The Fundamental Unit of Life — Science STD 9 — Question

Plasma membrane: Every cell is bounded by a thin, elastic, delicate, living membrane called plasma membrane or cell membrane. It is the outermost covering of the cell which separates the cell content from its external environment.
Plasma membrane is continuous lipid bilayer with protein molecules occurring both on inside and outside of the bilayer. We can see plasma membrane with the help of electron microscope. Structurally, plasma membrane is very flexible. The flexibility of plasma membrane helps the cell to engulf in food and other substances from its external environment.
Functions:

1. Plasma membrane is a selective permeable membrane. Therefore, it allows or permits the entry and exit of some materials in and out of the cell.
2. It protects the cell from injury.
3. The flexibility of plasma membrane helps the cell to engulf in food and other substances from its external environment. This process is known as endocytosis.
4. It bounds the semi-fluid content of the cell.