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Topic: Facilitated diffusion

	Facilitated Diffusion
		Their transport must therefore be "facilitated" by proteins that span the membrane and provide an alternative route or bypass.
		Facilitated diffusion is the name given this process.
		It is similar to simple diffusion in the sense that it does not require expenditure of metabolic energy and transport is again down an electrochemical gradient.
	arbl.cvmbs.colostate.edu /hbooks/cmb/cells/pmemb/diffusion_f.html (365 words)

	Diffusion, facilitated transport, osmosis, and active transport.
		Diffusion is the movement of molecules from an area where the molecule is in high concentration to an area where the molecule is in lower concentration.
		Facilitated diffusion is the movement of a molecule from an area of high concentration to an area of lower concentration with the help of a protein channel or carrier.
		In the facilitated diffusion animation both amino acids and glucose are shown entering the cell facilitated by a protein carrier.
	www.coolschool.ca /lor/BI12/unit4/U04L03.htm (467 words)

	Facilitated diffusion
		Facilitated diffusion (facilitated transport) is a process of passive transport (diffusion) via which molecules diffuse across membranes, with the help of transport proteins (mediated transport).
		In contrast to active transport, facilitated diffusion does not require energy and carries molecules or ions down a concentration gradient.
		The transport proteins participating in facilitated diffusion resemble enzymes.
	www.ibpassociation.org /encyclopedia/Chemistry/Facilitated_diffusion.php (267 words)

	Transport Across Cell Membranes
		The diffusion of water through the plasma membrane is of such importance to the cell that it is given a special name: osmosis.
		Note that in all cases of facilitated diffusion through channels, the channels are selective; that is, the structure of the protein admits only certain types of molecules through.
		Water passes by diffusion from a region of higher to a region of lower concentration.
	users.rcn.com /jkimball.ma.ultranet/BiologyPages/D/Diffusion.html (2794 words)

	Microbiology and Bacteriology :: The world of microbes
		However, the cell boundary is the membrane and its hydrophobic core prevents this diffusion for polar molecules.
		Facilitated diffusion, as shown in Figure 2-21, is therefore specific because a protein must bind the molecule.
		One example of a protein involved in facilitated diffusion is the glycerol facilitator protein.
	www.bact.wisc.edu /Microtextbook/index.php?module=Book&func=displayarticle&art_id=48 (1113 words)

	BC Online: 6A: Passive and Facilitated Diffusion
		This process is called facilitated diffusion and represents a physical as opposed to chemical process since no covalent bonds are made or broken.
		Passive (non-facilitated) diffusion is kinetically slow in the absence of a receptor since membranes present formidable barriers to the passage of polar molecules.
		This mechanism does not fit the criteria of facilitated diffusion since the required protein fragment is not a classical receptor.
	employees.csbsju.edu /hjakubowski/classes/ch331/transkinetics/oldiffusioneq.html (2418 words)

	Transport Across Membranes (Site not responding. Last check: )
		Diffusion is the random movement of dissolved substances and solvent molecules.
		The facilitated diffusion part is due to a dependence on movement only with the concentration gradient and a mechanism of passage through the membrane which employs membrane proteins.
		Facilitated diffusion, on the other hand, is movement directly across a membrane and directly into the cytoplasm if that membrane is a plasma membrane.
	www.mansfield.ohio-state.edu /~sabedon/biol1055.htm (2774 words)

	Chapter 1 - Diffusion and Transport
		Diffusion of water has no effect upon the diffusion of other substances, but during osmosis, dissolved substances can get swept up in the stream of water and moved faster than would be expected from their diffusion alone.
		Glucose can get through the membrane by diffusing through the pores (its diameter is approximately that of the largest ones), but the rate at which it enters most cells is higher than one would expect for diffusion.
		Glucose is removed from the cell by facilitated diffusion, and water follows along with both sodium and glucose in order to keep its concentrations in equilibrium (see osmosis earlier in this chapter).
	www.unmc.edu /Physiology/Mann/mann1.html (4182 words)

