HIGH
Concentration
LOW
Concentration
High Concentration
LOW Concentration
HIGH
Concentration
LOW
Concentration
Diffusion and osmosis
Types of Cellular Transport
How “stuff” gets into and outside of the cell membrane
 Passive Transport
cell does NOT USE ENERGY
1. Diffusion
2. Facilitated Diffusion
3. Osmosis
high
 Active Transport
cell USES ENERGY
1. Protein Pumps
2. Endocytosis
3. Exocytosis
Weeee!!!
low
This is
gonna be
hard
work!!
high
low
Bacon Frying…
What do you
smell?
Why do you smell
this?
Bacon Frying…
• Fat droplets are released into the
air by the steam coming off of the
bacon
• Causes the fat droplets (particles) to
collide and disperse.
In science terms…
• DIFFUSION IS OCCURING! 
The bacon fat droplets (particles)
diffuse from the area of high
concentration (directly above the
frying pan),
to areas of low concentration
(the room)
Continues until equilibrium is
reached
Particles equally distributed
throughout the space (room)
In the cell this is called
HOMEOSTASIS!!
Diffusion
• Diffusion - Defined as the movement of
particles from areas of high concentration to
areas of low concentration (down the
concentration gradient)
– Particles spread out
– Ex: Solute = perfume Solvent = the air
Low Solute
Concentration
High Solute
Concentration
Diffusion
What Can go through?
Oxygen
Carbon dioxide
What 3 things effect the rate of
diffusion? (how fast diffusion occurs)
Diffusion rate (how fast it occurs)
depends on:
1.
Size- smaller molecules move more easily
Concentration-
2.
high concentration = faster
spread
 Ex: The more bacon you have (=more fat droplets
released), the faster the smell will spread throughout the
room
Temperature-
3.
high temps speed up the process
Which will cause the smell to disperse faster?
Cold bacon in a frying pan and the stove is OFF
OR
Bacon in a frying pan and the stove in ON
What is a semi-permeable membrane?
• A membrane that allows
certain molecules to pass
through it by diffusion or
osmosis
• Think about a Ping-Pong
net..
• Which would pass
through?
Cell membranes are semi-permeable
• Water and some gases move through the
membrane easily, while larger molecules like
proteins and sugars do not.
• Cells must regulate- molecules move from
internal environment to external environment
(and vice versa) so that both environments
have equal concentrations.
– Animation: How Osmosis Works
Osmosis
• Diffusion that involves water.
• Movement of water across a semi-permeable
membrane
• WATER moves across the cell membrane
• Water moves across the cell membrane from areas
of low solute concentration to high solute
concentration
Osmosis
• Diffusion that involves water.
• Movement of water across a semi-permeable
membrane
• Water moves from areas of low solute
concentration to areas of high solute concentration
Why do your fingers “shrivel–up” when you are in the water?
Effects of Osmosis on Life
• Osmosis- diffusion of water through a
selectively permeable membrane.
• There are 3 types of solutions (=Tonicity)
1.) Isotonic
2.) Hypertonic
3.) Hypotonic
Solution
Cell
Solution
Cell
Isotonic Solution
• Solutions that contain the same concentration of
solutes as the cytoplasm are called isotonic (or
normal saline) solutions.
• There is no net movement of water either into or
out of the cell.
• Cells maintain their normal shape.
Isotonic Solution
Isotonic The concentration of solutes in the
external solution is equal to the concentration of
solutes inside the cell.
Result Water moves equally in both directions and
the cell remains same size! (Dynamic Equilibrium)
Hypertonic Solution
• A hypertonic solution is a solution that
contains more solutes than the cytoplasm of
the cell. (hyper)
• Has less water than the cell and
water moves out of the cell.
• The cells shrink.
Hypertonic Solution
Hypertonic: The solution has a higher concentration
of solutes and a lower concentration of water than
inside the cell. (High solute; Low water)
shrinks
Result: Water moves from inside the cell into the
solution: Cell shrinks (Plasmolysis/crenation)!
Hypotonic Solution
• A hypotonic solution contains less
solute (thus, more water) than the
cytoplasm of the cells.
• The water will move into the cells
resulting in the swelling and lysis
of the cells.
Hypotonic Solution
Hypotonic: The solution has a lower concentration
of solutes and a higher concentration of water than
inside the cell. (Low solute; High water)
Result: Water moves from the solution to inside
the cell): Cell Swells and bursts open (cytolysis)!
Let’s take a closer look!
https://www.youtube.com/watch?v=Ia
Z8MtF3C6M
What type of solution are these cells in?
A
B
C
What type of solution are these cells in?
A
Hypertonic
B
Isotonic
C
Hypotonic
Tonicity
Used to compare different solutions
Hypertonic- higher solute concentration relative
to another
*think hyperactive
Hypotonic- lower solute concentration relative to
another
*think hypothermia
Isotonic- equal solute concentrations between
two solutions
ENVIRONMENT
10% NaCL
90% H2O
CELL
10% NaCL
90% H2O
cell is
at _______________.
WhatThe
is the
direction
of water movement?
39
Cell in Isotonic Solution
ENVIRONMENT
10% NaCL
90% H2O
CELL
10% NaCL
90% H2O
equilibrium
cell is
at _______________.
WhatThe
is the
direction
of water movement?
NO NET
MOVEMENT
40
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement??
41
Cell in Hypotonic Solution
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
The cell is HYPERTONIC and the solution is HYPOTONIC
42
15% NaCL
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
43
Cell in Hypertonic Solution
15% NaCL
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
The cell is HYPOTONIC and the solution is HYPERTONIC
44
Cells in Solutions
45
Isotonic Solution
NO NET
MOVEMENT OF
H2O (equal amounts
entering & leaving)
Hypotonic
Solution
CYTOLYSIS
Hypertonic
Solution
PLASMOLYSIS
46
Cytolysis & Plasmolysis
Cytolysis
Plasmolysis
47
Osmosis in Red Blood Cells
Isotonic
Hypotonic
Hypertonic
48
What Happens to Blood Cells?
49