the plasma membraneallows the cell to maintain a constant internal environment. In Chapter 5, we learned about the components andstructural organization of cell membranes. Movement ofvirtually all molecules and ions across cellular membranesis mediated by selective membrane transport proteins embedded in the phospholipid bilayer. Because different celltypes require different mixtures of low-molecular-weightcompounds, the plasma membrane of each cell type contains a specific set of transport proteins that allow onlycertain ions and molecules to cross. Similarly, organelleswithin the cell often have a different internal environmentfrom that of the surrounding cytosol, and organelle membranes contain specific transport proteins that maintainthis difference.We begin our discussion by reviewing some general principles of transport across membranes and distinguishingthree major classes of transport proteins.
In subsequent sections, we describe the structure and operation of specific examples of each class and show how members of families ofhomologous transport proteins have different properties thatenable different cell types to function appropriately. We alsoexplain how specific combinations of transport proteins indifferent subcellular membranes enable cells to carry out essential physiological processes, including the maintenanceof cytosolic pH, the accumulation of sucrose and salts inplant cell vacuoles, and the directed flow of water in bothplants and animals. Epithelial cells, such as those lining thesmall intestine, transport ions, sugars and other small molecules, and water from one side to the other.
We shall see how,in order to do this, their plasma membranes are organizedinto at least two discrete regions, each with its own set oftransport proteins. The last two sections of the chapter focuson the panoply of transport proteins that allow nerve cells togenerate and conduct the type of electric signal called anaction potential along their entire length and to transmitthese signals to other cells, inducing a change in the electricalproperties of the receiving cells.OUTLINE7.1 Overview of Membrane Transport7.2 ATP-Powered Pumps and the Intracellular IonicEnvironment7.3 Nongated Ion Channels and the RestingMembrane Potential7.4 Cotransport by Symporters and Antiporters7.5 Movement of Water7.6 Transepithelial Transport7.7 Voltage-Gated Ion Channels and thePropagation of Action Potentials in Nerve Cells7.8 Neurotransmitters and Receptor and TransportProteins in Signal Transmission at Synapses245246CHAPTER 7 • Transport of Ions and Small Molecules Across Cell Membranes7.1Overview of Membrane TransportThe phospholipid bilayer, the basic structural unit of biomembranes, is essentially impermeable to most watersoluble molecules, ions, and water itself.
After describing thefactors that influence the permeability of lipid membranes,we briefly compare the three major classes of membraneproteins that increase the permeability of biomembranes. Wethen examine operation of the simplest type of transportprotein to illustrate basic features of protein-mediated transport.
Finally, two common experimental systems used instudying the functional properties of transport proteins aredescribed.Few Molecules Cross Membranesby Passive DiffusionGases, such as O2 and CO2, and small, uncharged polar molecules, such as urea and ethanol, can readily move by passive(simple) diffusion across an artificial membrane composed ofpure phospholipid or of phospholipid and cholesterol (Figure7-1). Such molecules also can diffuse across cellular membranes without the aid of transport proteins. No metabolicenergy is expended because movement is from a high to alow concentration of the molecule, down its chemical con-GasesCO2, N2, O2SmallunchargedpolarmoleculesEthanolONH2LargeunchargedpolarmoleculesC NH2UreaPermeablePermeableH2 OWaterSlightlypermeableGlucose, fructoseImpermeableIonsK +, Mg2 +, Ca2 +, Cl −,HCO3−, HPO42 −ImpermeableChargedpolarmoleculesAmino acids, ATP,glucose 6-phosphate,proteins, nucleic acidscentration gradient.
As noted in Chapter 2, such transportreactions are spontaneous because they have a positive Svalue (increase in entropy) and thus a negative G (decreasein free energy).The relative diffusion rate of any substance across a purephospholipid bilayer is proportional to its concentration gradient across the layer and to its hydrophobicity and size;charged molecules are also affected by any electric potentialacross the membrane (see below). When a phospholipid bilayer separates two aqueous compartments, membrane permeability can be easily determined by adding a small amountof radioactive material to one compartment and measuringits rate of appearance in the other compartment. The greaterthe concentration gradient of the substance, the faster its rateof diffusion across a bilayer.The hydrophobicity of a substance is measured by itspartition coefficient K, the equilibrium constant for itspartition between oil and water.
![](https://s.studizba.com/z.php?f=/templates/si/i/noavatar.png&w=100&h=100&t=1"){kind=avatar}
