In cell biology, molecular biology and related fields, the word extracellular (or sometimes extracellular space) means "outside the cell". This space is usually taken to be outside the plasma membranes, and occupied by fluid. The term is used in contrast to intracellular (inside the cell).

According to the [1]

The composition of the extracellular space includes metabolites, ions, various proteins and non-protein substances (i.e. DNA, RNA, lipids, microbial products etc.) that might affect cellular function. For example, hormones, growth factors, cytokines and chemokines act by travelling the extracellular space towards biochemical receptors on cells. Other proteins that are active outside the cell are various enzymes, including digestive enzymes (Trypsin, Pepsin), extracellular proteinases (Matrix metalloproteinases, ADAMTSs, Cathepsins) and antioxidant enzymes (extracellular superoxide dismutase). Often, proteins present in the extracellular space are stored outside the cells by attaching to various Extracellular matrix components (Collagens, Proteoglycans, etc.).[2] In addition, Extracellular matrix proteolytic products are also present in the extracellular space, especially in tissues undergoing remodelling [2].[3]


  1. ^ Extracellular Space by Gene Ontology database (EMBL-EBI)
  2. ^ Didangelos, A.; Yin, X.; Mandal, K.; Baumert, M.; Jahangiri, M.; Mayr, M. (2010). "Proteomics Characterization of Extracellular Space Components in the Human Aorta". Molecular & Cellular Proteomics 9 (9): 2048–2062.  .
  3. ^ Fleischhauer J, Lehmann L, Kléber AG (August 1995). "Electrical resistances of interstitial and microvascular space as determinants of the extracellular electrical field and velocity of propagation in ventricular myocardium". Circulation 92 (3): 587–94.