Download Cell Membranes Osmosis and Diffusion

Osmosis and Diffusion
Methods of Transport Across
Membranes
1. Diffusion
2. Osmosis
Methods of Transport Across
Membranes
1. Diffusion –movement of any material or
particles from high concentration to low
concentration
2. Osmosis - movement of water from high
concentration to low concentration
across a semi-permeable membrane
Diffusion
• Movement of molecules from an area of
high concentration to an area of lower
concentration.
Diffusion
concentrated,
[High]
[Low]
diffuse, low energy molecules
Osmosis
• Osmosis is the movement of WATER across a
semi-permeable membrane
• At first the concentration of solute is very high on
the left.
• But over time, the water moves across the semipermeable membrane and dilutes the particles.
water
membrane
6
sugar solution
There are as many water molecules on the right as there are
on the left but many of them are attached to sugar molecules
and are not free to move.
7
Because there are more freely moving water molecules on
the left, more diffuse through the pores of the membrane from
left to right. From high concentration to low concentration.
• Hypotonic Solution/Dilute - One solution
has a low concentration of sugar/salt than
another.
• Hypertonic Solution/Concentrated - one
solution has a high concentration of
sugar/salt than another.
Osmosis
4
Osmosis
water or
dilute solution
concentrated
solution
level falls
level rises
membrane
More water passes from
dilute to concentrated ...
...until concentrations
become equal
Osmosis in Animal Cells
PLANT CELLS
Hypotonic
Solution
Turgor Pressure builds in the cell
and causes osmosis to stop
because of the rigid cell wall.
Hypertonic
Solution
Plants will wilt when cells
lose water through osmosis.
Plant and Animal Cells put into
various solutions