How Does Osmosis Work

How and why molecules move through a permeable membrane?

Osmosis is the movement of a solvent, such as water, across a membrane (divider) from a region of high concentration to low concentration.

The motion of molecules in an enclosed volume will always see them try to spread out equally, such as when perfume is sprayed into a room and the smell gradually dissipates as the molecules move.

Osmosis is this same effect but across a membrane, which acts as a barrier.

The membrane allows some molecules to pass through, but blocks the passage of others. Osmosis is frequently seen in animal and plant cells, where it allows the intake of useful nutrients and expels waste products.

The process ceases when the molecular concentration on either side of the membrane is uniform, a state which is referred to as isotonic.

Substances high in protein, such as eggs and milk, are less likely to undergo the process of osmosis when an animal ingests them, because the large protein molecules block the way and prevent water molecules reaching the cell membrane.

This is why eating protein-rich foods keeps your energy levels up; water is unable to leave your body, meaning cells and organs remain hydrated and functioning.