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Topic: Membrane transport

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	cellmembrane
		Proteins on the inside surface of cell membranes are often attached to the cytoskeleton and are involved in maintaining the cell's shape, or in cell motility.
		Passive transport is the transport of substances across a membrane by a trans-membrane protein molecule.
		This transport protein is present in the cell membranes of all animal cells and is the most abundant and important of all membrane pumps.
	www.biologymad.com /cells/cellmembrane.htm (1771 words)

	Transport Across Cell Membranes
		The transport of macromolecules through membranes is described in Endocytosis.
		This homotrimer in the outer membrane of E.
		Perhaps some molecules are passed through the membrane by a conformational change in the shape of the transmembrane protein when it binds the molecule to be transported.
	users.rcn.com /jkimball.ma.ultranet/BiologyPages/D/Diffusion.html (2794 words)

	Botany online: Membranes and Transport
		Exchange of molecules through membranes depends on highly specific transport systems, prominent representatives of this group are the porines that extensively have been studied in bacteria.
		Membranes separate reaction areas that can be distinguished due to their chemical composition, their pH value and their electric potential.
		Active transport can be understood when knowing structure and function of integral proteins and the electrochemical properties of the membrane while the understanding of energy transformation requires information about all the molecules within the respective membrane.
	www.biologie.uni-hamburg.de /b-online/e22/22.htm (1136 words)

	Brain and Behavior (IPHY 3730), University of Colorado at Boulder
		The plasma membrane of a nerve cell functions as a barrier between the cytoplasm and the extracellular environment of the cell.
		Membrane proteins in a nerve cell have a number of specific functions, such as permitting selective passive of an ion (=ion channel), moving an ion against a concentration gradient (=ion pump), or acting as a receptor which communicates information about events in the immediate environment.
		Membrane transport of solute (such as glucose or Na+) is by either diffusion (passive, down a concentration gradient), facilitated diffusion (passive, mediated, down a concentration gradient, or active transport (requiring energy, mediated, but movement against a concentration gradient).
	www.colorado.edu /kines/Class/IPHY3730/03plasmamembrane.html (1723 words)

	Membrane transport
		Transport of nutrients, ions, and excretory substances from one side to the other is a major function of the cell membrane.
		Membranes transport molecules too big to permeate the membrane by engulfing the substance and forming internal vesicles.
		Mechanism: foreign particles are coated with antibodies Þ a complement reaction labels antibody for recognition by the antibody receptors in the membrane of macrophages Þ formation of pseudopodia Þ particles are engulfed by binding of antibodies by receptors.
	fajerpc.magnet.fsu.edu /Education/2010/Lectures/12_Membrane_Transport.htm (1302 words)

	Cell Membranes
		What makes the membrane truly special is the presence of different proteins on the surface that are used for various functions such as cell surface receptors, enzymes, surface antigens, and transporters.
		Some specific examples of transport membranes are channel proteins, which allow solutes to cross if they are the correct size and charge.
		An example of active transport is the sodium-potassium pump, which in conjunction with the potassium leak channel, allows the cell the control it's membrane potential.
	library.thinkquest.org /C004535/cell_membranes.html (630 words)

	Membranes and Membrane Transport
		Transport of permeable molecules is generally by passive diffusion, random movement from areas of high to low concentration in response to a concentration gradient.
		Transport of impermeable molecules is generally by either facilitated diffusion (along the concentration gradient, and therefore not requiring an input of energy), or by active transport (an energy-subsidized process by which materials can be pumped across a membrane against their concentration gradient).
		Carriers are small molecules which dissolve in the membrane and either bind and release the transported substrate or form pores through which the substrate can pass from one side of the membrane to the other.
	home.austin.rr.com /mikeready/Membrane_Transport.htm (1038 words)

	Mechanisms for Transport Across Membranes (Site not responding. Last check: 2007-10-17)
		is driven by the kinetic energy of the molecules being transported or by membrane transporters by facilitate crossing.
		A molecule or ion that crosses the membrane by moving down a concentration or electrochemical gradient and without expenditure of metabolic energy is said to be transported passively.
		Transport of uncharged species across a membrane is dictated by differences in concentration of that species across the membrane - that is, by the prevailing concentration gradient.
	arbl.cvmbs.colostate.edu /hbooks/cmb/cells/pmemb/transport.html (329 words)

	Membrane Transport Mechanisms (Site not responding. Last check: 2007-10-17)
		The center of the barrel could constitute a hole in the plasma membrane that is isolated from the lipid bilayer by an array of transmembrane domains around it.
		In practice, given the structure of known membrane proteins, these holes are only large enough to allow the passage of small molecules through the plasma membrane, almost always simple ions like hydrogen, potassium or sodium.
		Primary active transport involves using energy (usually through ATP hydrolysis) at the membrane protein itself to cause a conformational change that results in the transport of the molecule through the protein.
	web.mit.edu /esgbio/www/cb/membranes/transport.html (738 words)

