endocytosis exocytosis

Endo-, Trans-, Exocytosis

1. Coated pit ingests substance

2. Protein coated vesicle detaches

3. Coat proteins detach and are recycled to plasma membrane 

4. Uncoated vesicle fuses with a sorting vesicle called an endosome 

5. Transport vesicle containing membrane components moves to the plasma membrane for recycling

6. Fused vesicle may fuse with lysosomes for digestion of its components OR deliver its contents to the plasma membrane i the opposite side of the cell (transcytosis)

Receptor Mediated endocytosis

• Extracellular substances bind:

-receptor proteins

- concentrates substance in protein-coated vesicle 

• Lipids may be released in the cell, or combined with a lysosome to digest contents

• Receptors are recycles to the plasma membrane in vesicles 

Endocytosis: phagocytosis

• Common function macrophages 

Endocytosis: Pinocytosis

• The cell “gulps” drops of extracellular fluid containing into tiny vesicles 

• No receptors are used, so the process is nonspecific 

• Most vesicles are protein- coated 

Exocytosis and endocytosis transport across a membrane