Bio 120 Unit 4

What are the three major “compartments” in which water is found in the body

Cells, interstitial fluid, and blood

Osmolarity def

number of osmotically active particles per liter of solution

tonicity def

measure of how a solution will cause water to move into or out of a cell

osmosis def

movement of water molecules across a membrane in response to a solute concentration gradient

what is the most important non-penetrating solute

NaCl

what happens to cell placed in hypotonic solution ([ ] lower outside cell)

water will move into cell

what happens to cell placed in hypertonic solution ([ ] greater outside cell)

water will move outside cell

what is an osmoconformer

organism’s osmolarity matches its environment

what is an osmoregulator

organisms input energy to alter osmotic levels so that it can maintain a nearly constant osmolarity, regardless of environment

what are aquaporins

membrane channels that allow water to move through

how do osmoregulators in seawater behave

challenge: salt gain, water loss
solution: active salt excretion, little urine produced

how do osmoregulators in a terrestrial environment behave

reduce water loss from body’s surface (wax surface to prevent sweating), reduce water loss from urine

how do osmoregulators in freshwater behave

challenge: water gain, salt loss

solution: lots of dilute urine, active uptake of salts