Lecture 2/14

osmosis

osmosis

passive transport of water across the membrane

aquaporins

water channel proteins, allow water into the cell, enhances water transport via osmosis

the more aquaporins in the membrane….

the more water permeable the membrane is

membrane potential

the difference in voltage across the cell membrane

how is osmolarity measured

in osmoles (osm)

differences between intracellular and extracellular fluids

ionic and molecular composition differs, but osmolarity and osmotic pressure are the same

1 osm is equal to how many molecules in a liter

6.022 x 10^23, avogadro’s number

osmolality

molarity per mass of solvent (mmol/ kg)

isomotic

2 or more solutions have the same osomolarities

why are intra and extracellular fluids similar in osmolarity

if they are too different from each other the cells can lyse or dry out

what happens when NaCl dissolves in water

separates into Na+ and Cl-, increasing the osmolarity since there’s now two particles instead of one

what happens to osmolarity when MgCl2 dissolves in water

separates into Mg, Cl, and Cl; increasing osmolarity from one particle to three

what happens when glucose dissolves in water

glucose stays as glucose, does not increase osmolarity

osmotic pressure

tendency of a solution to gain/ lose water, a physical force that drives water from one location to another, only when there’s a difference in osmolarity

hydrostatic pressure

contraction/ reduction of volume pushes fluid from high to low pressure

how does water move in osmolarity

from low to high osmolarity; since there’s less water molecules in a solution with more stuff dissolved in it (concentration gradient)

how does water molecules move in pure water to a solution higher in osmolarity

only in one direction; to the higher osm solution since pure water has osmolarity of zero

osmoregulation

maintenance of a nearly constant osmotic pressure in plasma

high osmotic pressure

gains water (high osmolarity)

low osmotic pressure

loses water (low osmolarity)

hyperosmotic

solution has higher osmolarity than surrounding fluids

hyposomotic

solution has lower osmolarity to surrounding fluids

osmoconformers

internal osmolarity changes w/ environment

osmoregulators

internal osmolarity stays constant through expending energy

partial osmoregulator

can regulate osmolarity to a point then it conforms

what is the normal osmotic pressure for plasma in freshwater or saltwater fish

300 mOsm

if someone has alcohol poisoning you use

saline solution to hydrate since if you add pure water it causes cells to lyse

if a saltwater clam is thrown in freshwater what happens?

osmotic pressure goes from high to low, volume increases, extracellular fluid pressure decreases