How Does Diffusion Differ From Osmosis?

What is Simple Diffusion?

Molecules have kinetic energy, which means they're in constant motion. When they're dissolved in a solution, they distribute themselves evenly throughout it. A well-known example of diffusion can be seen by dissolving sugar in water.

Sugar in Water

During diffusion, molecules move from high to low concentrations. For example, envision a lump of sugar at the bottom of a glass of water. As the solution sits, the sugar molecules are constantly moving away from each other until they are spread evenly through the solution.

Rate of Diffusion and the Concentration Gradient

The length of time it takes for molecules to become evenly distributed is called the rate of diffusion. The size of molecules, their temperature and the difference in concentration all affect the rate of diffusion. The difference in concentration is called the concentration gradient.

Passive Transport

In cells, diffusion explains the process where molecules move in and out of a cell and its surrounding environment. Diffusion is passive transport. Passive transport means that molecules move in and out of a cell along the concentration gradient. Diffusion does not require the aid of energy or transport proteins.

Active Transport and Osmosis

Osmosis is a form of active transport. Osmosis specifically refers to the movement of water molecules from low water concentration to high water concentration through a semi-permeable membrane. An area of low water concentration is also known as an area of high water potential. An area of high water concentration is also known as an area of low water potential.

Hypertonic and Hypotonic

During osmosis, a cell in a low water concentration area (hypertonic) loses water and shrinks. A cell in a high water concentration area (hypotonic) takes in water and swells or even bursts.

The Basic Difference Between Diffusion and Osmosis

Diffusion is a process by which molecules move away from higher concentrations to evenly distribute throughout a solution.

Osmosis is a process of diffusion by which water molecules move toward higher concentrations, in and out of a cell.

Resources

• Video and Quiz About Simple Diffusion
• Transport Across Cell Membranes In Depth
• Biology-Online Dictionary