Explain TWO MAJOR WAYS in which LARGE PARTICLES and substanc

Explain TWO MAJOR WAYS in which LARGE PARTICLES and substances are able to ENTER and EXIT the cell.

Solution

Large particles or macromolecules are not able to diffuse through the plasma membrane into the cell. Therefore, a cell needs to engulf or expel these particles. This happen by the process of endocytosis (entry into the cell) and exocytosis (exit from the cell).

During the process of endocytosis, the plasma membranes bends and surrounds the particle forming a vesicle. Thus the vesicle slowly becomes a part of cell, it is engulfed and then digested by the cellular enzymes for its nutrients.The endocytosis process may include the phagocytosis which involves ingestion of large particles or micro-organisms or pinocytosiswhich involves ingestion of fluid and solutes. Once the target particle is engulfed, the particle pinches off from the membrane and form a membrane-bound compartment known as food vacuole, which later fuses with lysosomes.

The endocytosis may also occur through receptor proteins on the cell surface, called as receptor mediated endocytosis.

In the process of exocytosis, the particle is packaged by the endoplasmic reticulum and then buds of from the golgi appratus. And the vesicle fuses with the plasma membrane and thus its contents are transported outside the cell. The vesicles secreted out of golgi appratus may contain some specifically secreted signaling molecules by the cell or simply the waste that needs to be excreted out.