Transcript Diffusion & Osmosis

Read silently to find the answers to
these questions:
How do different molecules enter
and exit cells?
2) What is a lipid bilayer?
3) What is the main function of the
cell wall?
4) How does diffusion occur?
5) What is the difference between
diffusion and osmosis?
1)
Work with your Partner
 1)
Share your answers with your
partner.
 2)
Write the best answer in your
notebook
 3)
Share the best answer with the
class
Diffusion & Osmosis
Diffusion
The movement of molecules
from an area in which they
are highly concentrated to an
area in which they are less
concentrated.
Diffusion
Osmosis
 The
diffusion of water across a
selectively permeable membrane.
 Osmosis
is a type of Passive
Transport.
 Osmosis
requires NO ENERGY.
Osmosis



Hypertonic- a
solution that causes a
cell to shrink because
of Osmosis.
Hypotonic- a solution
that causes a cell to
swell because of
Osmosis.
Isotonic- a solution
that causes no change
in the size of the cell
Osmosis

In this picture a red
blood cell is put in a
glass of distilled
water. 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.
Selectively Permeable
A
membrane that allows only certain
materials to cross it
 Materials pass through pores in the
membrane
Summary
Diffusion is the movement of molecules
from an area of higher concentration to an
area of lesser concentration.
 Osmosis is the movement of water thru
a semi permeable membrane.
 Active transport requires energy.
(molecules move from an area of lesser to
higher concentration)
 Passive transport needs NO ENERGY!
(molecules move from an area of higher to
lesser concentration).

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
 A balance, or EQUILIBRIUM, must be
maintained.
