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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 ...
The grey represents the concentration of a molecule. A biomolecular gradient is established by a difference in the concentration of molecules in a biological system such as individual cells, groups of cells, or an entire organism. A biomolecular gradient can exist intracellularly (within a cell) or extracellularly (between groups of cells).
In the phenomenological approach, diffusion is the movement of a substance from a region of high concentration to a region of low concentration without bulk motion. According to Fick's laws, the diffusion flux is proportional to the negative gradient of concentrations. It goes from regions of higher concentration to regions of lower concentration.
Note that this simple theory predicts that this contribution to the diffusiophoretic motion is always up a salt concentration gradient, it always moves particles towards higher salt concentration. By contrast, the sign of the electric-field contribution to diffusiophoresis depends on the sign of β ζ {\displaystyle \beta \zeta } .
Before this point in time, a gradual variation in the concentration of A occurs along an axis, designated x, which joins the original compartments. This variation, expressed mathematically as -dC A /dx, where C A is the concentration of A. The negative sign arises because the concentration of A decreases as the distance x increases.
The process of osmosis over a semipermeable membrane.The blue dots represent particles driving the osmotic gradient. Osmosis (/ ɒ z ˈ m oʊ s ɪ s /, US also / ɒ s-/) [1] is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential ...
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]
The chemical gradient, or difference in solute concentration across a membrane. The electrical gradient, or difference in charge across a membrane. If there are unequal concentrations of an ion across a permeable membrane, the ion will move across the membrane from the area of higher concentration to the area of lower concentration through ...