Ion Channels and Transport Flashcards
What are the driving forces in membrane transport?
chemical gradient, osmotic pressure, membrane potential and electrical gradient
What are the types of membrane transport?
active transport, passive transport, facilitated diffusion
What is active transport?
requires energy, usually from ATP hydrolysis
What is passive transport?
leak/ion channels
What is facilitated diffusion?
diffusion mediated by simple transporters (ex: glucose transport)
What is secondary active transport?
coupling energy from favorable reaction with unfavorable reaction
What are types of transporters that do facilitated diffusion?
uniporters
What types of transporters do secondary active
symporters/antiporters
What are voltage gated ion channels?
Na+, K+, Ca2+, Cl- channels activated by changes in membrane potential
What are water channels called?
aquaporins
What is an inward rectifier and what is its structure?
ion channel that is made to be favorable to let ions into the cell
two transmembrane domains and an ion selectivity filter, or pore loop
What are Katp channels and when are they active?
channels that let K+ out of cell
active when ATP is low and inactivated when ATP is high
What is the structure of Katp channels?
four pore units and four sulfonylurea receptors
What is the function of Katp channels in B-islet pancreatic cells?
in a high glucose state (eating/full), ATP increases which inhibits Katp channels and the cell depolarizes
depolarization stimulates opening of Ca2+ channels and insulin is released
What is the function of Katp channels in smooth muscle?
if ATP is low, Katp is activated and so Ca2+ channels remain closed so vasodilation
How do sulfonylureas treat diabetes?
they inhibit Katp channels so that insulin is released
How does minoxidil treat hypertension?
it inhibits Katp channels, leading to vasodilation
How do voltage gated K+ channels achieve potassium selectivity?
K+ has a water shell that has to be shed to enter selectivity pore
the pore contains carbonyls that micic conformation of water shell
How does the voltage sensing domain activate voltage gated channels?
made of positively charged AAs
at resting potential, inside of cell is negative and pulls domain in
when depolarized, inside is positive so the domain is repulsed and spring out, opening the pore
How do voltage gated Na+ channels achieve sodium selectivity?
form an egg shaped ring that is selective for partially hydrated Na+ ions
What are the different types of Ca2+ channels and where are they found?
L-type: heart, skeletal muscle
N, P/Q, R: neuronal
T-type: cardiac and neuronal pacemaker
How do local anesthetics work (lidocaine/procaine)?
block Na+ channels in nerves
What is a use dependent block?
for local anesthetics: the more stimulated the receptor is, the better the inhibitory function of the drug
What is fugu?
found in raw fish, a toxin that blocks nerve Na+ channels creating a tingling/numbing feeling
