Endocytosis and exocytosis are active transport mechanisms that cells use to transport macromolecules that are too large to pass through the cell membrane passively.
Features of Endocytosis
- Process by which cells actively transport substances into a cell by engulfing them in a vesicle.
- Decreases the size of the cell membrane.
- Helps to absorb nutrients for efficient cellular functioning and eliminate pathogens and old or damaged cells.
- Occurs over three pathways – phagocytosis, pinocytosis, and receptor-mediated endocytosis.
- Vesicle is formed from cell membrane. It then gets into the cytoplasm.
- Example of endocytosis - White blood cells being engulfed by phagocytes.
Features of Exocytosis
- Process by which cells actively expel molecules out of the cell into the extracellular fluid.
- Increases the size of the cell membrane.
- Facilitates communication between cells, repairs cell membrane, and eliminates toxins and waste products.
- Occurs through three pathways – regulated, constitutive, and fusion of vesicles with lysosomes
- Vesicle is formed in the Golgi apparatus. It then fuses with the cell membrane.
- Example of exocytosis - Releasing neurotransmitters to facilitate cellular communication