Functions of Cell Membrane:
The term cell membrane was coined by C. Nageli and C. Cramer in 1855 and the term plasmalemma has been given by J. Q. Plowe in 1931. The cell membrane also called biological membranes or biomembranes are thin quasifluid pliable film-like structure that occurs both intracellularly or around the protoplast of each cell and intracellularly or inside the cytoplasm of most cells. Cell membranes serve the following functions-
- It provides protective cover and maintains the individuality and form of the cells.
- It regulates the flow of materials in and out of the cells and between organelles and cytoplasm within the cell. A cell remains alive till the time membrane is able to determine which materials should enter or leave the cells.
- It contributes to the formation of cell organelles.
- It regulates the exit of secretions and wastes by exocytosis.
- Its intercellular junctions help in cell adhesion.
- Microvilli of plasma membrane increase the absorptive surface area of the intestine.
- Receptor molecules of the cell membrane help in the flow of information.
- Oligosaccharides of cell membrane help in cell recognition.
- Some membrane enzymes (respiratory enzymes in the inner mitochondrial membrane) participate in cellular respiration.
- The plasma membrane maintains a balance between the osmotic pressure of the cytoplasm and extracellular fluids.
- Biomembranes help in the compartmentalization of the protoplasm.
- The plasma membrane forms a sheath over cilia and flagella.
- The plasma membrane helps in cellular locomotion and cellular interaction.
- In nerve cells, the plasma membrane takes part in the transmission of impulses.
- Membrane infolds are used for bulk intake of materials by endocytosis.
- It controls and maintains the differential distribution of ions inside and outside the cells.