Under which conditions will a substance be likely to enter a cell through diffusion?

A substance will enter into a cell through diffusion if a concentration gradient is present. The process of diffusion will only occur if the concentration of a substance is higher outside the cell as compared to the inside of the cell. Diffusion is the movement of particles along the concentration gradient i. e from an area of higher concentration to an area of lower concentration.

The movement of molecules against a concentration gradient is termed as active transport.