ENDOCYTOSIS & EXOCYTOSIS

=Endocytosis= [image:http://i.imgur.com/IEqvRK0.png?1] '''Endocytosis''' is a special form of active transport used to transport material that are too large to diffuse through the membrane to be transported through membrane proteins. Endocytosis involves absorbing materials from outside the cell by engulfing them in the cell membrane. The membrane encloses the material and buds off to form a vesicle. This often fuses with a lysosome (full of digestive enzymes) to enable the digestion of the contents. Endocytosis is often a '''receptor mediated process'''. This simply means that receptors on the cells surface will recognise particular materials and mediate their ingestion. [image:http://i.imgur.com/8gQB7g3.jpg?2] '''There are two forms of Endocytosis:''' *'''Phagocytosis''' The ingestion of solids from outside the cell. Some white blood cells ingest pathogens/foreign material. *'''Pinocytosis''' the ingestion of fluid into the cell. =Exocytosis= [image:http://i.imgur.com/dIm3f3z.jpg?1] Exocytosis is essentially just the reverse process. Materials to be ''secreted'' are transported to the cell surface in a vesicle (a small membrane bubble). The vesicle fuses with the cell membrane and its contents are released.