Session 3 - What is a membrane potential? Flashcards
What is a membrane potential?
Membrane potential: the potential difference across a cell’s plasma membrane
How do you measure membrane potential?
- Micropipette/ microelectrode, connected to voltmeter, penetrates the cell membrane
When membrane potential is measured, what is it expressed as?
- Membrane potentials expressed as voltage of inside of a cell relative to the outside
What is animal cell range of membrane potential?
Animal cell range: -20 to -90 mV
What is skeletal and cardiac muscle range of membrane potential?
Skeletal & cardiac muscle: -80 to -90 mV
What is nerve cells membrane potential?
Nerve cells: -50 to 75 mV
How is a membrane potential set up?
Membrane potentials are set up because the membrane is selectively permeable to different ions due to transmembranous channel proteins.
Give three characteristics of ion channels
Monspecificity
Gating
A high rate of ion flow
What is monospecificity of ion channels?
Channels that let through one (or a few) ion species
What is gating of an ion channel?
Channel can bbe open or closed by a conformational change in the protein molecule
What is special about the high rate of ion flow through an ion channel?
It is always down the electrochemical gradient for the ion
Depending on which channels are open…
The resting membrane can be selectively permeable to certain ion species
What is the intracellular and extracellular ion conc of Na+
Na+
Intracellular ~10mM
Extra cellular -145mM
What is the intracellular and extracellular ion conc of K+
Intracellular - 160 mM
Extracellular - 4.5 mM
What is the intracellular and extracelular ion conc of Cl-?
Intracellular - 3mM
Extracellular - 114mM
What is A- in cell ion terminology?
Represents anions other than Cl-, including phosphate, amino acids and charged groups on proteins
What is the intracellular concentration of A-? What is the extracellular?
167 mM intracellular
40mM extracellular