	The Microbial World :: They rule
		However, the cell boundary is the membrane and its hydrophobic core prevents this diffusion for polar molecules.
		Facilitated diffusion, as shown in Figure 2-21, is therefore specific because a protein must bind the molecule.
		One example of a protein involved in facilitated diffusion is the glycerol facilitator protein.
	www.microbiologytext.com /index.php?module=Book&func=displayarticle&art_id=48 (1108 words)

	Facilitate Diffusion Animation (Site not responding. Last check: )
		Other mechanisms of facilitated diffusion are also possible.
		When we are dealing with facilitated diffusion, the protein allows molecules or ions to enter or leave the cell moving DOWN their concentration gradient.
		However, there is a transport protein which functions by facilitated diffusion which allows glucose to freely pass back and forth across the membrane.
	bio.winona.edu /berg/ANIMTNS/FacDiff.htm (264 words)

	Chapter 5 - Passive transport: facilitated diffusion (Site not responding. Last check: )
		Facilitated diffusion is the diffusion of a substance across a membrane.
		It is "facilitated" because a transport protein in the membrane enhances the transport of the substance across the membrane.
		Glucose, which is needed in large amounts by cells for energy, is one substance commonly transported into cells by facilitated diffusion.
	w3.dwm.ks.edu.tw /bio/activelearner/05/ch5c3.html (97 words)

	[No title] (Site not responding. Last check: )
		Facilitated diffusion is a process whereby a substance passes through a membrane with a aid of an intermediary or a facilitator.
		The facilitator is an integral membrane protein that spans the width of the membrane.
		The purpose of this paper is to consider the possibility that H+ channels are expressed at high levels in alveolar epithelial cells for the purpose of facilitating CO2 extrusion by the lung.
	www.lycos.com /info/facilitated-diffusion--membrane.html (472 words)

	Concept 4 Review: Comparing Facilitated Diffusion and Active Transport
		This process is called passive transport or facilitated diffusion, and does not require energy.
		For example, red blood cells rely on facilitated diffusion to move glucose across membranes, whereas intestinal epithelial cells use active transport to take in glucose from the gut.
		Facilitated diffusion is effective for red blood cells because the concentration of glucose in the blood is stable and higher than the cellular concentration.
	www.phschool.com /science/biology_place/biocoach/biomembrane1/diffusion.html (199 words)

	DIFFUSION THROUGH A CELL MEMBRANE
		Diffusion is random movement of molecules but has a net direction toward regions of lower concentration in order to reach an equillibrium.
		Since the net movement of diffusing molecules depends on the concentration gradient, the rate of diffusion is directly proportional to the concentration gradient (dC/dx) across the membrane.
		Facilitated diffusion, however, approaches a maximum rate as the carrier proteins become saturated with solute.
	www.tiem.utk.edu /~gross/bioed/webmodules/diffusion.htm (930 words)

	The Major Biological Transport Mechanisms Page
		In the case of "facilitated" diffusion, the diffusion of a solute particle across a membrane is faster than can be explained simply by the existing concentration gradient for the solute...
		Facilitated diffusion of glucose and amino acids: Glucose is a small monosaccharide which diffuses into cells down its concentration gradient, but at a rate that is greater than can be explained by the glucose concentration gradient, alone.
		In addition, facilitated diffusion can occur in any direction across a membrane, but will always move solutes from an area of high concentration to an area of low concentration (i.e..
	faculty.etsu.edu /currie/biotransport.htm (758 words)

	Membrane Transport Mechanisms (Site not responding. Last check: )
		Facilitated diffusion utilizes membrane protein channels to allow charged molecules (which otherwise could not diffuse across the cell membrane) to freely diffuse in a nd out of the cell.
		The speed of facilitated transport is limited by the number of protein channels available, whereas the speed of diffusion is dependent only on the concentration gradient.
		Similarly to facilitated transport, active transport is limited by the number of protein transporters present.
	web.mit.edu /esgbio/www/cb/membranes/transport.html (738 words)

