What Is Diffusion?


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Regina Bailey

** What Is Diffusion? **

By Regina BaileyAugust 31, 2012

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Diffusion of water and other molecules across a semipermeable membrane.
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Diffusion is the tendency of molecules to spread into an available space.
Without other outside forces at work, substances will diffuse from a more
concentrated environment to a less concentrated environment.

Passive transport is the diffusion of substances across a membrane. This is
a spontaneous process and cellular energy is not expended. Molecules will
move from where the substance is more concentrated to where it is less
concentrated. The rate of diffusion for different substances is affected by
membrane permeability. For instance, water diffuses freely across cell
membranes but other molecules can not. They must be helped across the cell
membrane through a process called facilitated diffusion.

Osmosis is a special case of passive transport. In osmosis, water diffuses
from a hypotonic (low solute concentration) solution to a hypertonic (high
solute concentration) solution. Generally speaking, the direction of water
flow is determined by the solute concentration and not by the "nature" of
the solute molecules themselves.

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June 17, 2013 at 12:55 pm
(1) bob says:
bit rubbish, don’t u think?!

June 18, 2013 at 10:07 am
(2) Emily says:

How would that be rubbish when it’s scientific fact…?

October 12, 2013 at 4:16 am
(3) pogi says:
some concepts and terminology are not explained very well u have to
think for a moment

Source: biology.about.com/b/2012/08/31/what-is-diffusion.htm

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