“Materials move across
the cell’s membranes”
Section 2.3
Do Now!! 
What is the purpose of the cell membrane?
What would happen if we didn’t have cell
membranes?
What goes in and out of our cells?
Objectives
To explain the different functions of the
macromolecules in the plasma
membrane.
To understand the process of diffusion.
To compare and contrast active and
passive transport.
The Cell Membrane
Called a “Fluid Mosaic
Model”
Proteins and other
components embedded
like a mosaic
 http://www.youtube.com/watch?v=
Qqsf_UJcfBc
Membrane Components
 Phospholipids:
Give the general structure of the membrane
Composed of:
Hydrophilic head
Hydrophobic tails
Please draw a phospholipid!
Draw a phospholipid and label its parts!
Membrane Components
Proteins:
 Allow bigger substances to
pass through
 Provide structure:
Ex: Microtubules and
microfilaments (cytoskeleton)
Membrane Components
Cholesterol: helps maintain structure of
phospholipids
prevents the tails from sticking together
Membrane Components
Carbohydrates: receptors that send and receive
signals from other cells
Attached to proteins (glycoprotein) and
phospholipids (glycolipid)
Explain what’s happening…
Types of Transport across a
cell membrane
Passive Transport
Active Transport
Vesicular Transport
Passive Transport
Does NOT require energy
Molecules go from an area of high
concentration to an area of low
concentration
“Go with the flow”
3 Types of Passive Transport
1. Simple diffusion
2. Facilitated diffusion
3. Osmosis
Simple diffusion?
 Movement of particles from area where there are
many to area where there are fewer
 Moves from high to low concentration
Simple diffusion (cont.)?
 Molecules move from high concentration to low
concentration to create DYNAMIC EQUILIBRIUM
 Concentrations are the same in all areas
Affected By…
 Heat- higher temp increases rate
 State of Matter
Solid- slow
Liquid- faster
Gas- fastest
 Size and Concentration
Bigger= slower
More concentration = faster
Do Now!! 
Explain what happens when you put a
sugar cube in your tea in regards to
diffusion.
Objectives
Explain facilitated diffusion
Define solute, solvent and solution
Identify different types of solutions
Facilitated Diffusion
 Certain molecules need a “helper” or
“facilitator” to allow them to cross the
membrane when they are too big.
Osmosis
o The flow of WATER from a high
concentration to a low concentration
Solution
o A mixture in which you cannot
separate the components (ex:
iced tea)
o solute: the substance being
dissolved
o Ex: iced tea powder
o solvent: The substance doing
the dissolving
o Ex: water
Isotonic Solutions
 Same amount of solute inside the membrane as
there is outside.
 Cell in this solution: NOTHING 
Plant Cell
Blood Cell
HYPERtonic Solutions
More solute, less water on outside of the
membrane
Cell in this solution: shrinks/shrivels 
Plant Cell
Blood Cell
HYPOtonic Solutions
Less solute, more water on outside of membrane
Effect: cell swells or bursts! /
Plant Cell
Blood Cell
Identify the type of solution!
Cell in ________
Solution
H2O
H 2O
Cell in ________
Solution
H 2O
H 2O
Cell in ________
Solution
H 2O
H 2O
Answer key!
Cell in hypotonic
Solution
H2O
H 2O
Cell in isotonic
Solution
H 2O
H 2O
Cell in hypertonic
Solution
H 2O
H 2O
Let’s try another…
 For the following examples:
Which way is the water moving?
What kind of solution is it?
What is going to happen to the cells?
A.
B.
C.
2% Salt
3% Salt
12% Salt
9% Salt
28% Salt
28% Salt
Real life osmosis situations
A salt water fish is put into a
freshwater aquarium.
What type of solution is the
freshwater?
What is going to happen to
the cells of the fish?
Real life osmosis examples
A patient is given an IV, which contains the
perfect balance of saline.
What type of solution is
in the IV?
What is going to happen
to the cells of the
human?
Real life osmosis examples
Your garden is infested with slugs so
you go around pouring salt on them
What type of
solution is this salt?
What is going to
happen to the cells
of the slug? (don’t
do this to the poor
slugs )
Do Now!! 
 What is diffusion?
 What do you think “passive” transport is?
 What do you think the difference is between
passive and active transport?
Objectives
 To define active transport
 To compare and contrast endocytosis and
exocytosis
 To complete a gummy bear osmosis lab
activity
Active Transport
 When molecules move from a low
concentration to a high concentration and
must use ENERGY (ATP).
 Example- Sodium Potassium Pump
 http://highered.mcgrawhill.com/sites/0072495855/student_view0/chap
ter2/animation__how_the_sodium_potassium_
pump_works.html
Vesicular Transport
 Sometimes things enter and exit the cell by
forming vesicles. For example…
 Endocytosis: When cells absorb molecules by
engulfing them. (like pacman)
Endocytosis
Pinocytosis: when the substance being engulfed
is a LIQUID.
Phagocytosis: when the substance being
engulfed is a SOLID.
Vesicular Transport
 Exocytosis: When cells expel unwanted materials
from vesicles.
Vesicular Transport
 http://highered.mcgraw-hill.com/olc/dl/120068/bio02.swf
Let’s review osmosis…
 What is osmosis??
 What are the three types of solutions??
 Identify the following:
A.
B.
2% Salt
3% Salt
C.
12% Salt
9% Salt
28% Salt
18% Salt