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Direct contact between cells allows the receptors on one cell to bind the small molecules attached to the plasma membrane of different cell. In eukaryotes, many of the cells during early development communicate through direct contact. [5] Synaptic signaling, an integral part of nervous system activity, occurs between neurons and target cells.
Hydrophobic mismatch is the difference between the thicknesses of hydrophobic regions of a transmembrane protein and of the biological membrane it spans. [1] In order to avoid unfavorable exposure of hydrophobic surfaces to water, the hydrophobic regions of transmembrane proteins are expected to have approximately the same thickness as the hydrophobic (lipid acyl chain) region of the ...
The membrane is a homogeneous substance; The electrical field is constant so that the transmembrane potential varies linearly across the membrane; The ions access the membrane instantaneously from the intra- and extracellular solutions; The permeant ions do not interact; The movement of ions is affected by both concentration and voltage differences
Exocytosis and its counterpart, endocytosis, are used by all cells because most chemical substances important to them are large polar molecules that cannot pass through the hydrophobic portion of the cell membrane by passive means. Exocytosis is the process by which a large amount of molecules are released; thus it is a form of bulk transport.
PM-ER contact sites have a well known role in the control of calcium dynamics. The major intracellular pool of calcium is the ER and its release may be triggered by different stimuli. In excitable cells the coupling between PM depolarization and the release from the intracellular pools is essential to generate the Ca 2+ signalling.
Thermodynamically the flow of substances from one compartment to another can occur in the direction of a concentration or electrochemical gradient or against it. If the exchange of substances occurs in the direction of the gradient, that is, in the direction of decreasing potential, there is no requirement for an input of energy from outside the system; if, however, the transport is against ...
A variety of cellular changes can trigger gating, depending on the ion channel, including changes in voltage across the cell membrane (voltage-gated ion channels), chemicals interacting with the ion channel (ligand-gated ion channels), changes in temperature, [4] stretching or deformation of the cell membrane, addition of a phosphate group to ...
Schematic of cell adhesion. Cell adhesion is the process by which cells interact and attach to neighbouring cells through specialised molecules of the cell surface. This process can occur either through direct contact between cell surfaces such as cell junctions or indirect interaction, where cells attach to surrounding extracellular matrix, a gel-like structure containing molecules released ...