What does endosome mean?
An endosome is a membrane-bound compartment inside eukaryotic cells that serves as a key station in intracellular transport. When a cell engulfs material from its surroundings through endocytosis — nutrients, signaling receptors, or even pathogens — the engulfed cargo is first delivered to an endosome. Acting much like a sorting depot, the endosome determines each item's fate: some cargo is recycled back to the cell surface, while the rest is routed onward to lysosomes, where it is broken down. Endosomes mature over time, progressing from 'early' endosomes near the cell's edge to 'late' endosomes deeper in the cytoplasm, each stage marked by changes in their protein and lipid composition. The word derives from Greek roots meaning 'within' and 'body'. Although strictly a term of cell biology rather than everyday speech, the endosome is central to understanding how cells communicate, feed themselves, and defend against infection.
nounA membrane-bound compartment found within the cytoplasm of eukaryotic cells that sorts and transports material taken up from the cell surface, directing it to destinations such as lysosomes for degradation or recycling back to the membrane.
- (cell biology) A membrane-bound cytoplasmic organelle that receives material internalized by endocytosis and sorts it for transport to lysosomes or other destinations.
"Receptor-bound ligands are internalized by the cell and delivered to the endosome, where they are sorted for degradation or recycling."
"The virus fuses with the endosomal membrane to release its genetic material into the cytoplasm."
"Under the electron microscope, early endosomes appeared as small tubular-vesicular structures near the cell periphery."
Standard English plural; commonly used when referring to populations or classes of these organelles.
"Late endosomes migrate toward the Golgi apparatus along microtubules."
Every time your cell swallows something from outside — a nutrient, a signal molecule, even a virus — it first passes through the endosome, the cell's molecular sorting office deciding what gets destroyed and what gets recycled.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of endosome
The term endosome was coined in the twentieth century from Greek roots: 'endo-' meaning 'within' or 'inside', and '-some' from 'sōma', meaning 'body'. It follows the naming pattern of other cell structures such as chromosome ('colored body') and lysosome ('dissolving body'), which likewise pair a Greek descriptive element with 'sōma'. The word entered scientific usage as cell biologists identified these distinct trafficking compartments using microscopy and biochemical fractionation techniques.
Related word forms
How endosome is actually used
Strictly a technical term used in cell biology and biochemistry; rarely encountered in general conversation. In research literature it is often modified as 'early', 'late', or 'recycling' endosome to denote stages in the maturation pathway. Plural: endosomes; the adjective 'endosomal' is common in phrases such as 'endosomal pathway'.
Easily confused with endosome
A lysosome is the degradative organelle that breaks down cellular waste, whereas an endosome is a trafficking compartment that sorts internalized material, often delivering it to lysosomes.