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Leaves are broad which means that there is a large surface area to
absorb sunlight. They are also thin which means that carbon dioxide
and water vapour only have to travel a short distance to get to the
cells for PHOTOSYNTHESIS.
· In the SPONGE MESOPHYLL LAYER, there are air spaces to allow
gases such as carbon dioxide (CO2) and oxygen (O2) to diffuse in
easily. This means that there is a large surface are for the gas
exchange ( big internal surface area to volume ratio).
· Leaves contain a lot of CHLOROPHYLL which absorbs sunlight
during photosynthesis. Chlorophyll are found in CHLOROPLASTS
which are found in the PALISADE LAYER. Light can pass through to
the palisade layer because the UPPER EPIDERMIS is transparent.
· The lower surface of the leaf is full of
holes called the STOMATA. It lets CO2 and
O2 diffuse in and out. They allow water
to escape which is transpiration.
· Leaves have a network of VEINS which
delivers WATER and OTHER NUTRIENTS
to every part of the leaf and takes away food
from the leaf. They support the leaf structure.…read more

Slide 3

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LEAF PALISADE CELLS are designed for
PHOTOSYNTHESIS as they have a lot of
CHLOROPLASTS. They have a tall shape
which means that A LOT OF SURFACE
AREA is exposed to sunlight and it can
absorb C02 from the air.
· There is a good chance of SUNLIGHT
hitting a chloroplast in the leaf before
reaching the BOTTOM OF THE CELL
because of its tall shape.…read more

Slide 4

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Diffusion in leaves happens when carbon
dioxide enters the leaf and oxygen exits the
leaf through the stomata.
· DIFFUSION is the passive movement of a
region of high concentration to a region of
low concentration.…read more

Slide 5

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OSMOSIS is the movement of higher
concentration of water to a lower concentration
of water.
· A living plant cell has a MEMBRANE just inside
its cell wall. This membrane is PARTIALLY
PERMEABLE so only small molecules such as
water can pass through, other molecules such as
glucose and salt molecules cannot pass through
because their particles are too big.
· FLACCID is when a plant doesn't get as much
water as it needs so it looks floppy.
· TURGID is when a plant gets too much water
(turgor pressure) that it becomes big, hard and
rigid.
· PLASMOLYSED is when there is less water
pressure against the cell wall which makes the…read more

Slide 6

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An animal cell doesn't have a cell wall so it will; swell
and burst when too much water enters through
(called LYSIS) and shrink causing CRENATION when
too much water leaves the plant.
· EXAMPLE: If a blood cell is placed in salt water or
pure water, it loses or gains water by osmosis. IT hasn'
t got any cell wall for support so it shrinks which is
crenation or it bursts which is lysis.…read more

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