Cell membrane function and difference-digieduco

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  Functions of cell membrane : (a) The proteins and enzymes present in the cell membrane helps in the transport of certain substances like sugar, sodium and other ions etc. across the cell membrane. (b) Cell membrane protects the internal structures of the cell and different organelles of the cytoplasm. (c) It maintains the shape of the cell. (d) It acts as a selective permeable membrane because it allows to pass certain substances while others are not, hence it helps in the transport of selective materials from and to the cells. (e) The membranes on the cytoplasmic organelles and nucleus most probably formed from the plasma membrane. (f) Other important functions of cell membrane of the cells are endocytosis and exocytosis . Endocytosis is the process by which materials are transported into the cells by the formation of vesicles. It includes two processes-phagocytosis (cell eating) and pinocytosis (cell drinking). The reverse process of endocytosis is exocytosis. During this p
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Structure of a typical plant cell-digieduco

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A typical structure of a plant cell consists of a centrally situated separable mass or unit-the protoplast and the surrounding membrane or wall known as the cell wall. In plants therefore, the term cell includes the protoplast together with the wall.
Structure of a typical plant cell-digieduco

(a) CELL WALL :-It is the non-living boundary wall of a cell, mainly composed of cellulose but often chemically altered by other protoplasmic secretions. Cell wall encloses , a space known as cell cavity or cell lumen in which protoplast occurs. Plant cell wall may be a primary wall only or may comprise both primary and secondary walls ; depressions or pits may be present in the cell wall and the wall may be traversed by cytoplasmic strands known as plasmodesmata.

Functions :--(i) Cell wall gives a definite shape to the cell, (ii) It protects the protoplasm from external injury and (iii) allows water and mineral salts to pass through it.

(b) THE PROTOPLAST :-The protoplast is the organised mass that lies within the wall. The constituents of the protoplast are divided into two groups, viz. (I) protoplasmic components i.e. protoplasm and (II) non-protoplasmic components. To the protoplasmic component belongs the cytoplasm, the living basic substance of the cell in which other specialised protoplasmic organelles such as endoplasmic reticulum (ER), nucleus, plastids, mitochondria, ribosomes, spherosomes, Golgi apparatus or complex (i.e. dictyosomes), microbodies, microtubules, centrosomes (in the cells of some thallophytes) etc. are located as living cell inclusions. To the non-protoplasmic component belongs the (i) ergastic substances i.e. non-living cell inclusions like reserve food materials, exeretory materials, secretory materials etc. and (ii) the vacuole (Esau, 1965).

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