Transcript Diffusion & Osmosis

Diffusion & Osmosis
(Passive Transport)
Passive Transport
 When
materials are moved without
using the cell’s energy
 Osmosis and diffusion are 2 types of
passive transport.
Define Diffusion
The movement of molecules from a
area in which they are highly
concentrated to a area in which they
are less concentrated.
example of diffusion
See an animation of
diffusion here:
http://highered.mcgrawhill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_diffusion
_works.html
Define osmosis
 The
diffusion of WATER across a
selectively permeable membrane.
Selective Permeability
 A membrane that allows only certain
materials to cross it
 Materials pass through pores in the
membrane
Define osmosis
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.
See an animation of
osmosis here:
http://highered.mcgrawhill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_osmosis
_works.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 (stable
environment)
 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

Endocytosis and Exocytosis are
ACTIVE TRANSPORT
Active transport means that the cell needs
energy to move the material through the
cell.
 Materials that are too large to move
through the membrane are moved by
endocytosis or exocytosis
 Active transport is necessary because
sometimes cells need to move materials
from lesser concentrations to greater
concentrations. (Kidneys use this process
to remove excess salt)

Endocytosis
 Endocytosis
cell.
 Exocytosis
cell.
moves materials into the
Exocytosis
move materials out of the
Endocytosis and Exocytosis are
forms of Active Transport.
Endocytosis
Exocytosis
Exocytosis and Exocytosis
 http://bcs.whfreeman.com/thelifewir
e8e/content/cat_040/0504003.html
 http://www.youtube.com/watch?v=l
gHJUkGPBqs
 http://www.youtube.com/watch?v=D
uDmvlbpjHQ