quiz #1 - osmolarity

iso-osmotic

if the solution (same as the ECF) has the SAME osmolarity as the ICF (intracellular fluid of the red blood cell)

hyper-osmotic

if the solution (same as the ECF) is HIGHER than the ICF

hypo-osmotic

if the solution (same as the ECF) is LOWER than the ICF

how to determine the tonicity of a solution

determine osmolarity (iso, hyper, hypo - osmotic), determine if the solute is penetrating or non-penetrating, determine whether a concentration gradient of non-penetrating particles between ECF and ICF exists or not, and

penetrating molecules

solute particles (ions or molecules) that can cross plasma membrane and enter the cell ex. Urea

non-penetrating solutes

solute particles that cannot cross the plasma membrane and enter the cell ex. NaCl

hypo-tonic

if the cell has higher concentration of non-penetrating solutes than the solution, there will be net movement of water into the cell - cells swell and possibly burst

hyper-tonic

if the cell has lower concentration of non-penetrating solutes than the solution, there will be net movement of water out of the cell - cells shrink or crenate

osmosis

diffusion of water across a membrane from a region of lower concentration of non-penetrating solutes to a region of higher concentration of non-penetrating solutes

osmolarity

concentration of all solute particles in a solution (ECF or cytoplasm of cell)

tonicity

defined by the nature of the solute that either prevents or promotes osmosis from occurring to a cell

osmotic pressure

the net movement of water from osmosis results in increased hydrostatic pressure in the more concentrated solution which opposes net water movement and when pressure is high enough to prevent movement its called…

osmolarity always compares solutions to solutions ex. solution a is hyperosmotic to solution b while…

tonicity compares solution and a cell ex. solution A is hypertonic to cells

tonicity cannot be calculated but...

osmolarity has units of omoles/L and can be calculated

tonicity tells you shape or cell volume while...

osmolarity does not

why does net water movement stop at some point

when the water moves from two different compartments, the hydrostatic pressure increases in one of the compartments and this increases the water in the other compartment to make them equal

water activity

is the relative availability of water to freely move within a solution

hydrostatic pressure increases…

water activity