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47 Cards in this Set
- Front
- Back
Speed of H20
Speed of C6H12O6 |
2500km/h (1500mi/hr)
850km/h |
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Flux
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Amount of material crossing a surface in a unit of time
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Net flux
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Difference between two one-way fluxes
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Diffusion equilibrium
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equal numbers of molecules diffuse in both directions
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Three types of fluxes
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2 one-way fluxes in opposite directions
Net flux |
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_____ always proceeds from regions of higher concentration to lower concetration (most important)
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Net flux
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Magnitude of net flux depends on:
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1: temperature (higher temp, highter nf 2: mass-greater mass, lower speed, smaller net flux 3:surface area-greater sa, great nf 4: medium-air easier than h20
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Bulk flow
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Circulatory system pumps(heart) materials rapidly over large distances
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Permeability coefficient
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(P) ease w/ which molecule able to move through a membrane
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Net Flux equation
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J=PA(Co-Ci)
A=surface area P=permeability coefficient Co-Constant extracellular concentration Ci-intracellular concentration |
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___diffuse slowly or not, ____diffuse rapidly(have large permeability constants
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Polar molecules
Nonpolar molecules |
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Membrane Potential
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separation of electrical charge that exists across plasma membranes
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Most cells have a _____ charge on the inside
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Negative
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The direction and magnitude of ion fluxes depend on _____ and _______
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concentration difference
electrical difference |
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Electrochemical gradient
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Concentration difference and membrane potential
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Channel gating
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Process of opening and closing ion channels
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Three factors altering channel protein conformations
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1: ligand-gated channels
2: Voltage-gated channels 3: Mechanically-gated channels |
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Ligand-gated channels
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specific molecules bind to channel proteins-directly/indirectly allosteric/covalent change in shape
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Voltage-gated channels
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Changes in membrane potential
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Mechanically-gated channels
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Physically deforming the membrane
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T/F
Membranes can have all 3 kinds of channels |
True
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Transporters
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Nondiffusional movements of iions medicated by integral membrane proteins called:
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Process of mediated transport
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Solute binds to site on transporter, transporter changes shape-exposes same site to solution on opposite side. sbstance dissociates
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Ion Channels
Both Transporters |
Move more ions/unit, continuous flow
membrane proteins & chemical specificity Must change shape-not as many ions pass |
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T/F
Proteins that transport amino acids also transport sugars. |
False
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3 factors determine magnitude of solute flux
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1: Extent of saturation
-depends on both solute conc. and affinity for solute 2: # transporters in membrane 3: rate @ which conformational change occurs |
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2 types of mediated transport
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Facilitated diffusion
Active Transport |
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Facilitated diffusion moves solutes ______ and active transport moves them _____
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Downhill
Uphill |
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Why doesn't glucose concentration in cells become equal to outside with facilitated diffusion?
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Once on the inside, glucose is immediately converted to Glucose-6-Phosphate
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How does insulin affect glucose transporters?
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Insulin increases the # of transporters in membrane
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Diabetes melitus
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Muscle and adipose tissue can't efficiently import glucose-high ECF glucose
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Active Transport
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Moves solutes against electrochemical gradient-ATP
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Similarities of active and facilitated transport
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requires substance binding to transporter.
Specificity and saturation |
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2 types of energy coupling
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1: Primary active transport
2: Secondary active transport |
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ATPase
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catalyzes the breakdown of ATP-phosphorylates itself
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Na+/K+ ATPase pump
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Sodium out and K in
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Na/K pump function
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1: Transporter w/ATP binds 3 Na+ ions @ high affinity sites
2: Binding results in activation of ATPase causing phosphorylation, releases ADP. 3: Phosphorylation-change in transporter-Na+ exposed to ECF, reduces affinity-released 4: New conformation increases 2 binding sites for K+ on EC surface 5: K+ binding dephosphorylates transporter-reduces affinity for K+-original conformation-now Na+ can be bound again. |
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Three other pumps
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Ca2+ATPase
H+ATPase H+/K+ATPase |
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Ca2+ATPase
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In plasma membrane. Ca2+ from cytosol to ECF-why Ca in cells is low-10^-7mol/L
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H+ATPase
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in plama membrane, inner mitochondrial/lysosomal membranes. H+ATPase moves H out of cells-maitain pH
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H+/K+ATPase
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In plasma membrane of stomach and kidneys-1H out and 1K+ in/1ATP
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Secondary Active Transport
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Uses electrochemical gradient as energy source, not phosphorylation-one substances moves down it's gradient and the other uphill.
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Transporters that mediate secondary active transport have ____ binding sites one for a/an ____ and another for _____
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2
ion cotransported molecule |
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Process of Secondary Active transport (Na+)
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High affinity sites for sodium on EC surface. Sodium binds, increasing affinity of binding site for transported solute-conformational change, exposing sites to IC side, Sodium detaches to ICF by diffusion down electrochemical gradient, affinity decreases releasing solute
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What determines creation and maintenance of electrochemical gradient?
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Primary active transporters
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Cotransport
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Movement in same direction
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Countertransport
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Movement in opposite directions
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