BIOLOGY: OSMOSIS

diffusion

The random movement of molecules

so that they spread out evenly into

the available space.

Dynamic equilibrium

An even distribution with continuous

movement of molecules, but no

overall concentration change.

Simple Diffusion

A substance will diffuse from where it is more concentrated to where it is less concentrated; from an area of high concentration to low concentration, until there

is equal concentration. (Down a concentration gradient.)

passive transport

No work is done; no energy is expended; a spontaneous process...

polar molecule

Water is a

positive(H)/negative(O)

Because of the structure of an H2O

molecule, it has a slight _____________ charge on

one end and a slight ______________ charge on

the other end.

cohesion

Due to its hydrogen bonds, water likes to cling

to ITSELF

adhere

Because of its polarity (slightly charged ends),

it will cling to anything else with a

charge.

hydrogen bonds

Water molecules bond to each other

using

weaker

hydrogen bonds are _______________ than covalent bonds

exert a string force

if there a lot of hydrogen bonds together they can __________________

solution

Completely homogeneous mixture of two or

more substances (solvent + solute).

solvent

The dissolving agent; must have charges to

dissolve (water is a universal solvent)

solute

The dissolved substance (ex. Sugar or salt)

osmosis

The diffusion of WATER across a semipermeable

membrane.

free water

Water molecules that are not

"stuck" to the solute (sugar).

cannot cross

The larger sugar molecules (solute) ___________ ____________ the semipermeable membrane.

motion

Water molecules are in constant

can

Free water _____________ pass through the

semipermeable membrane.

less

There is ___ free water on the right side of

the U-tube.

higher to lower

Water moves from an area of ___________ to

______________ free water concentration.

net direction

The overall direction of movement of

the free water.

The free water is moving from more

free water/less solute to where there

is less free water/more solute.

(BUT... water will actually pass in

smaller amounts in the reverse, too,

through random collisions.)

Tonicty

The ability of a solution to cause a cell to gain or lose water.

-Isotonic, hypotonic, and hypertonic environments

same

Iso means

isotonic

Equal concentration of solutes (and free

water) inside and outside of the cell.

-

isotonic enviornment

There will be no net movement of water

across the plasma membrane of an

animal cell immersed in an _______________ ______________

-Water flows across the membrane, but at

the same rate in both directions.

-The volume of the cell is stable.

less

Hypo means

hypotonic

Less solute on the outside of the cell, greater

concentration of solutes inside. or more dree water on the outside than on the inside

-Water will enter the cell faster than it leaves (moving to where there is less free water).

-The cell will lyse (burst) like an overfull water balloon.

more

Hyper means

hypertonic

More solutes outside the cell/less free water on the outside

-The cell will lose its water to its environment

(moves to where there is less free water), will

shrivel and die.

-Example: If the salinity of a lake increase and the

lake water becomes hypertonic to the animals'

cells, the animals can die.

Selectivity permeable membrane

allows certain things to pass: free water CAN, but solute CANNOT