Outcomes:
• Identify the factors which
influence the rate and
direction of diffusion.
• Identify how osmosis is
related to diffusion and
the value of osmosis to
living organisms.
• Examine the
mechanisms of active
transport by identifying
and explaining the two
processes.
• Compare the similarities
and differences
between active and
passive transport.
**Don’t have to write these
out**
Passive and
Active
Transport
Unit 2- Cell Structure and
Function
Cellular Transport
 Cellular
transport moves substances within
the cell and moves substances into and
out of the cell
 There are 2 types:
1.
2.
Passive Transport
Active Transport
Passive Transport
 These
types of transport do not require
energy
a)
b)
c)
Diffusion
Facilitated Diffusion
Osmosis
A) Diffusion
 Remember
from years before that
particles in solids, liquids, and gasses are in
constant random motion (Particle Theory
of Matter)
 Substances dissolved in water move
constantly in random motion
 The random motion of these particles
creates DIFFUSION
 The
amount of a substance in a certain
area is called CONCENTRATION
 Substances diffuse from an area of higher
concentration to an area of lower
concentration
 Watch the following video and draw the
diagram on the next page:

http://www.youtube.com/watch?v=Um6O
oN81rb4
Diagram of Diffusion
 Diffusion
occurs until there is an equal
concentration of particles in an area/cell
 The particles continue to move randomly,
but there is no overall change- this is
called DYNAMIC EQUILIBRIUM
Rate of Diffusion
3
main factors affect the rate that
diffusion occurs
1. Concentration

2.
Temperature

3.
When concentration is high, diffusion
happens quickly because there are more
particles to collide with each other
When temperature increases, the particles
collide more quickly
Pressure

When pressure increases, the particles
collide more quickly
B) Facilitated Diffusion
 While
water can diffuse readily across a
plasma membrane, most other
substances need help
 Happens through carrier and channel
proteins
 The
CHANNEL PROTEINS in the plasma
membrane of the cell are used to diffuse
ions and small molecules across the cell
membrane (draw the diagram below)
http://kentsimmons.uwinnipeg.ca/cm1504/Image132.gif
 CARRIER
PROTEINS are also used to move
substances across a cell membrane by
changing shape to help diffusion in a cell
(Draw the diagram)
http://www.biologyco
rner.com/resources/si
mpdiff.jpg
C) Osmosis
 The
diffusion of water across a selectively
permeable membrane is OSMOSIS
 Regulating the movement of water across
the plasma membrane is an important
factor in maintaining homeostasis
 (draw the next diagram)
http://www.biologycorner.com/resources/osmosis.jpg
 If
the concentration of solute is higher on
one side of the cell membrane, the water
will move towards the higher solute
concentration
 This diffusion happens until dynamic
equilibrium occurs
Isotonic Solution
 When
a cell is in a solution that has the
same concentration of water and solutes
is said to be in an ISOTONIC solution
 Water moves into and out of the cell at
the same rate and cells keep their normal
shape
Hypotonic Solution
 If
a cell is in a solution that has a lower
concentration of solute, the cell is said to
be in a HYPOTONIC solution
 There is more water outside of the cell
than inside the cell which causes water to
move into the cell
 The water moving into the cell creates
osmotic pressure
 In
an animal cell, the water may enter the
cell so much so that it bursts
 A plant cell will not burst if there is a high
osmotic pressure because the cell wall is
very rigid
Hypertonic Solution
 When
the concentration of the solute
outside of the cell is higher than inside
 Water moves outside the cell
 Animal cells may shrivel because of water
loss
 Plant cells wilt because the water vacuole
is empty
Draw the diagram:
http://4.bp.blogspot.com/yiAZAMJRq4s/Ta79K3vVk8I/AAAAAAAAACE/MhfD0z_ABi8/s1600/
hypo.jpg
Video Explanation
 http://www.youtube.com/watch?v=AYN
wynwaALo
Active Transport



This happens when substances have to move
from an area of lower concentration to an
area of higher concentration
This process makes sure that cells have the
proper amount of substances inside of them
These forms of cellular transport REQUIRE the
use of ENERGY by the cell
a)
b)
Pumps (carrier proteins)
Endocytosis/Exocytosis
A) Pumps (Carrier Proteins)
 Carrier
proteins can move substances
against a concentration gradient
 Some pumps move one type of
substance in one direction across the
plasma membrane
 Other pumps move two substances in
both directions across the plasma
membrane
Sodium Potassium Pump
 This
is a common type of pump
 moves 3 sodium ions out of the cell
 moves 2 potassium ions into the cell
 ATP (a form of energy) breaks down into
ADP to do this
 Video demonstration

http://www.youtube.com/watch?v=Q73uJ
8WlY_E
http://4.bp.blogspot.com/_207DNIaLgc/TOaSu8u3q7I/AAAAAAAAAV4/9QLnFO82wQA/s1600/07_16Sodium
PotassiumPump.jpg
B) Endocytosis & Exocytosis
 Particles
that are too large to travel
through the plasma membrane leave or
enter the cell differently
Endocytosis
 ENDOCYTOSIS
is when a cell surrounds
something outside of the cell
 The cell membrane pinches off and
leaves the substance inside the cell
 The substance is now in a vesicle to travel
throughout the cell
Exocytosis
 Is
when substances leave the cell by
vesicles joining the plasma membrane to
expel the substance
http://www.kscience.co.uk/as/module1/pictures/endoexo.jpg