Substances can move into and out of a cell through its semi-permeable cell membrane. There are three different processes through which materials can move in and out of a cell. They are:
• Through the process of diffusion,
• Through the process of osmosis and
• Through the process of active transport.
Diffusion is the major process through which small molecules move in and out across the cell membrane region of higher concentration to a region of lower concentration.
The concentration of a substance is the amount of that particular substance in a given volume of liquid. Diffusion results as a result of movement and collision of molecules. The collisions of the molecules are what caused the molecules to thrust away from one another and spread out.
Molecules would normally diffuse through the cell membrane into a cell when the contents of the cell are of a lower concentration than the surrounding solution. The diffusion of water molecules through a semi permeable membrane is known as osmosis.
Due to the fact that cell function effectively without sufficient water, the majority of cellular processes depend on osmosis.
In osmosis, the molecules of water travel through the process of diffusion from a region of higher concentration to a region of lower concentration.
The movement of dissolved substances through a cell membrane without the use of cellular energy is referred to as passive transport. Diffusion and osmosis are two types of passive transport.
When there is a need for the cell to assimilate materials that are in higher concentration inside the cell than outside the cell, the movement of the materials requires energy.
On the contrary, active transport is the movement of materials through a cell membrane with the use of cellular energy. The major variation between passive transport and active transport is that active transport necessitates the use of cell’s own energy while passive transport does not.
Cells have many ways of transporting materials through active transport. In one method, especially in the transportation of protein molecules, the cell membrane “lift up” molecules outside the cell and transport them inside the cell.
Another method of active transport is through engulfing. In this case, the cell membrane envelops or engulfs a particle and forms a vacuole inside the cell.
The majority of the cells are highly small. This is because the all particles have to move in and out of the cell through the cell membrane. On entering inside the cell, it is transported to its target through a stream of moving cytoplasm.
In an extremely large cell, streams of cytoplasm ought to travel farther to transport materials from the cell membrane to every part of the cell