Functions of Channels and Transporters Flashcards
How do ion channels differ from aqueous pores?
- show ion selectivity
- NOT continuously open (can open and close)
Where are ion channels found?
- ALL animal cells
- plant cells
- microorganisms
What is the location and function of K+ leak channels?
- PM of most animal cells
- maintenance of RESTING membrane potential
What gives the membrane high selective permeability?
lipids in the membrane
A small flow of ions carries sufficient charge to cause a large change in the ____ _____.
membrane potential
Where are the ions that give rise to the membrane potential?
thin (<1 nm) surface layer close to the membrane
How are ions held on the surface layer near the membrane?
by their electrical attraction to their oppositely charged counterparts (counterions) on the other side of the membrane
When is the membrane potential equal to zero?
when there is an exact balance of charges on each side of the membrane so that each positive ion is balanced by a negative counterion
What causes a nonzero membrane potential?
when few positive ions cross the membrane, leaving their negative counterions behind
(leak channels)
Electrochemical gradients are measured based on what is (inside/outside) the cell.
inside
The Na+/K+ pump helps maintain _____ _____ across the cell membrane.
osmotic balance
The Na+ concentration inside the cell is (low/high).
low
Which ion serves as the balancing role in the Na+/K+ pump?
K+
Is K+ actively pumped (into/out of) the cell by the Na+/K+ ATPase?
into
What is located on the PM and allows K+ to flow freely in and out of the cell?
K+ leak channels
For every molecule of of ATP hydrolyzed inside the cell, the pumps move __ Na+ (in/out) and __ K+ (in/out).
3 out
2 in
The equilibrium condition where there is no voltage gradient across the PM which causes K+ to flow out of cell (since there’s a high concentration of K+ inside the cell) and as it does, it leaves behind an unbalanced negative charge creating a membrane potential and once that potential reaches a certain point, K+ will no longer move out of the cell.
resting membrane potential
How can the resting membrane potential be calculate?
Nernst Equation
What do we need to know for the Nernst equation?
internal and external ion concentrations
Which part of the neuron receive signals?
dendrites
Where does the axon conduct signals from and to?
away from cell body and to the terminal branches of the axon
When an action potential reaches the nerve terminal in a presynaptic cell, it stimulates the terminal to release its
neurotransmitter
Which type of channel is involved in hearing?
mechanically gated channels
stress-activated
Hereditary disease of ion channels and carrier proteins that involves mutations in the CFTR gene which is a chloride channel
cystic fibrosis
Ion channel blocker that involves sodium channels
tetrodotoxin
Ion channel blocker that involves voltage gated sodium channels
Saxitoxin
Ion channel blocker that blocks sodium ion channels
Lidocaine and novocaine anesthetics
Ion channel blocker that blocks potassium channels
Iberiotoxin (eastern indian scorpion)
Ion channel blocker that blocks potassium channels (brown spider)
Heteropodatoxin
What is tetrodoxin produced by?
puffer fish
What type of drugs target molecules of the excitatory synapse?
Antiepileptic drugs
Superfamily of integral membrane proteins responsible for ATP-powered translocation of molecules such as sugars, amino acids, lipids, ions, polysaccharides, peptides, proteins, toxins, drugs, antibiotics, xenobiotics and other metabolites.
ATP-binding cassette (ABC) transporters
What are the 4 domains of ABC transporters?
2 hydrophobic
2 ATP-binding
When is the interface between ATP-binding domains open?
when ATP is hydrolyzed
When is the interface between ATP-binding domains closed?
when ATP is bound
Clinical importance of ABC transporters: (3)
- cause of drug resistance which develops in many human cancers
- mutation in ABC chloride carrier = cause of CF
- cause of drug resistance which frequently develops in malaria parasite
Type of mechanism that gets proteins across a lipid bilayer membrane (inside –> outside) which are unable to pass through the bilayer directly themselves
exocytosis of secretory vesicles
What are the 3 possible fates for transmembrane receptor proteins following endocytosis?
- recycling
- transcytosis
- degradation
What is the location and function of voltage-gated Na+ channels?
PM of nerve cell axon
generation of action potentials
What is the location and function of voltage-gated K+ channels?
PM of nerve cell axon
return membrane to resting potential after initiation of action potential
What is the location and function of voltage-gated Ca2+ channels?
PM of nerve terminal
stimulation of NT release
What causes opening and closing of voltage gates channels?
changes in membrane potential
Where are ATP-binding domains located?
cytosol
purpose of sequestration of endocytosed proteins
recycle receptors
Why is there antibiotic resistance?
mutations occurred in transporters repsonibsle for bringing antibiotics from outside to inside of bacterial cell (if it’s not inside, it won’t kill the cell bc it won’t have access to cellular machinery that it targets and tries to inhibit)
