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All animals and plants are made of cells. Animal cells and plant cells have
features in common, such as a nucleus, cytoplasm, cell membrane, mitochondria
and ribosomes. Plant cells also have a cell wall, and often have chloroplasts and
a permanent vacuole. Note that cells may be specialised to carry out a particular
Dissolved substances pass into and out of cells by diffusion. Water passes into
and out of cells by osmosis.…read more

Slide 3

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Dissolved substances have to pass through the cell membrane to
get into or out of a cell. Diffusion is one of the processes that
allows this to happen.
Diffusion occurs when particles spread. They move from a region
where they are in high concentration to a region where they are
in low concentration. Diffusion happens when the particles are
free to move. This is true in gases and for particles dissolved in
solutions. Particles diffuse down a concentration gradient, from
an area of high concentration to an area of low concentration.
This is how the smell of cooking travels around the house from
the kitchen.
In the lungs, the blood will continue to take in oxygen from the
alveolar air spaces provided the concentration of oxygen there is
greater than in the blood. Oxygen diffuses across the alveolar
walls into the blood, and the circulation takes the oxygen-rich
blood away.…read more

Slide 4

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Water can move across cell membranes
because of osmosis. For osmosis to happen
you need:
two solutions with different concentrations
a partially permeable membrane to separate
Partially permeable membranes let some
substances pass through them, but not others…read more

Slide 5

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Osmosis is the movement of water from a less concentrated
solution to a more concentrated solution through a partially
permeable membrane.
Eventually the level on the more concentrated side of the
membrane rises, while the one on the less concentrated side
falls. When the concentration is the same on both sides of the
membrane, the movement of water molecules will be the
same in both directions. At this point, the net exchange of
water is zero and there is no further change in the liquid
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

Slide 6

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Green plants absorb light energy using
chlorophyll in their leaves. They use it to react
carbon dioxide with water to make a sugar
called glucose. The glucose is used in
respiration, or converted into starch and
stored. Oxygen is produced as a by-product.
This process is called photosynthesis.
Temperature, carbon dioxide concentration
and light intensity are factors that can limit
the rate of photosynthesis.
Plants also need mineral ions, including nitrate
and magnesium, for healthy growth. They
suffer from poor growth in conditions where
mineral ions are deficient…read more

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