The movement of water from an area of high water concentration to an area of low water concentration is known as osmosis. Diffusion is also one such mechanism in which particles move from high concentration to low concentration. But, there is a difference between diffusion and osmosis. In osmosis, the movement occurs through a semi-permeable membrane. In cells, plasma membrane acts as semi-permeable membrane. Osmosis is a very important phenomenon to sustain life in biological systems because it helps in maintaining homeostasis. Homeostasis on the other hand is a process which aids living beings in regulating their daily activities so as to maintain stable internal environment. For example, if a cell becomes dehydrated (flaccid cell), then it can be easily rehydrated by keeping it in an environment full of water i.e. a hypertonic solution . The water will enter into the cell by osmosis thereby making it rehydrated again.
