Diffusion

Cells make up every living things. One important part of a cell is the cell membrane. The cell Membrane is a thin protective coating around a cell that regulates what goes in and out of the cell. An important part of regulating this is passive transport.
Passive transport is the movement of materials through membranes without any input of energy. One type of passive transport is diffusion. Passive transport is the diffusion of substances across a membrane. In diffusion, molecules will usually move from where the substance is more concentrated to where it is less concentrated. The molecules also tend to spread out in the space they enter just like food coloring in water. Water diffuses freely across membranes, an obvious benefit for cells since water is crucial to many cellular processes. Some molecules however must be helped across the cell membrane through a process called facilitated diffusion. Another type of passive transport is facilitated diffusion. Facilitated diffusion is the type of passive transport that allows substances to cross cell membranes with the help of special transport proteins. The proteins help let in molecules that would otherwise not be able to get in. The last kind of diffusion is osmosis. In plant cells, water is constantly diffusing into the cell. If the concentration of water is higher outside the cell than inside, water moves into the cell. If the concentration of water is lower outside a cell, water moves out of the cell. It is easy to see the effects of osmosis on plants. When you forget to water the plant, the soil becomes dry. If the soil is dry, there is no water to soak up. As a result, the water leaves the plant through osmosis leaving it wilted. This means the leaves will shrink. If you water the plant, it will soak up all the water through osmosis and it will look normal again.
Cells benefit from passive transport because some materials can move through various cell membranes without any input of energy.