Flashcards in Membrane Potential Deck (88)
What is a P-type ATPase?
An ion channel that hydrolysed ATP to move the ion, forming an phosphoenzyme intermediate
What is approximately the resting membrane potential of a cell?
What is mainly responsible for maintaining a resting membrane potential of -70mV?
The diffusion of K+ ions out of the cell
How would you define a symporter ion channel?
An ion channel that transports 2 different types of ion in the same direction
By which mechanism does a secondary active transporter function?
A secondary active transporter transports its ion(s) using the energy of an electrochemical gradient, as opposed to the hydrolysation of ATP in primary active transport
What 2 factors does the Na+ H+ Exchanger regulate in a cell? Explain how.
The Na+ H+ Exchanger regulates pH, via the removal of H+ ions from within the cell.
It's also regulates cell volume, by pumping Na+ ions into the cell - water follows these ions into the cell down the concentration gradient that the Na+ ion movement creates.
Although indirectly, what ion transporter plays a major role in the maintenance of a cells pH?
The Na+ K+ ATPase pump
What 3 osmotically 'active' ions play a key role in the movement of water through a cell? How does water react to their movement?
Na+, K+, and Cl-
In general,Mayer follows these ions in/out of the cell
Do animal cells have a positive or negative resting membrane potential?
Define the membrane potential.
The magnitude of electrical charge across a plasma membrane
State the 2 main factors that are crucial in maintaining a membrane potential
Asymmetric distribution of ions across a membrane
Are K+ ion concentrations higher inside or outside the cell?
Are cations positively or negatively charged?
Positively charged ions
What type of molecules is the lipid bilayer of the plasma membrane permeable to?
Small uncharged molecules
What equation is used to work out the chemical,gradient of an ion?
RTln( (X)out / (X)in )
R = gas constant
T = temperature in Kelvin
At equilibrium, what are the chemical and electrical gradient in regards to one another?
What is the Nernst Equation used to calculate?
The resting membrane potential at which a specific ion will be in equilibrium (an ions concentration and electrical gradient will be in equilibrium)
Which ion in particular plays the most prominent role in maintaining the resting membrane potential?
Will an ion prefer to move down its chemical or electrical gradient first?
An ion will move down its chemical gradient before its electrical gradient
What are the equilibrium potentials for Na, K, Cl, and Ca?
Na = 70mv
K = -95mv
Cl = -96mv
Ca = 122mv
What is depolarisation?
Depolarisation is where the membrane potential of the cell decreases, causing the interior of the cell to become more positive
What is the Golman-Hodgkin-Katz equation used to work out?
It is used to work out the membrane potential of a cell based on its permeability to Na, K, and Cl
What is hyperpolarisation?
An increase in the size of the membrane potential, where the interior of the cell becomes more negative
How many acetylcholine molecules must bind a nicotinic acetylcholine receptor for it to open? What will this then allow through?
2 acetylcholine molecules must bind the receptor for it to open - it will let through cations (namely Na and K)
Concerning ion channels, how many ways of 'gating' are there? What are they?
- ligand gated
- voltage gated
- mechanical gated
List 2 inhibitory neurotransmitters. How do they act?
Glycine and GABA - they act by opening anion ligand-gated channels which allow K and Cl to enter the cell - this causes hyperpolarisation, meaning the cell will not be able to fire an action potential
In the Goldman-Hodgkin-Katz equation, which ion has an opposite orientation to the other?
How does opening a nicotinic acetylcholine receptor affect the membrane potential of a cell?
It lets in cations, particularly Na and K, moving the membrane potential towards 0mv (an intermediate between the membrane potentials of Na and K)
List 3 excitatory neurotransmitters. What do they cause?
Acetylcholine, glutamate, and dopamine - they cause depolarisation of the cell via influx of ions such as Na or Ca