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% species formation calculated with the program HySS for a 10 millimolar solution of citric acid. pK a1 = 3.13, pK a2 = 4.76, pK a3 = 6.40. When the difference between successive pK values is less than about four there is overlap between the pH range of existence of the species in equilibrium. The smaller the difference, the more the overlap.
K′ 3 describes the reaction from three states (two ligands bound) to one state (three ligands bound); hence, the apparent dissociation constant K′ 3 is three times bigger than the microscopic dissociation constant K D. The general relationship between both types of dissociation constants for n binding sites is
The Henderson–Hasselbalch equation can be used to model these equilibria. It is important to maintain this pH of 7.4 to ensure enzymes are able to work optimally. [10] Life threatening Acidosis (a low blood pH resulting in nausea, headaches, and even coma, and convulsions) is due to a lack of functioning of enzymes at a low pH. [10]
Buffer capacity falls to 33% of the maximum value at pH = pK a ± 1, to 10% at pH = pK a ± 1.5 and to 1% at pH = pK a ± 2. For this reason the most useful range is approximately pK a ± 1. When choosing a buffer for use at a specific pH, it should have a pK a value as close as possible to that pH. [2]
4] / K * S) −1. However, it is difficult to estimate K * S in seawater, limiting the utility of the otherwise more straightforward free scale. Another scale, known as the seawater scale, often denoted pH SWS, takes account of a further protonation relationship between hydrogen ions and fluoride ions, H + + F − ⇌ HF.
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 ...
The stepwise constant, K, for the formation of the same complex from ML and L is given by ML + L ⇌ ML 2; [ML 2] = K[ML][L] = Kβ 11 [M][L] 2. It follows that β 12 = Kβ 11. A cumulative constant can always be expressed as the product of stepwise constants. There is no agreed notation for stepwise constants, though a symbol such as K L
Certain ions, including Na +, K +, Ca 2+, Mg 2+, Cl −, SO 2− 4, and NO − 3 are "conservative" such that they are unaffected by changes in temperature, pressure or pH. [8] Others such as HCO − 3 are affected by changes in pH, temperature, and pressure. By isolating the conservative ions on one side of this charge balance equation, the ...