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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.
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.
The dissociation rate constant is defined using K off. [2] The Michaelis-Menten constant is denoted by K m and is represented by the equation K m = (K off + K cat)/ K on [definition needed]. The rates that the enzyme binds and dissociates from the substrate are represented by K on and K off respectively.
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.
The Henderson–Hasselbalch equation relates the pH of a solution containing a mixture of the two components to the acid dissociation constant, K a of the acid, and the concentrations of the species in solution. [6] Simulated titration of an acidified solution of a weak acid (pK a = 4.7) with alkali
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.
Polyprotic acids are acids that can lose more than one 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. Citric acid is an example of a polyprotic acid H 3 A, as it can lose three protons.
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 ...