move from high to low concentration · 2011-11-17 · diffusion osmosis movement of water ......
TRANSCRIPT
2011
Move from HIGH to LOW concentration-“passive transport”
-no energy needed
diffusion osmosis
movement of water
Diffusion through protein channels◦ channels move specific molecules across
cell membrane
◦ no energy needed
“The Bouncer”
open channel = fast transport
facilitated = with help
HIGH
LOW
Cells may need to move molecules againstconcentration gradient-conformational shape change transports solute from
one side of membrane to other -protein “pump”-“costs” energy = ATP conformational change
ATP
LOW
HIGH
symportantiport
Many models & mechanisms
ATP ATP
Membrane potentialthe voltage difference across a membrane
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Electrochemical gradientcaused by the concentration electrical gradient of ions across a membrane
Electrogenic pumpa transport protein that generates the voltage across a membrane
CotransportOccurs when active transport of a
specific solute indirectly drives the active transport of another solute
7
Involves transport by a membrane protein
Driven by a concentration gradient
Where else have you seen this concept?
Cotransport: active transport driven by a concentration gradient
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Where else have you seen this?
Passive TransportSimple diffusion
diffusion of nonpolar, hydrophobic moleculeslipids
HIGH LOW concentration gradient
Facilitated transport diffusion of polar, hydrophilic molecules
through a protein channel
HIGH LOW concentration gradient
Active transportdiffusion against concentration gradient
LOW HIGH
uses a protein pumprequires ATP ATP
simplediffusion
facilitated
diffusion
active
transport
ATP
Bulk transport across the plasma membrane occurs by:
exocytosis and endocytosisLarge proteins
Cross the membrane by different mechanisms
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How about large molecules?
Movement into & out of cell-through vesicles & vacuoles
Endocytosis: in phagocytosis = “cellular eating” pinocytosis = “cellular drinking” Recepter-mediated
Exocytosis: out
exocytosis
In exocytosisTransport vesicles migrate to the plasma membrane, fuse with it, and release their contents
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In endocytosisThe cell takes in macromolecules by forming new vesicles from the plasma membrane
http://www.youtube.com/watch?v=npYUjxWrhfo
http://www.youtube.com/watch?v=aWItglvTiLc&feature=related
http://www.youtube.com/watch?v=KxTYyNEbVU4&feature=related
forms new vesicles from the plasma membrane
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phagocytosis
pinocytosis
Receptor-mediated
Endocytosis
(1) phagocytosis: “cellular eating”
cell engulfs a particle: extends pseudopodia around it & packages it in a large vacuole.
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http://www.youtube.com/watch?
v=aWItglvTiLc&feature=related
http://www.youtube.com/watch?v=U9pvm_4-bHg
http://www.youtube.com/watch?v=JnlULOjUhSQ&feature=related
http://www.youtube.com/watch?v=JnlULOjUhSQ&feature=related
http://www.youtube.com/watch?v=pvOz4V699gk
http://www.youtube.com/watch?v=aWItglvTiLc&feature=related
(2) pinocytosis: “cellular drinking”
cell creates a vesicle around a droplet of extracellular fluid(non-specific process)
http://www.youtube.com/watch?v=v8XaY-
vVtcA&feature=results_main&playnext=1&list=PLF8E2635BAFF54082
(3) Receptor-mediated: very specifictriggered when extracellular substances bind to
receptors/ligands on the membrane surface, especially near coated pits
triggers formation of a vesicle