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Active Transport
Substances move by diffusion, osmosis and active transport:
Diffusion is the movement of particles from an area of high
concentration to an area of low concentration.
Osmosis is the diffusion of water through a partially permeable
membrane.
Active Transport is used in the digestive system when there is a low
concentration of nutrients in the gut and a high concentration of
nutrients in the bloodstream.…read more

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Oxygen needs to get from the air into the bloodstream so that it
can get to the cells for respiration by diffusion. Your cells also need to
get rid of carbon dioxide, which diffuses out of the bloodstream into air.
The lungs are protected by the ribcage, inside the thorax (this is the top
part of the body, separated from the diaphragm)
The air that you breathe in goes through the trachea. This splits into two
tubes called bronchi, one going to each lung.…read more

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Plants
Carbon dioxide enters leaf cells by diffusion. Most of the water and
mineral ions are absorbed by root hair cells.
The surface area of a plant's root is increased by root hairs
The surface area of the leaves is increased by the flattened shape and
internal air spaces
Plants have stomata to obtain carbon dioxide from the atmosphere.
The loss of water vapour from the surface of leaves is called
transpiration.…read more

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The Blood
Substances are transported around the body by the circulatory system
- the heart, the blood vessels and the blood.
The Heart
The heart pumps blood around the body. Blood flows from the heart to
the organs, through arteries, and returns from the organs, through
veins. In the organs, blood flows through capillaries. Substances needed
by cells in the body tissues pass out of the blood and into the cells.…read more

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They are packed with a red pigment called
haemoglobin.
In the lungs, haemoglobin combines with oxygen to form
oxyhaemoglobin.
In the organs, oxyhaemoglobin splits up into haemoglobin and oxygen.
Exercise
During exercise, the human body needs to react to the increased
demand for energy. The energy that is released during respiration is
used to enable muscles to contract.…read more

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The Kidneys
People whose kidneys do not function properly die because toxic
substances accumulate in their blood. Their lives can be saved by using
dialysis machines or having a healthy kidney transplanted.…read more

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To prevent rejection of the transplanted kidney:
- a donor kidney with a `tissue type' similar to that of the recipient is
used
- the recipient is treated with drugs that suppress the immune system
Micro-organisms
People from different cultures have known for thousands of years
how to use micro-organisms to make various types of food and drink
such as bread, beer, wine and yoghurt.…read more

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Micro-organisms can be grown in large vessels caller fermenters to
produce useful products.…read more

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Micro-organism Cultures
If the micro-organisms that we want to use are contaminates, the
other micro-organisms that are present may produce harmful
substances. Therefore it is only safe to use micro-organisms if we have a
pure culture containing only one particular species of micro-organism.
Micro-organisms can be grown in a culture medium containing:
-Carbohydrates, as an energy source
-Mineral ions
-Supplementary proteins and vitamins, in some cases
These nutrients are often contained in an agar medium which can be
poured into a Petri dish.…read more

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