Transporters and Channels 2 Flashcards
1
Q
Transporters in facilitated diffusion
A
- hydrophobic, polar molecules can enter cell through specialised carrier proteins
- do not require energy
- can show saturation kinetics
2
Q
Transporters in active transport
A
- hydrophilic, polar molecules can enter the cell through specialised carrier proteins
- requires energy
- is capable of moving molecules against concentration gradient
- can show saturation kinetics for carrier
3
Q
What are P-glycoprotein transporters
A
- multidrug transmembrane transporters (ATP dependent)
- responsible for multi-drug resistance
4
Q
Functions of P-glycoprotein transporters
A
- Liver: transporting drugs into bile for elimination
- Kidneys: pumping drugs into urine for excretion
- Placenta: transporting drugs into maternal blood
- Intestines: transporting drugs into intestinal lumen, reducing drug absorption into blood
- Brain capillaries: pumping drugs back into blood, limiting distribution in brain
5
Q
Transport through symport
A
- solute A transport into cell is coupled with transport of solute B into cell
- CG going from area of lesser concentration to area of greater concentration, powered by movement of solute B going from high->low
6
Q
Transport through antiport
A
solute A is transported against CG, powered by transporting solute B the opposite way (out)
7
Q
Cis-effects of transporters
A
- saturability: substrate molecules compete for transporter binding-sites
- stereospecificity: certain stereoisomers are better fit to binding site
8
Q
Trans-effects of transporters
A
- exchange diffusion: trans-substrate accelerates exchange
- counter transport: trans-acceleration by a different substrate (hetero-exchange)
9
Q
Competitive inhibition
A
- increase substrate Km
- unchanged Vmax
10
Q
Non-competitive inhibition
A
- decreased Vmax
- unchanged Km
11
Q
How do Loop diuretics work
A
by blocking transport to sodium pump, leading to hypokalemia
12
Q
How do thiazide diuretics work
A
- by blocking sodium chloride co-transporter, preventing sodium from entering pump and creating a gradient
- lowering Na concentration in epithelial cells increases activity in sodium potassium antiporter
13
Q
Describe the mechanism of open channel blockers
A
- e.g. cocaine
- enter pore of ion channel or interact with intermediate stages involved in channel opening
- reduces frequency of APs occurring, results in a reduction in signal transmission
14
Q
Structure of cys-loop receptors
A
- pentamers
- either homo-oligomers or hetero-oliogmers
- subunit composition affects pharmacology
15
Q
Structure of ionotropic glutamate receptors
A
- tetramers
- either homo-oligomers or hetero-oligomers
- gated by glutamate and mediate excitatory neurotransmission in CNS
