Chapter 4 –
The Cell In Action
What do you think?
1.
2.
3.
How do water, food, and wastes get into and
out of a cell
How do cells use food molecules?
How does one cell produce many cells?
4.1 – Exchange with the
Environment
Objectives:
1.
2.
3.
4.
Explain the process of diffusion
Describe how osmosis occurs
Compare passive transport with active
transport
Explain how large particles get into and out of
cells
Diffusion

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Diffusion is the movement of particles from an
area where their concentration is high to an area
where their concentration is low.
This movement can occur across cell
membranes or outside of cells.
Cells do not need to use any energy for diffusion
of particles to occur.
Osmosis



The diffusion of water through the cell
membrane is so important to life processes that
it has been given a special name – OSMOSIS
Water, like all matter, is made up of small
particles. Pure water has the highest possible
concentration of water particles.
To lower this concentration, mix the water with
something else (ex, food coloring, sugar, salt)
Moving Small Particles


Passive Transport – The diffusion of particles
through proteins in the cell membrane from
areas where the concentration of particles is
high to areas where the concentration of
particles is low
Active Transport – The movement of particles
through the proteins in the cell membrane
against the direction of diffusion; requires cells
to use energy
Moving Large Particles

Endocytosis – The process in which a cell
membrane surrounds a particle and encloses it
in a vesicle to bring it into the cell

Exocytosis – The process used to remove
large particles from a cell; during exocytosis,
a vesicle containing the particles fuses with
the cell membrane.