Endocytosis
Endocytosis is the process by which a cell takes in material from outside by folding its plasma membrane inward and pinching off a membrane-bound vesicle. It lets cells import nutrients, signals and particles that are too large to pass through channels.
Endocytosis is the process by which a cell takes in material from outside by folding its plasma membrane inward and pinching off a membrane-bound vesicle. It lets cells import nutrients, signals and particles that are too large to pass through channels.
Types: How Do Cells Take Things In?
In phagocytosis, "cell eating," a cell engulfs large particles such as bacteria or dead cells, the job of immune cells like the macrophage. In pinocytosis it samples droplets of fluid. In receptor-mediated endocytosis, receptors bind specific cargo and gather in clathrin-coated pits, which form vesicles. Caveolae, small flask-shaped pits, form another route.
Machinery: What Pinches the Vesicle Off?
The clathrin coat shapes the pit, adaptor proteins pick cargo, and the GTPase dynamin forms a ring around the neck to cut it free. The actin cytoskeleton helps drive large events. The new vesicle fuses with early endosomes, where contents are sorted: receptors are recycled, and the rest passes to lysosomes for breakdown.
Importance: Why Does It Matter for Health?
Cells take in cholesterol carried by LDL particles by endocytosis of the LDL receptor, and defects in this lead to familial hypercholesterolemia. Many viruses hijack endocytosis to enter cells. The opposite process, exocytosis, releases material, and the whole system moves membrane through the cell's Golgi apparatus and other compartments.
Endocytosis at a Glance
| Property | Value |
|---|---|
| Main types | Phagocytosis, pinocytosis, receptor-mediated |
| Key coat | Clathrin |
| Opposite process | Exocytosis |
See Also
- Cell Membrane — the barrier that is folded inward
- Macrophage — a cell specialized for phagocytosis
- Golgi Apparatus — a hub of membrane trafficking