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Molecules to Medicine III > Cell Volume Regulation > Flashcards

Flashcards in Cell Volume Regulation Deck (12)

What is diffusion?

random, thermally-agitated movement of molecules
"random walk of diffusing particles"


What is osmosis?

spontaneous net movement of solvent molecules across selectively permeable membrane into a region of higher solute concentration


The movement of what molecules can change the volume of a cell



What 3 mechanisms have evolved to prevent cells from swelling and bursting?

1. Cell Wall: plants, fungi & bacteria (hydrostatic force metabolically expensive!!)
2. Animal Cell: allow solute molecules in ECF - water ACTIVITY is equal on both sides of plasma membrane (identity of solutes is unimportant -concentration matters)


What is the equation for osmotic pressure?

Pie (osmotic pressure) = RTdeltaC
R = gas constant
T - temp in kelvin
delta C = difference in concentration


What is tonicity?

measure of the osmotic pressure gradient of two solutions separated by a semipermeable membrane


What is osmolarity?

concentration of an osmotic solution
measure of solute concentration:
#osmoles of solute/L
aka osmotic concentration


What is molarity?

# of moles/ unit volume


What are equivalents?

having the same ability to combine


What is the reflection coefficient?

0 for THO, 1 for non-permiating solution
- measure of how well membrane "reflects" solute


How does permeability affect diffusion?

permeability of solutes can be slower that water-> reverse flow at first, until water catches up
- ex) dehydrated infant (blister grows- capillaries more permeable to NaCl- then water flows back in => equilibrium)

ex) new onset DM: hyperosmotic blood (blood capillaries less permiable -> as plasma glucose decreases -> glucose stranded in brain -> plasma is hypo osmotic -> water into brain! EDEMA/ pressure)


How do you convert between osmolarity and equivalents?

multiply osmolarity by valence

in uncharged solutes, mEq = mM