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Heny EkowatiPHARMACY DEPARTMENT

MEDICINE AND HEALTH SCIENCES FACULTY

UNIVERSITY OF JENDERAL SOEDIRMAN

2013


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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 CO2 to 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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TERIMA KASIH

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