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Bi
olo gy
GC S E
U nit
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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…

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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…

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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…

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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,…

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have no nucleus. 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…

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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.

A healthy kidney produces urine by:
First, filtering the blood
Reabsorbing all the sugar
Reabsorbing all the dissolved…

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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…

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Micro-organisms can be grown in large vessels caller fermenters to
produce useful products. Industrial fermenters usually have:
An air supply - to provide oxygen for respiration of the micro-organisms
A stirrer - to keep the micro-organisms in suspension and maintain an
even temperature
A water-cooled jacked - to remove heat…

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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…

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