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Under an idealized reaction condition for A + B → product in a diluted solution, Smoluchovski suggested that the molecular flux at the infinite time limit can be calculated from Fick's laws of diffusion yielding a fixed/stable concentration gradient from the target molecule, e.g. B is the target molecule holding fixed relatively, and A is the ...
An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts: The chemical gradient, or difference in solute concentration across a membrane. The electrical gradient, or difference in charge across a membrane.
Chemical diffusion occurs in a presence of concentration (or chemical potential) gradient and it results in net transport of mass. This is the process described by the diffusion equation. This is the process described by the diffusion equation.
An ion gradient has potential energy and can be used to power chemical reactions when the ions pass through a channel (red). Hydrogen ions, or protons, will diffuse from a region of high proton concentration to a region of lower proton concentration, and an electrochemical concentration gradient of protons across a membrane can be harnessed to ...
is the gradient, i.e., rate of change with position, of the logarithm of the salt concentration, which is equivalent to the rate of change of the salt concentration, divided by the salt concentration – it is effectively one over the distance over which the concentration decreases by a factor of e. The above equation is approximate, and ...
The difference between passive transport and active transport is that the active transport requires energy, and moves substances against their respective concentration gradient, whereas passive transport requires no cellular energy and moves substances in the direction of their respective concentration gradient. [10]
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.
C 0 is the initial concentration of the analyte in mol/cm 3; D is the diffusion coefficient for species in cm 2 /s; t is the time in seconds. Under controlled-diffusion circumstances, the current-time plot reflects the concentration gradient of the solution near the electrode surface.