Download Passive transport PP

Do Now 11/7
OBJECTIVES:
1. define osmosis, diffusion, facilitated
diffusion, passive transport, concentration gradient,
equilibrium, and dynamic equilibrium.
2. predict the flow of water and solute molecules across
semipermeable membranes, and describe how these processes
affect living cells.
TASK:
1.
HW check 5.11-13; 2. The cells of plant seeds store oils in
the form of droplets enclosed by membranes. These
membranes are very different from the cell membrane even
though they are made of the same phospholipids.
Draw a simple model for a membrane around an oil droplet,
and briefly explain why this arrangement is more stable than
bilayer.
hydrophilic
Since the oil is
hydrophobic,
this
membrane
has only ONE
LAYER. Polar
head groups
on the
outside,
hydrophobic
tails in the oil
hydrophobic
A Quick Demonstration…
How is this picture of outer space similar to the demonstration?
Diffusion!
Hot
Water
Cold
Water
Passive Transport
• Passive transport is the movement of
molecules from areas of high
concentration to areas of lower
concentration. It happens spontaneously
(spontaneous = requires no addition of
energy)
It’s the same for stardust and
molecules!
• Diffusion: The movement
of particles from an area of
high concentration to lower
concentration.
• It’s caused by the random
motion of particles (aka
thermal energy)
• When the concentration of
particles becomes equal in
all parts of the
environment, that’s called
equilibrium.
Equilibrium
• When the concentration of solute is equal
throughout a solution.
Dynamic Equilibrium
• Dynamic equilibrium refers to a state
where the overall conditions don’t change,
but individual parts keep moving
• Example: 5 molecules move in, 5
molecules move out, still at equilibrium.
Diffusion: A type of passive
transport
• Passive transport is the movement of
matter into or out of a cell WITHOUT the
use of energy by the cell.
• Diffusion across the cell membrane is how
small molecules get into and out of cells.
Concentration Gradient
• A concentration gradient is a difference in
concentration across a space.
• Going “down” the concentration gradient
means moving from an area of high
concentration to low
High Concentration
Low Concentration
“down” the gradient 
How your cells get O2 and get rid of
CO2
Diffusion: why • Since they
flatworms are flat ! have no
respiratory
system,
planarians like
this have a
flattened body
plan to allow for
fast diffusion of
oxygen and
carbon dioxide
to all their cells.
Do Now 11/18
• OBJECTIVE: Complete previous.
• TASK:
• 2. For each word pair in parentheses, select
the correct word.
– In diffusion, (solute / solvent) molecules move (up /
down) their concentration gradients, from areas of
(higher / lower) concentration to areas of (higher /
lower) concentration.
Osmosis: The diffusion of water
across a semi-permeable
membrane
Things always
move from
areas of higher
concentration to
lower
concentration
spontaneously
(passively)
Effects of Osmosis can be serious
for a cell!
Hypotonic
Hypertonic
Water out
Of cell
Isotonic
No net change
Water into cell
SOLUTE SUCKS!
• Water moves to where there is more
solute.
Hypo Hypo Hippo
How cells cope
Osmosis & Plants
Plant Cells & Osmosis
Plasmolysis
Hypotonic environment
Causes turgor pressure.
Plant is healthy.
Hypertonic environment
Causes wilting.
Plant is unhealthy.
Plasmolysis
One Last Time
Facilitated Diffusion
• Facilitated diffusion is like regular diffusion
in that substances are moving from high
concentration to low without the use of cell
energy.
• The difference is the solute molecules
can’t get through the membrane alone,
and travel through proteins instead.
Facilitated Diffusion
Membrane
Proteins
Solutes too big
Or too polar
To diffuse normally
Wrap Up / Key Ideas
• Diffusion: The movement of solute molecules down a
concentration gradient. Small molecules (e.g. H2O,
O2, CO2) cross the cell membrane via diffusion
• Osmosis: The diffusion of water across a semipermeable membrane.
• Facilitated Diffusion: The diffusion of large and/or
polar molecules across the cell membrane through
proteins.
• Passive Transport: Movement of material into or out
of a cell without the use of energy by the cell.
• Concentration gradient: A difference in solute
concentration across a space.
DO Now 11/17
• Reverse osmosis is a process used to
desalinate salt water to make it drinkable.
– How might this process work? Sketch a design that
uses a semi-permeable membrane to purify water.
– Is this process passive or active? How do you
know?
You Need Energy to Go Up a
Concentration Gradient!
Fresh water out
Salt water at high pressure
Selective membrane prevents large
solutes and ions from passing
through.
They become MORE concentrated
Definition:
Passive Transport
Type 1
Type 2
Type 3
DIFFUSION
Definition: Key Term:
Solute
molecules
move from
an area of
high
concentration to an
area of low
conc.
Powered
by the
random
motion of
molecules.
Equilibrium
OSMOSIS
Hypertonic:
Solute conc. Bigr
outside. H2O out
Isotonic:
Solute conc. =
Inside & out.
No net H2O
change.
Hypotonic:
Solute conc. Lower outside.
H2O in. Hypo-Hippo
The process of
substances passing
through the cell
membrane WITHOUT
ANY INPUT OF
ENERGY BY THE
CELL.
FACILITATED
DIFFUSION
Definition:
Definition:
Diffusion of
water from
an area of
high H2O
conc. (low
solute
conc.) to
low (high
solute
conc.)
Required for
Ions
(charged
molecules)
And
Large
Molecules
Cell uses
carrier
proteins in
membrane to
allow the
diffusion of
molecules
that can’t
pass through
membrane
alone.
Read All About it!
• Section 5-1 “Diffusion” pp. 95-96
• SR #1, p. 100.