	McMaster Chemistry: Membrane Research Group (Site not responding. Last check: 2007-10-17)
		The membrane research group at McMaster University is involved in the preparation, characterization, evaluation and modelling of a wide range of membranes and membrane separation processes.
		Existing membranes are being studied for the separation of organics and inorganics from water, and design of membrane systems using reverse osmosis/nanofiltration and pervaporation membranes; particularly for environmentally important applications.
		The membrane group and the university have the facilities to analyze all facets of the membrane research from chemical analysis of monomers to surface and performance analysis of the membranes.
	www.chemistry.mcmaster.ca /membrane (1521 words)

	Plasma Membrane (Site not responding. Last check: 2007-10-17)
		As mentioned previously the plasma membrane is composed of a bilayer.
		The plasma membrane is assymetric with respect to the lipid distribution.
		Another example of an active mediated transport is the transport of Na out of the cell and the simultaneous import of K
	www.prism.gatech.edu /~gh19/b1510/memtra.htm (2182 words)

	[No title]
		- Transport of substances is necessary to maintain a relatively constant internal environmentÑhomeostasis - Cells have membranes or plasmalemma that serve as barriers between the ECF (extracellular fluid = fluid outside the cells & ICF (intracellular fluid = fluid inside the cells).
		A uniport is a protein transporter that carries only one substrate, and a cotransport protein is one that moves 2 (or 3) different molecules at the same time; symport is when the molecules are transported in the same direction; antiport is when the molecules are transported in the opposite directions.
		Transporting epithelial cells, such as the those of the kidney & intestine, are said to be polarized because they have different membrane proteins on their apical & basal surfaces.
	www.angelo.edu /faculty/rwilke/Bio1410/membrane.doc (1932 words)

	Active transport - Wikipedia, the free encyclopedia
		Active transport is the mediated transport of biochemicals, and other atomic/molecular substances, across membranes.
		In primary transport, energy is directly coupled to the movement of a desired substance across a membrane independent of any other species.
		One of these species is allowed to flow from high to low concentration which yields the entropic energy to drive the transport of the other solute from a low concentration region to a high one.
	en.wikipedia.org /wiki/Active_transport (463 words)

	5 Membrane Transport Mechanisms
		Active transport requires the expenditure of energy to transport the molecule from one side of the membrane to the other, but active transport is the only type of transport that can actually take molecules up their concentration gradient as well as down.
		Similarly to facillitated transport, active transport is limited by the number of protein transporters present.
		Secondary active transport involves using energy to establish a gradient across the cell membrane, and then utilizing that gradient to transport a molecule of interest up its concentration gradient.
	www.bgsu.edu /departments/chem/midden/MITBCT/mem/transport.html (738 words)

	Membrane transport systems as couplers of metabolic pathways
		Membrane proteins are the 'enzymes' which facilitate the transport of metabolic intermediates between cell compartments as well as into and out of the cell.
		Facilitated transport is tightly coupled to the chemical potential of metabolites or a group of metabolites (representing a pathway).
		The inner mitochondrial membrane is an important selective barrier that controls the coupling of the central respiratory energy producing pathways - citric acid cycle and oxidative phosphorylation - with carbohydrate, fat, and amino acid metabolism.
	www.whatislife.com /reader2/Metabolism/pathway/transport.html (1991 words)

	Membrane transport lab
		Since there are a limited number of carrier molecules which transport a particular particle through a cell membrane, carrier proteins can be saturated (full) with particles waiting to move across the membrane.
		Active transport is similar to facilitated diffusion except that energy is required.
		Active transport is used to move particles against a concentration gradient, or from lower concentrations to higher concentrations.
	csm.jmu.edu /biology/danie2jc/membrane_transport_lab.htm (1247 words)

	Liquid Membranes - Transport (Site not responding. Last check: 2007-10-17)
		I am not going to walk you through basic transport phenomenon now, but it is good to know that there are four basic types of transport systems, each of which has its own mechanisms and carrier types.
		At the Phase I interface of the membrane, the guest salt is complexed with the carrier.
		As you can see in Figure 10, anionic transport is similar in mechanism to the cationic transport, save for the use of a cationic carrier instead of an anionic one in the antiport configuration.
	www.rpi.edu /dept/chem-eng/Biotech-Environ/patillo/membrane.biochem/mem.transport.html (435 words)

