Passive Transport Versus Active Transport

Passive transport involves carriers, channels, or direct diffusion through a membrane.
This type of transport always operates from regions of greater concentration to regions of lesser concentration.  
No external source of energy is required.

Examples of passive transport include
·Simple diffusion
·Channel diffusion
·Facilitated diffusion

There are two types of active transport:
·Primary active transport
·Secondary active transport.

In active transport it is possible to go against the concentration gradient. 
In active transport, a source of energy is required to move the carrier and its materials.

Primary Active Transport directly uses ATP.  An example of primary active transport is the sodium pump.

Secondary active transport does not directly use ATP. 
It takes advantage of a previously existing concentration gradient (via carriers).

An example of the body needing to move against the concentration gradient
can be found in looking at glucose in the intestine.
intestine.gif (2082 bytes)

The body has to move glucose against the concentration gradient.

There are three types of transport proteins:  channels, carriers, and pumps

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carriers.gif (2852 bytes)





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