ICPP - Resting Membrane Potential Flashcards
What is the membrane potential?
The magnitude of an electrical charge that exists across a plasma membrane.
What are membrane potentials measured in?
Millivolts (mV)
True or false - some animal cells have negative membrane potentials at rest?
True - they all do.
Which type of animal cell has the smallest negative membrane potential?
Erythrocytes
Which cell has the most negative resting membrane potential?
Skeletal muscle cell
How is cell membrane potential measured?
Use a fine glass pipette (microelectrode) which can penetrate cell membrane. Tip is less than 1 micrometer and filled with a conducting solution (KCl). Connect a voltmeter to it and measure potential.
What are the two “minimum essentials” required for a membrane potential to be established?
ASYMMETRIC DISTRIBUTION of ions across the plasma membrane and SELECTIVE ION CHANNELS in the plasma membrane.
Give three properties of ion channels.
SELECTIVITY (for one/a few ion species), GATING (pore can open or close by conformational change), RAPID ION FLOW (always down gradient).
True or false - when the chemical and electrical gradients for K+ are equal and opposite, there will be no movement of K+ and a negative charge across the membrane?
True!
Given the intracellular and extracellular concentrations of K+, what can you calculate using the Nernst equation?
The membrane potential at which K+ will be in equilibrium.
True or false - a very large amount of K+ must move across the membrane to set up the voltage?
False - less than 1% of ions.
Why do erythrocytes have such a low resting membrane potential?
They have virtually no selectivity for K+.
Why does cardiac muscle have a resting membrane potential that is less negative than Ek (K+ equilibrium)?
Not perfectly selective for K+.
