transporter farmol2014
TRANSCRIPT
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Heny EkowatiPHARMACY DEPARTMENT
MEDICINE AND HEALTH SCIENCES FACULTY
UNIVERSITY OF JENDERAL SOEDIRMAN
SEPTEMBER 2014
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Some carrier types facilitate
diffusion, others use energyto pump molecules against
Their gradient. They must
bind the solute to initiate
a conformational change
Membrane protein transporter types
Channels facilitate diffusion
through an aqueous porewhen a conformational
change opens a gate
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The membrane lipid barrier:
Passive diffusion through the lipid bilayer
Concentration gradient up, diffusion up Molecule lipid solubility up, diffusion up
Molecular size up, diffusion down
Molecule electrically charged, diffusion blocked
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Specialized membrane proteins transport
molecules across membranes
Simple diffusion
Species of molecule limited
by membrane physics
Rate is slow and linearlyrelated to concentration
gradient
Membrane transport
Overall not limited by size,charge, or hydrophilia
Is highly selective for
specific needed molecules
Rate is fast and not linear
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Carrier types
Uniporter- transports only one molecule species
Symporter- coupled transport of 2 differentmolecular species in the same direction
Antiporter- coupled transport of 2 different
molecular species in the opposite direction
Symporters & antiporters are usually pumps
Some types transport more than one molecule of a
species/cycle
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The glucose uniporter transports glucose
across membranes
Ligand (glucose) binding flips the transporter to a
different conformation (changes shape)
The new conformation releases glucose on the
other side of the membrane
Release allows it to flip back to repeat the cycle
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Band 3 facilitated diffusion anion
antiporter in red blood cells
Multipass protein that binds to spectrin Exchanges Cl- for HCO3-
Important for transporting CO2to the lungs
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Band 3 facilitated diffusion anion
antiporter in red blood cells
When the bicarbonate diffusion gradient is
reversed, the process reverses
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Band 3 function in RBCs
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Primary active transport example:
The Na+- K+antiporter pump
Pumps 3 Na+ ions out of cell & 2 K+ ions in Maintains Na+& K+ cell membrane gradients
Each cycle uses one ATP, 100 cycles/sec
Uses energy of most cells, for neurons
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The Na+- K+pump cycle
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Secondary active transport example:
The sodium-glucose symporter pump
Gradients from primary pumps power secondaryactive transport
Different types, can be antiporters or symporters
Pictured, the Na+gradient powers conformationalchange
Glucose is pumped in against its gradient
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Retrieval of GI tract glucose by enterocytes
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THE NEPHRON
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THE NEPHRON
Glomerulus Bowmans capsule prox. conv. tubule Loop (ansa) of
Henle:descend. limb, arcus, ascend. limb dist. conv. tubule collect. tubule
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Simport: Na+/Cl-
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Simport Na+/K+2Cl-
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Uniport GABA
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Na+/K+ ATPase
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H+/K+-ATPase
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