The random movement of molecules is called diffusion. Although individual molecules move randomly, a substance can have directed movement, or net diffusion. The net diffusion of a substance occurs because of a difference in its concentration, or gradient , along its course. Within an animal's body as oxygen is used up and carbon dioxide produced, the concentration gradient of the two gases provides the direction for their diffusion. For example, as air or water nears the respiratory membrane, the oxygen concentration on the outside of the membrane is higher than on the internal side so oxygen diffuses inward. The concentration gradient for carbon dioxide is in the opposite direction, and so net diffusion of carbon dioxide keeps it diffusing out of the body.
Read more: http://www.biologyreference.com/Fo-Gr/Gas-Exchange.html#ixzz3bjA1v9hV
The random movement of molecules is called diffusion. Although individual molecules move randomly, a substance can have directed movement, or net diffusion. The net diffusion of a substance occurs because of a difference in its concentration, or gradient , along its course. Within an animal's body as oxygen is used up and carbon dioxide produced, the concentration gradient of the two gases provides the direction for their diffusion. For example, as air or water nears the respiratory membrane, the oxygen concentration on the outside of the membrane is higher than on the internal side so oxygen diffuses inward. The concentration gradient for carbon dioxide is in the opposite direction, and so net diffusion of carbon dioxide keeps it diffusing out of the body.Read more: http://www.biologyreference.com/Fo-Gr/Gas-Exchange.html#ixzz3bjA1v9hV
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