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In this article we will discuss about:- 1. Definition of Diffusion 2. Characteristics of Diffusion 3. Physiological Role.
Definition of Diffusion:
The spreading of solute molecules throughout the water molecules is called diffusion.
Experiment:
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When a lump of sugar is added to a glass of water, the sugar gradually disappears and, ultimately, a homogeneous solution is formed automatically. This is due to the energy possessed by all molecules which keeps them in a state of motion or vibration.
Characteristics of Diffusion:
i. Diffusion in liquids is comparatively a slow process because the molecules are so crowded together that they are continually colliding.
ii. In case of gas, diffusion is rapid.
iii. Diffusion takes place against gravity.
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Determination in a Non-Homogeneous Solution:
Diffusion between two planes X and Y in a non-homogeneous solution can be expressed quantitatively by Pick’s law as
ds/dt = DA dc/dx
where, ds/dt = The rate of movement of solute.
D = Diffusion constant.
A = The area of the planes.
dc/dx = The concentration gradient i.e. the difference in concentration between X and Y/distance between X and Y.
Physiological Role of Diffusion:
i. It helps in passive transport of substances across the cell membrane.
ii. Substances move in the direction of the physical gradients which follows the rule of diffusion.
