What does endocytosis mean?
Endocytosis is the process by which a living cell takes in material from its surroundings by engulfing it. The cell's outer membrane folds inward around a particle, drop of fluid, or molecule, then pinches off to form a small, sealed sac called a vesicle that carries the captured substance into the cell's interior. Biologists distinguish several forms, including phagocytosis ('cell eating'), which engulfs large particles such as bacteria, and pinocytosis ('cell drinking'), which takes in dissolved substances and fluid. A specialized form, receptor-mediated endocytosis, allows cells to import specific molecules like cholesterol after they bind to receptors on the surface. Endocytosis is fundamental to nutrition, immune defense, signaling, and the entry of some viruses and drugs into cells. Its opposite is exocytosis, the export of materials out of the cell.
nounThe biological process by which a living cell engulfs external material—such as nutrients, fluids, bacteria, or other particles—by folding its cell membrane around the substance and drawing it inward inside a membrane-bound vesicle.
- In cell biology: the active transport process in which a cell takes in extracellular material by engulfing it within a pocket of its plasma membrane that pinches off to form an intracellular vesicle.
"Macrophages defend the body by destroying bacteria they capture through endocytosis."
"The virus enters human cells through receptor-mediated endocytosis, tricking the membrane into drawing it inside."
"Under the microscope, students observed endocytosis as the amoeba engulfed a food particle."
Rarely used; the word typically appears as an uncountable mass noun referring to the general process.
"Researchers compared the endocytoses observed in both cell types."
Every time your immune system destroys a bacterium, it literally eats it alive—and that cellular swallowing is called endocytosis.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of endocytosis
Endocytosis derives from Greek roots: 'endo-' meaning 'within' and 'kytos,' meaning 'hollow vessel,' which came to denote a cell. It was coined in the early 1960s by Belgian cytologist Christian de Duve, who also coined 'exocytosis' as its counterpart, replacing the older terms phagocytosis and pinocytosis as umbrella labels for all forms of cellular intake. The same root 'kytos' underlies many cell-related terms such as cytoplasm, cytoskeleton, and cytology.
Related word forms
How endocytosis is actually used
A technical term used almost exclusively in biology, medicine, and related scientific writing; it is rarely encountered outside academic or clinical contexts. The plural 'endocytoses' exists but is seldom used.
Easily confused with endocytosis
Exocytosis is the reverse process, in which a cell expels material by fusing vesicles with its outer membrane to release contents outside the cell.