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 th...
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Endoplasmic reticulum (ER)-digieduco

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Previously the cytoplasm was considered to be structureless, but with the help of electron microscope an intricate membranous structure within the cytoplasm has been discovered. That structure is known as endoplasmic reticulum which consists of two lipoproteinaceous unit-membranes forming a canal-like anastomosing system. Generally three main types of endoplasmic reticulum are found e.g. long flattened units called cistemae, round units called vesicles and tube-like irregular units called tubules.
Endoplasmic reticulum (ER)-digieduco

The endoplasmic reticulum may be smooth (non-granular) or rough (granular)-the latter type bears ribosomes . Sometime the ER occurs in the cytoplasmic strands. plasmodesmata traversing the cell wall of neighbouring cells. The portion of ER situated in tubular form in the centre of the plasmodesmata is called desmotubule. The main function of endoplasmic reticulum is to increase surface area within the cytoplasm for various metabolic activities, it also helps in translocation of metabolites and their storage within the vacuoles. It also plays an important role in cell wall formation, and also establishes the plane of cell division by the provision and transport of materials to be incorporated in the cell plate (Cutter, 1978). There are also views that the ER gives rise to membranes of Golgi bodies and microbodies.

Membranes of more or less similar structure are also found on the external surface of the cytoplasm i.e. ectoplasm and on the layer bordering the vacuoles Le. tonoplasm. 

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