extracellular

Examples of extracellular in the following topics:

• Extracellular Matrix of Animal Cells

  • Most animal cells release materials into the extracellular space.
  • Collectively, these materials are called the extracellular matrix .
  • Cells have protein receptors on the extracellular surfaces of their plasma membranes.
  • An example of the role of the extracellular matrix in cell communication can be seen in blood clotting.
  • The extracellular matrix consists of a network of proteins and carbohydrates.

• Exocytosis

  • Exocytosis is the process by which cells release particles from within the cell into the extracellular space.
  • Exocytosis' main purpose is to expel material from the cell into the extracellular fluid; this is the opposite of what occurs in endocytosis.
  • This fusion opens the membranous envelope on the exterior of the cell and the waste material is expelled into the extracellular space .
  • Some examples of cells releasing molecules via exocytosis include the secretion of proteins of the extracellular matrix and secretion of neurotransmitters into the synaptic cleft by synaptic vesicles.

• Invertebrate Digestive Systems

  • Invertebrates can be classified as those that use intracellular digestion and those with extracellular digestion.
  • The alimentary canal is a more advanced digestive system than a gastrovascular cavity and carries out extracellular digestion.
  • Because the food has been broken down exterior to the cells, this type of digestion is called extracellular digestion.
  • Most invertebrates use some form of extracellular digestion to break down their food.
  • Their food is broken down in their digestive tract (extracellular digestion), rather than inside their individual cells (intracellular digestion).

• Tonicity

  • Tonicity describes how an extracellular solution can change the volume of a cell by affecting osmosis.
  • Three terms—hypotonic, isotonic, and hypertonic—are used to relate the osmolarity of a cell to the osmolarity of the extracellular fluid that contains the cells .
  • In a hypotonic situation, the extracellular fluid has lower osmolarity than the fluid inside the cell, and water enters the cell.
  • (In living systems, the point of reference is always the cytoplasm, so the prefix hypo- means that the extracellular fluid has a lower concentration of solutes, or a lower osmolarity, than the cell cytoplasm. ) It also means that the extracellular fluid has a higher concentration of water in the solution than does the cell.
  • In an isotonic solution, the extracellular fluid has the same osmolarity as the cell.

• The Complement System

  • Around 20 soluble proteins comprise the complement system, which helps destroy extracellular microorganisms that have invaded the body.
  • An array of approximately 20 types of soluble proteins, called a complement system, functions to destroy extracellular pathogens.

• Binding Initiates a Signaling Pathway

  • This type of receptor spans the plasma membrane and performs signal transduction in which an extracellular signal is converted into an intracellular signal.
  • The ligand-binding domain is also called the extracellular domain.
  • All G-protein-linked receptors have seven transmembrane domains, but each receptor has its own specific extracellular domain and G-protein-binding site.
  • When a ligand binds to the extracellular domain, a signal is transferred through the membrane, activating the enzyme.
  • The effects of extracellular signals can also be amplified by enzymatic cascades.

• Types of Receptors

  • This type of receptor spans the plasma membrane and performs signal transduction, converting an extracellular signal into an intracellular signal.
  • Each cell-surface receptor has three main components: an external ligand-binding domain (extracellular domain), a hydrophobic membrane-spanning region, and an intracellular domain inside the cell.
  • All G-protein-linked receptors have seven transmembrane domains, but each receptor has its own specific extracellular domain and G-protein-binding site.
  • The enzyme-linked receptors normally have large extracellular and intracellular domains, but the membrane-spanning region consists of a single alpha-helical region of the peptide strand.
  • Signaling molecules bind to the extracellular domain of two nearby tyrosine kinase receptors, which then dimerize.

• Components of Plasma Membranes

  • The plasma membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to the extracellular matrix and other cells to help group cells together to form tissues.
  • These proteins can be receptors, which work as receivers of extracellular inputs and as activators of intracellular processes, or markers, which allow cells to recognize each other.
  • Membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors, which then trigger intracellular responses.

• Cell Signaling and Cell Death

  • For example, most normal animal cells have receptors that interact with the extracellular matrix, a network of glycoproteins that provides structural support for cells in an organism.
  • The binding of cellular receptors to the extracellular matrix initiates a signaling cascade within the cell.
  • However, if the cell moves away from the extracellular matrix, the signaling ceases, and the cell undergoes apoptosis.

• Complex Tissue Structure

  • As multicellular organisms, animals differ from plants and fungi because their cells don't have cell walls; their cells may be embedded in an extracellular matrix (such as bone, skin, or connective tissue); and their cells have unique structures for intercellular communication (such as gap junctions).
  • This connective tissue constitutes the extracellular surroundings of cells and is made up of organic and inorganic materials.