Exchange with the Environment
Bell Work:1/4/13
 What would happen to a factory if its
power were shut off or its supply of raw
materials never arrived?
 What would happen if the factory couldn’t
get rid of its garbage?
 Look at page 78!
Objectives
 Explain how materials move through
simple diffusion. (SPI 0707.1.5)
 Diffusion/Osmosis Demo, Lab, & Notes
 Table of Contents:
62. Diffusion and Osmosis Notes
Challenge Question?
 What cell organelle allows things to move
in and out of the cell?
 What things are allowed in and out of the
cell?
Discuss the questions with your Elbow
Partner.
Blowing Bubbles
• Soap bubbles have
properties, such as
flexibility, that are similar
to cell membranes.
• Components of soap film
and of cell membranes
move around freely
because they are made of
proteins and lipids (fats).
What is Diffusion?
 The movement of particles from regions
or areas of _________
concentration
high
(crowded) to areas of ________
low
concentration (less crowded) is called
____________.
diffusion
 Look at Figure 1 on pg. 78!
 The dye moved from an area of high
concentration and spread to the area of
low concentration.
 Ex: when oxygen diffuses into the cell
and carbon dioxide diffuses out.
Diffusion of Water
 Diffusion also happens with and between
living cells.
 The cells of organisms are surrounded by
and filled with fluids that are made mostly of
________.
water
 The diffusion of water through a
_____________
semipermeable (partially allows things
through) membrane is so important that it
has been given a special name__________.
osmosis
 Look at Figure 2 on pg. 79!
Question...Elbow Partner
 In diffusion and osmosis, why do the
particles move from areas that are
more crowded to areas that are less
crowded?
 For a cell to survive, the amount of
molecules need to be the same on both
sides of the cell membrane. If the cell
does not pump out all of its extras to
even things out, this could be very bad.
The cell can swell up and explode.
 Listen to this…
Moving Small Particles
 In a cell, the movement of particles across a cell
membrane _________
without the use of energy by the cell is
called __________
passive ___________.
transport
 During passive transport, particles move from an area
of _______
high concentration to an area of _______
low
concentration.
Diffusion & __________
Osmosis
 Examples:__________
 A process of transporting particles that requires the
cell to use energy is called ________
active ____________.
transport
 Active transport usually involves the movement of
particles from an area of _______
low concentration to an
area of _______
concentration.
high
 This happens a lot in neurons. The membrane
proteins are constantly pumping ions (atoms or
molecules that have a + or – electrical charge) in
and out to get the membrane of the neuron ready to
transmit electrical impulses.
Moving Large Particles
 The active transport by which a cell surrounds a large
particle, such as a large _________,
protein and encloses the
particle in a vesicle to bring the particle into the cell is
called _______________.
endocytosis
sacs formed from pieces of cell
 Vesicles are _____
membrane.
 Ex: when iron diffuses into the cell using active
transport because the iron molecules are too large.
wastes leave the
 When large particles, such as ________,
cell, the cell uses an active transport called
______________.
exocytosis
 During exocytosis, a vesicle forms around the large
particle, carries the particle to the cell membrane,
fuses with the cell membrane, and releases the
particle outside of the cell.
What do you know?
Describe how each of the following materials
would get through the cell membrane and
into a cell:
1. Pure water (osmosis)
2. Sugar entering a cell that already contains a
high concentration of particles (active transport)
3. Sugar entering a cell that has a low
concentration of particles (passive transport)
4. A protein (endocytosis)
Diffusion Lab
1. Fill beaker halfway with water. Teacher will add 20
drops of iodine to the water.
2. CAREFULLY place two heaping spoonfuls of
cornstarch into a plastic bag.
3. CAREFULLY add 25 ml of water in the bag of
cornstarch, keeping solution in the corner of the
bag. Seal the bag. Move the corner of the bag
between your fingers to mix the cornstarch and
water together.
4. Place the bag in the beaker and wait.
5. Check the bag and record your observations after
5, 10, and 15 minutes.
6. While waiting, fill out the lab paper, both front and
back. If you don’t finish, it will be homework.
Diffusion Lab Questions
1. The plastic bag is semipermeable to
which substance?
2. Why did the iodine enter the bag?
3. Why didn’t the starch enter the
beaker?
4. How is the plastic bag like the cell
membrane?
5. What is the definition of the word
“diffusion”?