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Dissolved substances and gas can move by diffusion. It is the
mixing of two products using the natural movement of
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
This is because diffusion happens in a High to low concentration gradient
Cells can use diffusion to get products they need
·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

Slide 3

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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
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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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 RESPIRATIO
Also sugar and ions which can pass through N This is particularly
membranes, can be moved by active useful for plants
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
prevent it from collapsing
Rib muscles
Can raise and
lower the rib cage The rib cage
to help breathing It is strong bone that
protects the contents
of the thorax (upper
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
·Thin (small diffusion distance)
There are two examples in the body
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 exchange.
network of capillaries supplying They are also located close to blood
blood. capillaries supplying blood…read more

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