5.14 Passive transport is diffusion across a
membrane



Diffusion is the tendency for
particles to move from an
area of high concentration
to an area of low
concentration.
Concentration gradient is
the difference in
concentration on two sides
of a membrane
Passive transport – no
energy required by the cell
for this to happen

High
Low
O2, CO2
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html
5.15 Transport protein may facilitate
diffusion across membrane

Facilitated Diffusion


Passive transport


molecules that are too large
or that are charged move
down their concentration
gradient (high to low)
through protein channels or
carriers.
down its conc. gradient
Each molecule has a
particular protein channel
that it is designed to bind
with
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html
5.16 Osmosis is the diffusion of water
across a membrane


Water is one of the
most important
substances to move
across a membrane
Osmosis


Diffusion of water.
Movement from high to
low concentrations.
Passive transport

down its conc. gradient
http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html
5.16 Osmosis
Higher Concentration
of Water
Water molecules
Cell
membrane
Lower Concentration
of Water
Sugar molecules
http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf
5.17 Water balance between cells and their
surroundings is crucial to organisms.
Isotonic – the solution
outside the cell is equal
to the solution of the
cytoplasm. Iso means
the same.
Water will move equally in
both directions.
No net movement across
cell membrane.
Isotonic solution
5.17 Water balance between cells and their
surroundings is crucial to organisms.
Hypertonic – the solution outside
the bag is “hyper” meaning it is
above strength. Hyper means
high so the solution is high in
solute, low in water.
Water will move in both directions
but more will move to an area
of low concentration. This will
cause the cell to lose water.
Just like your potato in salt water.
Hypertonic solution
More solute = less water
5.17 Water balance between cells and their
surroundings is crucial to organisms.
Hypotonic – the solution
outside the bag is
“hypo” meaning below
strength. Hypo means
below so the solution is
low in solute and high
in water.
Water will move in both
directions but more will
move inside the cell.
Hypotonic solution
http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf