Everything Life Sciences Grade 10

FACT

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which such movement occurs includediffusion, osmosis, facilitated diffusionandactive
transport.

1. Diffusion

Diffusion is the movement of substances from a region of high concentration to low con-
centration. It is therefore said to occurdown a concentration gradient. The diagram below
shows the movement of dissolved particles within a liquid until eventually becoming ran-
domly distributed.

Figure 3.14:Diffusionis the movement of molecules from a region of higher concentration to a lower
concentration. It is a passive process (i.e. does not require input of energy).

Diffusion is apassive processwhich means it does not require any energy input. It can occur
across a living or non-living membrane and can occur in a liquid or gas medium. Due to
the fact that diffusion occurs across a concentration gradient it can result in the movement
of substances into or out of the cell. Examples of substances moved by diffusion include
carbon dioxide, oxygen, water and other small molecules that are able to dissolve within the
lipid bilayer.

Investigation: Observing diffusion

Aim:

To observe diffusion

Apparatus:

• 1 x 500 ml beaker


• large funnel


• plastic straw


• potassium permanganate crystals

Method:

1. Fill a beaker with water and allow it to stand for a few minutes so that water movement
   stops.

Chapter 3. The basic units of life 75