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The Kidneys
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Nervous System
Vessels and Blood

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Cell Biology
Human Biology
Plant Biology

Animal Cells

A Typical Animal Cell

animal cell diagram

This is a diagram of a simple, animal cell. There are three main components.
Cell membrane this is a layer covering the cell that controls what goes in and out of it. Like a sac holding everything together.
Nucleus this contains genetic material and controls the actions of the cell.
Cytoplasm the liquid that makes up the majority of the cell, it is where chemical reactions take place.

Diffusion, Osmosis and Active Transport

Substances will move through the membrane by diffusion. This is the random spreading out of particles until they are even. For example, when you put your instant coffee in boiling water, the coffee particles spread out and fill the entire mug, this is diffusion.

A second way that substances can move through the cell membrane is by osmosis. This is a special type of diffusion where water moves from a high to a low concentration through a 'partially permeable membrane', or a membrane specially shaped to only allow water molecules through.
To learn about Osmosis in more detail visit Osmosis

A final way that substances can be moved through a membrane is active transport. This is where important substances are moved by the membrane. This process requires energy.

All Together Now!

Now obviously every single cell in your body does not look like the very simple one shown above. Millions of specially adapted cells must all work together to achieve the desired functions

An example of one of these specially adapted cells is a nerve cell:

nerve cell diagram

To begin with, this cell has a myelin sheath this is a layer of fat containing cells which insulate and therefore speeds up the impulse. The second feature is the projections and divisions going into and out, this allows it to receive and send impulses to many other cells. A final feature about the nerve cell is it's length this allows it to send impulses long distances.
For more on nerves see Nervous System