Recycling of Plasma Membrane Components
During exocytosis secretory vesicles fuse with plasma membrane, adding to the membrane surface area. Yet, the surface area of plasma membrane remains constant. This is due to recycling of the membrane components. This recycling is carried out by subsequent return of the internalised membrane components and by removal of excess membrane through internalisation. For example, plasma membrane of thyroid cells can bind wiih ferritin, endocytosis is induced by addition of thyrotropin to the cells. Immediately after endocytocis, ferritin appears in lysosomes, and within 30 minutes it can be detected in cisternae of Golgi complex.Likewise, endocytosis results in the internationalisation of plasma membrane. Golgi components may reprocess and reuse the membrane components after endocytosis, and use them ,secretion, lysosome formatidn or restoration of plasma membrane itself. That is how the Golgi apparatus functions in recycling of the membrane components.