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In cell biology, diffusion is a main form of transport for necessary materials such as amino acids within cells. [1] Diffusion of solvents, such as water, through a semipermeable membrane is classified as osmosis. Metabolism and respiration rely in part upon diffusion in addition to bulk or active processes.
When a plant cell is placed in a hypotonic solution, water enters into a cell by endosmosis and as a result turgor pressure (TP) develops in the cell. The cell membrane becomes stretched and the osmotic pressure (OP) of the cell decreases. As the cell absorbs more and more water its turgor pressure increases and osmotic pressure decreases.
Membrane fluidity is known to affect the function of biomolecules residing within or associated with the membrane structure. For example, the binding of some peripheral proteins is dependent on membrane fluidity. [11] Lateral diffusion (within the membrane matrix) of membrane-related enzymes can affect reaction rates. [1]
As mentioned above, passive diffusion is a spontaneous phenomenon that increases the entropy of a system and decreases the free energy. [5] The transport process is influenced by the characteristics of the transport substance and the nature of the bilayer. The diffusion velocity of a pure phospholipid membrane will depend on: concentration ...
Techniques such as static diffusion cells (Franz cells) and flow-through diffusion cells (Bronaugh cells) have also been used. [4] The Franz Cell apparatus consists of two chambers separated by a membrane of animal or human skin. Human skin is preferred but due to ethical and other considerations is not always available.
Facilitated diffusion in cell membrane, showing ion channels and carrier proteins. Facilitated diffusion (also known as facilitated transport or passive-mediated transport) is the process of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembrane integral proteins. [1]
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low ...
Glucose uptake is the process by which glucose molecules are transported from the bloodstream into cells through specialized membrane proteins called glucose transporters, primarily via facilitated diffusion or active transport mechanisms: [1]