	SparkNotes: Cell Membranes: Structures Responsible for Membrane Transport
		In addition to these two forms of transport, there exist other forms of transport such as endocytosis and exocytosis, which will be discuss later and do not require the same set of membrane proteins for their function.
		Active transport occurs when a cell actively pumps a molecule across its membrane, against the natural direction dictated by diffusion, osmosis, or polarity.
		Transport proteins are critical to cell life and cell interactions.
	www.sparknotes.com /biology/cellstructure/cellmembranes/section3.rhtml (487 words)

	TRANSPORT IN AND OUT OF CELLS
		Development of a cell membrane that could allow some materials to pass while constraining the movement of other molecules was a major step in the evolution of the cell.
		Cell membranes are differentially (or semi-) permeable barriers separating the inner cellular environment from the outer cellular (or external) environment.
		In the case of active transport, the proteins are having to move against the concentration gradient.
	www.emc.maricopa.edu /faculty/farabee/BIOBK/BioBooktransp.html (2173 words)

	SparkNotes: Cell Membranes: Terms
		Active transport - The transport of molecules across a membrane and against their natural flow; mediated by carrier proteins and requiring outside energy.
		Transport is carried out by a conformational change that occurs within the protein that forms an opening for specific molecules to pass through.
		Transport is carried out by its membrane-spanning hydrophilic structure which, when open, allows molecules to pass through.
	www.sparknotes.com /biology/cellstructure/cellmembranes/terms.html (404 words)

	webmembranetransport
		Whenever a substance is unable to cross the membrane because it may be to large to pass through the pores, unable to dissolve in the bilipid membrane core, or required to move against rather than with a concentration gradient.
		Active transport systems are also distinguished according to the source of energy that drives the transport.
		This is similar to phagocytosis except the plasma membrane surrounds a tiny droplet of extracellular fluid.
	www.etsu.edu /cpah/hsci/forsman/membranetransport.htm (1058 words)

	Functions of the Plasma Membrane
		The plasma membrane is a very important structure which functions to allow certain substances to enter or leave the cell.
		Both the protein portion and the phospholipid portion of the membrane are involved in the permeability.
		This is similar to simple diffusion in the sense that it is diffusion (across a membrane) from a high concentration to a lower concentration.
	io.uwinnipeg.ca /~simmons/cm1503/membranefunction.htm (563 words)

	Proteins of the Cell (Site not responding. Last check: 2007-10-17)
		Also there are two basic types of cotransport: symport, which is where two molecules are transported in the same direction and antiport, where the molecules are transported opposite directions through the membrane (which will be shown by the Na - K ATPase pump coming up).
		This transport, which will require energy, is going against the electro-chemical gradient.
		Putting these all together in a membrane is done in the following example of the Sodium-Potassium ATPase pump in conjunction with the Potassium leak, and the glucose symport with Sodium.
	cbri.umn.edu /~mwd/cell_www/chapter2/protein.html (329 words)

	Summary of Transport Mechanisms
		The binding causes a conformation change, which allows the transported substance to be released on the other side of the membrane.
		The glucose transporter is a widespread and important example of this type of transporter, especially since insulin controls the number of these transporters working in certain cells.
		Active transport is similar to the preceding two mechanism in that specific binding of the transported substance occurs.
	courses.washington.edu /conj/membrane/transport.htm (1329 words)

	Lecture 14 and 15, Transport
		The mitochondrial family of metabolite transporters seem to have a conserved secondary structure, with three well defined hydrophobic spans which are likely tranmembrane helices, and a fourth span with hydrophobic and amphipathic character, which might also be transmembrane.
		Transport of Ca plays a physiological role in those cell processes which are activated or inhibited by changes in Ca activity in the cytoplasm.
		In the presence of a transportable anion (phosphate), or the anion of a permeable weak acid (eg.
	www.life.uiuc.edu /crofts/bioph354/lect14&15.html (2711 words)

	ScienceDaily: UCLA Researcher First To Solve Structure Of Membrane Transport Protein
		Membrane Protein Research Yields New Insights Into Inner Workings Of The Cell (June 28, 2000) -- Biophysicists at the National Science Foundation's National High Magnetic Field Laboratory in Tallahassee, Florida, have discovered that membrane proteins give rise to unique patterns of signals in...
		Scientists Devise Method To Study Membrane Proteins, One Key To Drug Discovery (April 9, 2004) -- Scientists at the University of Virginia Health System have come up with a protocol to extract proteins from membranes by using chemicals that allow them to be reversibly folded and...
		Cholesterol -- Cholesterol is a sterol and a lipid found in the cell membranes of all body tissues, and transported in the blood plasma of all animals.
	www.sciencedaily.com /releases/2003/08/030814072338.htm (1395 words)

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