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pKa values for acetic, chloroacetic, dichloroacetic and trichloroacetic acids. Inductive effects and mesomeric effects affect the pK a values. A simple example is provided by the effect of replacing the hydrogen atoms in acetic acid by the more electronegative chlorine atom.
For example, acetic acid is a weak acid which has a = 1.75 x 10 −5. Its conjugate base is the acetate ion with K b = 10 −14 / K a = 5.7 x 10 −10 (from the relationship K a × K b = 10 −14 ), which certainly does not correspond to a strong base.
A "weak" polyelectrolyte, by contrast, has a dissociation constant (pKa or pKb) in the range of ~2 to ~10, meaning that it will be partially dissociated at intermediate pH. Thus, weak polyelectrolytes are not fully charged in the solution, and moreover, their fractional charge can be modified by changing the solution pH, counter-ion ...
The pH-dependence of the activity displayed by enzymes and the pH-dependence of protein stability, for example, are properties that are determined by the pK a values of amino acid side chains. The p K a values of an amino acid side chain in solution is typically inferred from the p K a values of model compounds (compounds that are similar to ...
An example is the H 2 O (water) molecule, which can gain a proton to form the hydronium ion, H 3 O +, or lose a proton, leaving the hydroxide ion, OH −. The relative ability of a molecule to give up a proton is measured by its pK a value. A low pK a value indicates that the compound is acidic and will easily give up its proton to a base.
For example, if a macromolecule M has three binding sites, K′ 1 describes a ligand being bound to any of the three binding sites. In this example, K′ 2 describes two molecules being bound and K′ 3 three molecules being bound to the macromolecule. The microscopic or individual dissociation constant describes the equilibrium of ligands ...
For example, at room temperature, in a 1-molar solution of acetic acid, only 0.001% of the acid are dissociated (i.e. 10 −5 moles out of 1 mol). Electron-withdrawing substituents, such as -CF 3 group , give stronger acids (the p K a of acetic acid is 4.76 whereas trifluoroacetic acid, with a trifluoromethyl substituent , has a p K a of 0.23).
In cell biology, protein kinase A (PKA) is a family of serine-threonine kinase [1] whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (EC 2.7.11.11). PKA has several functions in the cell, including regulation of glycogen, sugar, and lipid metabolism.