Bellringer
• List the two things that make up the cell
membrane.
• What does it mean to be selectively
permeable?
From the lab, Order of the
items…
• Biggest: ?
• Smallest: ?
• Where do the pores fit in?
Sizes of Molecules…
•
•
•
•
•
Water (H2O)
Iodine (I2K)
Glucose (C6H12O6)
Food Coloring (~450 atoms)
Starch (~1000 atoms)
So…how big
are the pores of
the membrane?
Make an
estimate (with
an explanation)
on the back
side of your
questions!!!
Fluid Mosaic Model
• http://www.susanahalpine.com/anim/Life/m
emb.htm
• http://www.youtube.com/watch?v=ULR79T
iUj80
Role of the membrane?
• Selective permeability
Roles of the membrane proteins
• Move stuff across the membrane that can’t
get across on its own
• Recognition – like nametags
• Receptors – trigger cellular responses
• Enzymes
How does the membrane regulate
movement of molecules?
• It’s structure dictates!!
Cell Membrane
• Cell Membrane Animation
• Made of phospholipids and proteins
• Molecules move into and out of a cell through the
cell membrane
• The cell membrane is selectively permeable
• How certain molecules move through the cell is
called cell transport
– Passive Transport
– Active Transport
Questions
• What happens when you spray air
freshener or perfume?
• What happens when you put food
coloring in water?
• THIS IS DIFFUSION!!!! Diffusion is
also one way things are transported
across the cell membrane
What is concentration?
• Amount of solute in a certain amount of
solvent…think about kool-aid…
– Solvent – what does the dissolving (liquid)
– Solute – what is dissolved in the solvent
– Which is more concentrated?
Passive Transport
• Particles move from high
concentration to low concentration
• Does NOT require extra cell energy
• Includes simple diffusion, osmosis,
facilitated diffusion
SIMPLE DIFFUSION
• Movement of molecules from areas of high
concentration to areas of low concentration
• Does not require energy (PASSIVE)
– Because molecules are in constant, random,
motion!
• Will diffuse until reaches equilibrium (equal
concentrations)
• Dynamic equilibrium (still moving!)
Diffusion
Dynamic
Equilibrium
For lab…
• To the tube,
add:
–Glucose
solution
–Starch
• To the beaker,
add:
–Water
–Iodine
Make a hypothesis….
• Will the glucose move? Which way? Why
or why not?
• Will the iodine move? Which way? Why
or why not?
• Will the starch move? Which way? Why or
why not?
Flea Diffusion Analogy
Flea Diffusion Analogy
Flea Diffusion Analogy
Dynamic Equilibrium
Simple Diffusion in Cells
Diffusion Animation
Diffusion Across a Membrane
PROBLEM BREAK
OSMOSIS
• The diffusion of water across a
membrane from an area of high
concentration to low concentration
• No energy required (PASSIVE
TRANSPORT)
• Occurs until reaches DYNAMIC
EQUILIBRIUM
– Equal concentrations on both sides of
the membrane
Tonicity of solutions
• Used to compare the relative concentrations
• Hypertonic
– solution with a higher concentration of solute
– So lower water concentration
• Hypotonic
– solution with a lower concentration of solute
– So higher water concentration
• Isotonic
– solutions with equal concentrations of solute
• Water diffuses from hypotonic solutions to
hypertonic solutions!
http://www.linkpublishing.com/videotransport.htm#Brownian_Movement
Cells in Hypertonic Solution
• Water moves out of
the cell
• Cell shrivels
HYPERTONIC
Low
Hi
Hypotonic Solution
• Water moves into the
cell
• Cell swells
– Animal cell – can burst
– Plant cell – builds up
pressure on cell wall,
but rigid cell wall
keeps it from bursting
HYPOTONIC
Hi
Lo
Isotonic Solution
• Water moves in and
out of the cell
• Cell stays the same
size
• Dynamic Equilibrium
ISOTONIC
http://www.tvdsb.on.ca/westmin/science/sb
i3a1/Cells/Osmosis.htm
• What happens to slugs in salt?
• Dead bodies in the river?
FRAYER MODEL BREAK!
Draw example
define
Passive
transport
Explain your
example
Does it require
energy?
Examples
Starter
• Consider the following • Considering this
information:
information, devise a
rule that describes
– Water, oxygen, and
CO2 all readily move
what CAN and
across a membrane
CANNOT pass
– Glucose, proteins and
through the membrane
small ions (like Na+ or
via SIMPLE
Cl-) cannot pass on
DIFFUSION
their own
Pumping Water
• Some organisms have
vacuoles that pump
out excess water that
enters the cell
• Too much water in the
cell = vacuole works
hard pumping out
water!
•
http://www.linkpublishing.com/videotransport.htm#Brownian_Movement
FACILITATED DIFFUSION
• Particles move from high concentration to
low concentration
• No energy needed (PASSIVE)
• Cells use proteins to “help”
– Transport Proteins
– Channel proteins
http://www.stolaf.edu/people/giannini/biological%20anamations.html
FRAYER MODEL BREAK!
Draw example
define
Facilitated
Diffusion
Explain your
example
Does it require
energy?
REVIEW PASSIVE
TRANSPORT
Active Transport
• Particles move from low
concentration to high concentration
(against the concentration gradient)
• DOES REQUIRE ENERGY!!
• Requires transport proteins
• Includes pumps, endocytosis,
exocytosis, etc.
The sodium-potassium pump
•
•
•
•
Active Transport = requires energy!
Sodium is pumped out
Potassium is pumped in
Animation
Active transport
Examples: Pumping
Na+ (sodium ions) out
and K+ (potassium
ions) in against
strong concentration
gradients.
Called Na+-K+ Pump
Sodium-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped
out; creates a membrane potential
Pumps
• Some animals use salt pumps to maintain a
constant concentration of salt in their bodies
• This requires energy! ACTIVE
TRANSPORT!
Pom-Pom Potential
• Modeling passive and active transport along
a cell membrane in a NERVE CELL
• What do nerves do?
• How do they do it?
Questions
• How did this activity model passive
transport?
• How did this activity model active
transport?
• Why do the membranes “work” to keep the
charges on either side of the membrane
“balanced”?
FRAYER MODEL BREAK!
Draw example
define
Active
transport
Explain your
example
Does it require
energy?
Examples
VENN DIAGRAM TIME: MUWAHAHAHAHA
ACTIVE
TRANSPORT
FACILITATED
DIFFUSION
MOVING THE BIG STUFF…
•Large
substances
leave the
cell
•Vesicle
fuses with
cell
membrane
and dumps
contents
Exocytosis
The opposite of endocytosis is exocytosis. Large
molecules that are manufactured in the cell are
released through the cell membrane.
Inside Cell
Cell environment
Moving the “Big Stuff”
Exocytosis
- moving
things
out.
Molecules are moved out of the cell by vesicles that fuse
with the plasma membrane.
This is how many hormones are secreted and how nerve
cells communicate with one another.
Exocytosis
Exocytic
vesicle
immediately
after fusion
with plasma
membrane.
Ponder for a moment…
• How does exocytosis fit into PROTEIN
SYNTHESIS????
•Large
substances
enter the
cell
•Cell
membrane
forms a
“pit” and
wraps
around
substance
•Cell
membrane
pinches off
– forms a
vesicle
Cell Signaling
• Signaling activity
• Modeling Nerves…
Go to picture 
http://learn.genetics.utah.edu/content/addiction/drugs/mouse.html
Journal
• Draw a diagram of what we just did and…
• Identify the types of transport going on, as
completely as possible (there are TWO you
should identify!).
• Provide justification for your selection.