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TRANSPORTER SEBAGAI TARGET AKSI OBATPengantar: Tinjauan Membran Sel
15 October 2012
The Cell Membrane
Cell Membrane:
At Very High Magnification & in color
Membrane Structure
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellMembranes.html
Protein membran• Integral: embedded within bilayer
• Peripheral: reside outside hydrophobic region of lipids
Protein membran…. cont.
Text pg 80
How to get other molecules across membranes??
Mekanisme transport membran
I. Passive Transport
• Difusi- perpindahan substansi (molekul) dengan turunnya gradien konsentrasi dari daerah dengan konsentrasi molekul tinggi ke daerah konsentrasi rendah
• Difusi terfasilitasi- tipe passive transport yg menggunakan bantuan transport proteins/ carrier proteins
• II. Active Transport– Menggunakan bantuan ATP
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
• Transport proteins Transports molecules or ions across biological membranes
• 3 types of transport proteins:1. uniport 2. symport 3. antiport
UNIPORT SYMPORT ANTIPORT
Uniport Transport Protein
extracellularfluid
intracellularfluid
Carries a single solute across the membrane
Ex: Transporter glukosa GLUT1; Transporter GABA; Transporter kolin
Symport Transport Protein
• Translocate 2 different solutes simultaneously in same direction.
intracellularfluid
extracellularfluid
Ex: simport glucose Na+; simport Na+/Cl-
Antiport Transport Protein EXCHANGER (Countertransporter)
• Exchanges 2 solutes by transporting them in opposite directions.
intracellularfluid
extracellularfluid
Ex: ADP/ATP Exchanger; diffusion anion antiporter in red blood cells
Membrane Transport MechanismsII. Active Transport
• Active transport- The movement of molecules (small or large) across the plasma membrane & against concentration gradient in which energy (ATP, PEP, light energy, electron transport) is required.
• Examples: ATP-powered Ion pump
1. Sodium (Na) - Potassium (K) Pump Na+/K+ ATPase2. Pump Ca2+3. K+/H+ ATPase di sel parietal lambung
Sodium-Potassium Pump• The mechanism that uses energy (active
transport) released from splitting ATP to transport Sodium (Na+) out of and Potassium (K+) into cells.
The Na+ - K+ pump cycle
HOW THE MECHANISM??
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
Glucose Transporter:How it works..(on the other scheme)
• glucose binds to outside of transporter (exterior side with higher glucose conc.)
• glucose binding causes a conform. change in protein
• glucose drops off inside cell
• protein reassumes 1st configuration
How carrier proteins change conformation
The ligand bindingsite is exposed onthe upper membranesurface
The folding pattern flips to a different position
The ligand bindingsite is now exposed onthe lower membranesurface
The carrier isnow ready totransport anothermolecule
Without the ligand bound, conformation returns to the first state
Facilitated diffusion anion antiporter in red blood cells (RBC)
• Multipass protein that binds to spectrin• Exchanges Cl- for HCO3
-
• Important for transporting CO2 to the lungs
Facilitated diffusion anion antiporter in red blood cells
• When the bicarbonate diffusion gradient is reversed, the process reverses
Why HCO3- for CO2?Why antiport Cl-?
TRANSPORTER SEBAGAI TARGET AKSI OBAT
Hidrophilic Agent Transporter (Uniport)1
SIMPORT/Co-transporter Contoh obat: - Tiazid : simport Na+/Cl- pada
Tubulus distal - Furosemid: simport Na+/K+/2Cl-
pada Loop Henle
2
THE NEPHRONGlomerulus Bowman’s capsule Proximal convoluted tubule
Loop of Henle: descending, ascending Distal convoluted tubule collect. tubule
Mekanisme aksi Thiazide
1
Mekanisme Omeprazole
2