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Intracellular transport is an overarching category of how cells obtain nutrients and signals. One very well understood form of intracellular transport is known as endocytosis. Endocytosis is defined as the uptake of material by the invagination of the plasma membrane. [4]
Connexons will form the gap junction by docking a hemi-channel to another hemi-channel in an adjacent cell membrane. [2] During this phase, the formation of intercellular channels spanning both of the plasma membranes occurs. Subsequently, this process leads to a better understanding of how electric synapses are facilitated between neurons. [2]
The major route for endocytosis in most cells, and the best-understood, is that mediated by the molecule clathrin. [19] [20] This large protein assists in the formation of a coated pit on the inner surface of the plasma membrane of the cell. This pit then buds into the cell to form a coated vesicle in the cytoplasm of the cell.
The ligand and receptor will then recruit adaptor proteins and clathrin triskelions to the plasma membrane around where invagination will take place. Invagination of the plasma membrane then occurs, forming a clathrin-coated pit. [1] Other receptors can nucleate a clathrin-coated pit allowing formation around the receptor.
The plasma membrane accounts for around 2% of the total membrane in the cell, whereas intracellular organelles contain 98% of the cell's membrane. The major intracellular compartments are endoplasmic reticulum, Golgi apparatus, and mitochondria. On the basis of localization, ion channels are classified as: Plasma membrane channels
Each gap junction is composed of two hemichannels, or connexons, which consist of homo- or heterohexameric arrays of connexins, and the connexon in one plasma membrane docks end-to-end with a connexon in the membrane of a closely opposed cell. The hemichannel is made of six connexin subunits, each of which consist of four transmembrane segments.
Membrane channels are a family of biological membrane proteins which allow the passive movement of ions (ion channels), water or other solutes to passively pass through the membrane down their electrochemical gradient. They are studied using a range of channelomics experimental and mathematical techniques.
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).