Transport Across
Membranes
Transport Across
Membranes
Passive Transport
Examples of Passive Transport
Cells and Osmosis
Active Transport
Comparing Passive and Active Transport
Passive Transport
• Passive Transport: movement of
molecules across a membrane from an
area of high concentration to an area of
low concentration.
• Passive Transport does not require energy.
• Three types:
– Diffusion
– Osmosis
– Facilitated Diffusion
Examples of Passive Transport
1) Diffusion: the movement of any particle
from high to low concentration.
Glue this picture beneath your definition, Label the
areas of high and low concentration, then shade them
two different colors.
Examples of Passive Transport
2) Osmosis: the movement of water from
high to low concentration.
Glue this picture beneath your definition, Label
the areas of high and low concentration in
each picture, then shade them two different
colors.
Examples of Passive Transport
3) Facilitated Diffusion: movement of large molecules
from high to low through transport proteins.
Glue this picture beneath your definition, Label and shade
the areas of high and low concentration, and the transport
(carrier) proteins.
Cells and Osmosis
Hypotonic—water
moves into the cell
High Low.
Therefore cell
swells.
Isotonic—water
moves in and out of
cell because there is
no concentration
difference. Therefore
cell does not change.
Hypertonic—water
moves out of cell
High Low.
Therefore cell
shrivels.
Cells and Osmosis
• In animal cells, hypotonic conditions can
lead to lysis, cells bursting.
• In plant cells, hypotonic conditions provide
the water pressure needed to support the
cell wall.
• In plant and animal cells, hypertonic
conditions cause cells to shrivel (this is
why plants wilt when not watered).
Active Transport
• Active transport: movement of molecules from
an area of low concentration to an area of high
concentration.
• Active transport uses membrane proteins that
require energy (ATP).
Glue down the
picture, then label
and shade:
- Areas of high &
low concentration
- Membrane
proteins
- ATP
Active Transport
• Endocytosis: uses lots of energy to move
particles inside the cell.
• Exocytosis: uses lots of energy to move
particles outside the cell.
Comparing Active & Passive
Transport
• In the top portion of the flap, draw a Venn
diagram. Label one circle Active Transport and
the other Passive Transport.
• Place the words from the chart below into the
appropriate places on the Venn diagram.
Uses
energy
With a
gradient
Exocytosis
No energy
required
Osmosis
High  Low Low  High
Membrane
protein
Against a
gradient
Diffusion
Semipermeable
membrane
Movement
of particles
Facilitated
diffusion
Endocytosis
ATP
Comparing Active & Passive
Transport
High
Active Transport
Passive Transport
Low to High
High to Low
Uses Energy
No Energy
Low