Membrane electrical properties Flashcards
What is the RMP and what is its magnitude and purpose?
cells have a voltage difference across the PM known as the resting membrane potential (RMP). magnitude is between -20 mV and -100 mV depending on cell type. the RMP is needed for the Na+ dependent cotransport of glucose, amino acids, and other solutes into cells. RMP also needed for action potentials
Who is the scientist who pioneered electricity and proved electricity could be generated chemically?
Alessandro Volta
how strong is the electrical field strength of the RMP?
very strong. the plasma membrane is very thin and this creates a strong electrical field strength (voltage divided by distance)
what creates the RMP?
constant diffusion of potassium ions in both directions across the PM. K+ leak channels are always open and highly abundant in the PM
what are fixed intracellular anions
negatively charged molecules that are confined within the cell (the cannot cross the membrane). They are important because K+ ions leave behind fixed intracellular anions and can interact electrostatic ally with them across the thin membrane.
How unevenly distributed are the ions across the membrane?
not very. only a few K+ ions need to be unequal to set up the RMP, most of the cytoplasm is neutral. only about 1/100,000,000 of the total K+ ions are needed to create RMP
what conditions create the RMP?
- intracellular concentration of K+ is much night than extracellular concentration.
- K+ ions diffuse freely in both directions through leak channels
- Na+/K+ pumps are constantly pumping K+ into the cytosol, maintaining concentration at 140 mM
- extracellular K+ concentration is maintained at 5 mM by kidneys
Do you know how to use Nernst equation?
check in lecture 4 slide 14 and 16 and 19-23
remember 61.5(log10(k/k)). 61.5 only applies to atoms with one valence electron (K and Na)
what is the normal concentration of K+ ions across the membrane? Na+?
K+: 140 cytoplasmic and 5 extracellular.
Na+: 5-15 cytoplasmic and 145 extracellular
