Download Diffusion & Osmosis

Diffusion & Osmosis
Define Diffusion
Diffusion
 The
movement of molecules from a
area in which they are highly
concentrated to a area in which they
are less concentrated.
Draw a diagram of an
example of diffusion we
saw in class.
Draw a diagram of an example of
diffusion we saw in class.
See an animation of
diffusion here:
http://lewis.eeb.uconn.ed
u/lewishome/applets/Diffu
sion/diffusion.html
Define osmosis
Osmosis
 The
diffusion of water across a
selectively permeable membrane.
Define osmosis

Water moves from a high
concentration of water (less salt or
sugar dissolved in it) to a low
concentration of water (more salt or
sugar dissolved in it). This means
that water would cross a selectively
permeable membrane from a dilute
solution (less dissolved in it) to a
concentrated solution (more
dissolved in it).
http://www.usd.edu/~bgoodman/Osmos.htm
Define osmosis
http://www.usd.edu/~bgoodman/Osmos.htm
Define osmosis

In this picture a red blood
cell is put in a glass of
distilled water (all water
with no salt or sugar in
it). Because there is a
higher concentration of
water outside the cell,
water enters the cell by
OSMOSIS. In this case
too much water enters and
the cell swells to the point
of bursting open. In the
end pieces of cell
membrane are left in the
water.
http://www.usd.edu/~bgoodman/Osmos.htm
See an animation of
osmosis here:
http://lewis.eeb.uconn.ed
u/lewishome/applets/Osm
osis/osmosis.html
Define selectively
permeable membrane
Selectively Permeable Membrane
A
membrane that allows only certain
materials to cross it
 Materials pass through pores in the
membrane
For more information on
diffusion & osmosis, click
here:
http://edtech.clas.pdx.edu/osmosis_
tutorial/default.html
Why are osmosis &
diffusion important?
Why are osmosis & diffusion
important?
All living things have certain requirements
they must satisfy in order to remain alive
– maintain homeostasis
 These include exchanging gases (usually
CO2 and O2), taking in water, minerals,
and food, and eliminating wastes.
 These tasks happen at the cellular level.
 Molecules move through the cell
membrane by diffusion

Why are osmosis & diffusion
important?
 All
living things have certain
requirements they must satisfy in
order to remain alive. These include
exchanging gases (usually CO2 and
O2), taking in water, minerals, and
food, and eliminating wastes. These
tasks ultimately occur at the cellular
level, and require that molecules
move through the membrane that
surrounds the cell.
Why are osmosis & diffusion
important?
 This
membrane is a complex
structure that is responsible for
separating the contents of the cell
from its surroundings, for controlling
the movement of materials into and
out of the cell, and for interacting
with the environment surrounding
the cell.
Osmosis
 If
environment is:
– Hypertonic:

MORE SOLUTES outside cell


MORE WATER IN CELL
over time, cell loses water and shrinks


“Iso-” means environment “=” cell
No change in cell volume

LESS SOLUTES outside cell
– Isotonic:
– Hypotonic:
LESS WATER IN CELL, more solutes in
cell.
 over time, cell gains water
HYPO—HIPPO

OSMOSIS
HYPERTONIC
ISOTONIC HYPOTONIC
OSMOSIS
HYPERTONIC
ISOTONIC HYPOTONIC
Osmosis
Shriveled RBCs
Normal RBCs
Swollen RBCs
Hypertonic Solution
Isotonic Solution
Net movement of
water out of cells
Equal movement of water
into and out of cells
Hypotonic Solution
Net movement of
water into cells