Some molecules or particles are just too large to pass through the plasma membrane or to move through a transport protein. So cells use two other active transport processes to move these macromolecules (large molecules) into or out of the cell.
Endocytosis and Exocytosis
Endocytosis is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane.
here are three main kinds of endocytosis:
• Phagocytosis, or cellular eating, occurs when the dissolved materials enter the cell. The plasma membrane engulfs the solid material, forming a phagocytic vesicle.
• Pinocytosis, or cellular drinking, occurs when the plasma membrane folds inward to form a channel allowing dissolved substances to enter the cell.
• Receptor mediated Endocytosis

Exocytosis describes the process of vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell.

свернуть