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DIFFUSION
Dissolved substances and gas can move by diffusion. It
is the mixing of two products using the natural
movement of particles
An example of diffusion is spraying
perfume
All of the particles are in a highly
concentrated area, but over time they
diffuse into areas of lower
concentration, so you can smell it
further away
High to low concentration
Cells can use diffusion to get products they need gradient
·This cell has oxygen inside and
surrounding it
·When this oxygen is used up in
respiration by the cell
·The cell needs more, so it uses
diffusion to absorb more from the
surrounding area through its
membrane…read more

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OSMOSIS
Is a special type of diffusion
It only occurs in water or soluble solutions through a partially permeable membrane
Eventually the water
moves so much that
the level on the more
concentrated side of
the membrane rises,
while the other side
falls
Osmosis is the movement from a Low to a high concentrated solution
Osmosis is important to plants
· They gain water by osmosis through
their roots.
·Water moves into plant cells by
osmosis, making them turgid or stiff so
they that able to hold the plant upright.…read more

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ACTIVE TRANSPORT
Its when substances are absorbed against the concentration gradient
It is similar to trying to push a ball up the hill, against
gravity This movement
requires energy.
Active transport
requires energy
because it takes
place in the opposite
direction to which
normal diffusion
would occur
The energy is accumulated from RESPIRATI
This is
Also sugar and ions which can pass
through membranes, can be moved by
ON
particularly
useful for plants
active transport and the kidneys…read more

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HOW IS THE BODY SPECIALISED FOR EXCHANGING
MATERIALS? The trachea
(windpipe)
It has rings of
cartilage that
Rib muscles
prevent it from
Can raise and
collapsing
lower the rib cage
to help breathing
The rib cage
It is strong bone that
protects the
contents of the
thorax (upper body)
The millions of
alveoli provide
a huge surface The diaphragm
area, meaning Muscular `sheet'
the lungs can dividing the thorax
absorb more and the abdomen
oxygen…read more

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Four properties are good for gas exchanges:
·Large surface area
·Rich blood supply
·Moist
·Thin (small diffusion distance)
There are two examples in the body
VILLI ALVEOLI
Villi line the walls of the small In the lungs they are millions of
intestine. They have a massive alveoli, they provide a massive
surface area and extensive surface area for gasous
network of capillaries exchange. They are also located
supplying blood. close to blood capillaries
supplying blood…read more

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