Difference Between Osmosis And Diffusion

Biology Tutorial

Difference Between Osmosis And Diffusion


This problem discusses the main differences between osmosis and diffusion, as they are both passive transport mechanisms but differ in terms of how these processes occur.

Sample Problem

Question source

What is the difference between osmosis and diffusion?


1) Recall that both osmosis and diffusion are examples of passive transport.
2) Passive transport involves the movement of substances across a cell membrane without the cell using energy. This contrasts with active transport, which does involve the usage of energy in the form of ATP.
3) Diffusion and osmosis can be differentiated in terms of WHAT KIND OF SUBSTANCES are participating in passive transport.
4) Diffusion is the movement of solute from a higher concentration to a lower concentration. The solute can be elements, compounds, or molecules. For instance, if you opened a bottle of perfume, the perfume molecules will spread across the room. Other people will then be able to smell the perfume from far away.
5) Osmosis, by contrast, is the movement of water across a concentration gradient (again from higher to lower concentration). This means, however, that the water is moving from an area of low solute concentration to high solute concentration.
6) This may sound counterintuitive, but think about what we are focusing on in each instance. Diffusion involves solutes, which are molecules. We are seeing molecules moving from higher to lower concentrations. Osmosis involves water, which is composed of molecules. Those water molecules are moving from areas of high water concentration to areas of low water concentration.

The answer, then, is that diffusion is the movement of solute through a cell membrane from an area of higher concentration to an area of lower concentration. However, osmosis is the movement of water from an area of higher water concentration to an area of lower water concentration.

You can look at another explanation here.

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