What is Extracellular Protein?
An extracellular protein is a peptide that resides in body fluids outside of cells. Extracellular fluids include interstitial fluid, or the fluid between cells; plasma, the fluid portion of blood; and cerebrospinal fluid, the fluid that bathes the brain and spinal cord. An extracellular protein can function in enzymatic action and cell recognition or signaling. Together with other organic compounds and ions, extracellular protein is important in maintaining water balance in the intracellular and extracellular spaces by acting as solutes. A solute is any molecule or compound dissolved in a fluid. A fluid containing a solute is called a solution, and it can be characterized as being hypotonic, hypertonic, or isotonic. Tonicity reflects the amount of solute in a solution. A hypotonic solution has a low solute to fluid ratio. A hypertonic solution has a high solute to fluid ratio, and an isotonic solution has an equal solute to fluid concentration. Extracellular proteins called plasma prot
