Section 7-3 cont.
Cellular Transport
Passive Transport
Does not use energy
1. Diffusion



Movement of particles from an area of higher
concentration to an area of lower concentration.
Dynamic Equilibrium - Tries to reach an equal
concentration inside and outside the membrane
2. Osmosis – Diffusion of Water
3. Facilitated Diffusion

Passive transport of materials across the
plasma membrane with the aid of transport
proteins.



Move from high to low concentration
Transport proteins provide openings for particles
to pass through
Move molecules that may not be soluble in lipids
or may be too large to pass through the pores in
the cell membrane.
Suppose that a unicellular protist lives in a solution that is
5% saltwater. Dr. Stapleton moves the protist to another
saltwater solution to study the rate of osmosis. Which of
these solutions would cause the protist to lose mass at the
greatest rate?
25%
25%
25%
25%
1.
2.
3.
4.
3% saltwater
solution
4% saltwater
solution
5% saltwater
solution
6% saltwater
solution
1
2
3
4
Three Types of Solutions
 1.
Isotonic –
concentrations
are the same
inside the cell as
they are outside
the cell
Three Types of Solution Cont.
 2.
Hypotonic –
concentration of
substances is
lower outside
the cell than the
concentration of
substances
inside the cell.
Hypotonic cont.
The cell swells and may burst in animal
cells
 As a plant cell swells, the cell wall
supports the cell so it won’t burst, but it
will become more firm.

Three Types of Solution Cont.

3. Hypertonic –
the concentration
of substances
outside the cell is
higher than the
concentration of
substances inside
the cell.
Hypertonic cont.

Animal cells shrivel

Plant cells lose water mainly from the
central vacuole. The cell membrane and
cytoplasm shrink away form the cell wall.
This causes plants to wilt.
A scientist places a cell in a solution, and over time the
cell gains mass and swells.
What is the most likely explanation for the cell’s gain in
mass?
1.
2.
3.
4.
The solution is
hypertonic to the cell.
The solution is
hypotonic to the cell.
The solution and the
cell have equal
concentrations of
solutes.
The solution and the
cell have equal
concentrations of
water.
25%
1
25%
25%
2
3
25%
4
Active Transport
Requires energy from the cell
 Moves from low to high concentration
