Slides in this set
· Diffusion is the gradual movement of particles from places
where there are lots of them to places where there are
fewer of them.
· DIFFUSION is the passive movement of particles from an
area of HIGH CONCENTRATION to and area of LOW
Diffusion happens in both liquids and gases that's because the
particles in these substances are free to move about randomly.
The simplest type is when different gases diffuse through each
other. This is what happening when the smell of perfume diffuses
through a room.
The bigger the difference in concentration the faster the diffusion
· Cell membranes:
Cell membranes are clever because they hold the
cell together BUT they let stuff in and out as well.
Substances can move in and out of cells by
diffusion and osmosis. Only very small molecules
can diffuses through cell membranes though
things like glucose, amino acids, water and
Big molecules like starch and proteins can't fit
through the membrane.…read more
· Cell membranes:
Just like with diffusion in air, particles flow through the cell
membrane from where there's a high concentration to
where there's a low concentration.
They're only moving about randomly, so they go both
ways but if there are a lot more particles on one side of
the membrane there is a net (overall) movement from that
The rate of diffusion depends on 3 main things:
· Distance substances diffuse more quickly when they haven't
got far to move.
· Concentration difference substances diffuse faster if there is a
big difference in concentration. If there are lots more particles
on one side, there are more to move across.
· Surface area the more surface there is available for molecules
to move across the faster they can get from one side to the…read more
· OSMOSIS is the movement of water molecules
across a partially permeable membrane from a
region of high water concentration to an area of
low water concentration.
A partially permeable membrane is just one with very
small holes in it so very small molecules (like water)
can pass through them and bigger molecules (like
The water molecules eventually pass both ways
through the membrane during osmosis. This happens
because water molecules move about randomly all
the time.…read more
Because there are more molecules on one side,
there's a steady net flow of water into the region
with fewer water molecules.
This means the strong sugar solution gets more
dilute. The water acts like it's trying to even up
the concentration either side of the membrane.
Osmosis is a type of diffusion passive movement
of water particles from an area of high water
concentration to an area of low concentration.…read more