Plasma membrane or cell membrane: Just beneath the cell wall, there is a living membrane around the protoplasm, called plasma membrane or cell membrane.
It may be called by different names, such as- plasma membrane, plasmalema, cytomembrane and biomembrane etc. This membrane, at its different places, there may be some wavy folds. Each fold is called microvillus.
Structure: While giving the description of the structure the cell membrane Daielli and Dayson, at first, proposed the perfect model. Their given model is said to be Sandwich model
(i) This membrane is double layered and each layer consisting of protein and lipid.
(ii) The upper and lower layers of the double-layered membrane are composed of protein layers while the middle part is made of lipid layer.
Functions of plasma membrane:
(i) It covers all the cell elements.
(ii) It protects the inner materials from external adversity.
(iii) It acts as a frame so that special enzymes may be arranged here.
(iv) Cell materials can move through the membrane.
(v) It can synthesize different organdies. It acts as the basis of different information.