	[No title] (Site not responding. Last check: )
		In facilitated diffusion a protein (shown in green)serves as a channel for diffusing molecules(red) that otherwise would not be able to pass through the cell membrane.
		The proteins involved in facilitated diffusion are not actively pumping the molecules through.
		that since facilitated diffusion is simply diffusion involving a protein to make diffusion happen more easily across a cell membrane, this process cannot concentrate substances in a cell beyond that in the surrounding environment.
	staff.jccc.net /pdecell/cells/facildiff.html (149 words)

	Proboscis \| Diffusion
		Diffusion began life back in 1999 as a response to the increasing difficulty that I was having in distributing the books and journals I was then publishing – both for Proboscis and for the Royal College of Art’s Computer Related Design Research Studio.
		Diffusion then became a research project to devise a paper folding and layout format that could be used to create small files using Adobe’s PDF file format.
		DIFFUSION is brought to you by Proboscis, a non-profit organization.
	diffusion.org.uk (4389 words)

	[No title]
		Physiological Significance-- The transport and facilitated diffusion of oxygen and other ligands by Hbs have been subjects of investigation since the 1960s (47, 48).
		Facilitated diffusion is the transport of substances across a membrane by a trans-membrane protein molecule.
		Like normal diffusion, facilitated diffusion, which transports materials across a membrane, is driven by potential energy of a concentration gradient.
	lycos.com /info/facilitated-diffusion.html (370 words)

	Cell Membranes
		Diffusion is the movement of a substance (atoms, molecules, or ions) down its own concentration gradient.
		The net result of diffusion is that substances become evenly distributed (dynamic equilibrium) and potential energy reaches zero.
		Diffusion is fastest when the concentration gradient is largest, but diffusion slows rapidly as the distance from the membrane barrier increases since concentration gradients decrease sharply.
	home.earthlink.net /~dayvdanls/cell_membranes.htm (1371 words)

	Diffusion (Site not responding. Last check: )
		There are three main types of diffusion: simple, channel, and facilitated diffusion.
		Facilitated diffusion is a type of passive transport that is dependent on single transport protein carriers.
		Facilitated diffusion is non-diffusional because the molecule moves along with the carrier.
	biology.kenyon.edu /HHMI/Biol113/diffusion.htm (207 words)

	[No title]
		The distinctive feature of literary transmissions, and all diffusions through individuals except during mass migrations, is that they tend to be largely confined to elites, or, where not, to enclaves of non-elite persons cut off from the mass of their societies.
		This was true of the diffusion of Hellenism in the Mediterranean world and was largely true of the imperial influence on the societies of Asia and Africa.
		It is simply not true that the diffusion of Western culture, especially at the popular level, leads to the homogenization of the culture of the world.
	www.warholfoundation.org /paperseries/article2.htm (7758 words)

	Cell Membranes Problem Set
		Simple diffusion can only move material in the direction of a concentration gradient; facilitated diffusion moves materials with and against a concentration gradient.
		Simple diffusion is found only in prokaryotes while facilitated diffusion is found only in eukaryotes.
		Diffusion means that the net movement of particles (molecules) is from an area of high concentration to low concentration.
	www.biology.arizona.edu /cell_bio/problem_sets/membranes/07t.html (295 words)

	--Chapt. 4, Diffusion and Cell Membranes
		47. The rate of facilitated diffusion of a molecule across a membrane does not continue to increase as the concentration difference of the molecule across the membrane increases because
		diffusion) is called __________ transport and the movement of molecules across the membrane in which energy (i.e.
		52. Osmosis is the diffusion of water (diffusion is a more general term for the movement of molecules along a concentration gradientÄÄfrom high to low concentration).
	www.valdosta.edu /~bergstrm/audesrk4.htm (2394 words)

	Lecture Notes-9
		Facilitated diffusion cannot cause net transport of molecules from a low to a high concentration- this would require input of energy
		The Na concentration gradient is used to produce secondary transport of sugars and amino acids (facilitated diffusion)
		Note that most of the special properties of facilitated and active transport (those checked "yes") are due to the protein nature of the transport molecules.
	members.aol.com /Bio50/LecNotes/lecnot09.html (1114 words)

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