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In chemistry, biochemistry, and pharmacology, a dissociation constant (K D) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions.
Substrate dissociation rate contributes to how large or small the enzyme velocity will be. [2] In the Michaelis-Menten model, the enzyme binds to the substrate yielding an enzyme substrate complex, which can either go backwards by dissociating or go forward by forming a product. [2] The dissociation rate constant is defined using K off. [2]
It is usually indicated by the Greek symbol α. More accurately, degree of dissociation refers to the amount of solute dissociated into ions or radicals per mole. In case of very strong acids and bases, degree of dissociation will be close to 1. Less powerful acids and bases will have lesser degree of dissociation.
Stepwise dissociation constants are each defined for the loss of a single proton. The constant for dissociation of the first proton may be denoted as K a1 and the constants for dissociation of successive protons as K a2, etc. Phosphoric acid, H 3 PO 4, is an example of a polyprotic acid as it can lose three protons.
Stability constants defined in this way, are association constants. This can lead to some confusion as pK a values are dissociation constants. In general purpose computer programs it is customary to define all constants as association constants. The relationship between the two types of constant is given in association and dissociation constants.
This relationship can be described by a dissociation constant, which characterizes the balance between bound and unbound states for the protein-ligand system. [1] In the context of a single enzyme and a pair of binding molecules, the two ligands can be compared as stronger or weaker ligands (for the enzyme) on the basis of their dissociation ...
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
The role of water in the association equilibrium is ignored as in all but the most concentrated solutions the activity of water is constant. K is defined here as an association constant, the reciprocal of an acid dissociation constant. Each activity term { } can be expressed as the product of a concentration [ ] and an activity coefficient γ ...