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The Scientific Research Notes of S. Sunkavally (years: 2002-2011).

3728-3729.

#lysosomes #lens #eye #enzymes #isoelectric point #alleles #Mutation #light chain #heavy chain #nano-tube #antigen #fever #ice #carboxylic acids #amino acids #fatty acids #sodium #potassium

The Scientific Research Notes Of S. Sunkavally (years: 2002-2011).

3105.

#isoelectric point #charge #zwittterion #alanine #chremistry #solutions #protien #amino acid

If the pH is greater than the pKa of a group, the group will lose its proton. If the pH is lower than the pKa of a group, then the group will gain a proton.

#pH #isoelectric point #amino acid #chemistry

What is Zwitter Ion and Isoelectric point

Amino acidshave at lease two ionizable groups, i.e., -COOH and -NH2+, of which the former dissociates more easily than the latter. at physiological pH (7.3), the carboxyl group exists in ionized form whereas the amino group remains un-dissociated and thus retains a positive charge. This doubly charged molecule of amino acid containing a negative and a positive charged group is electrically…

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#dipolar ions #Isoelectric point #isoelectric point of insulin #isoelectric point of lysozyme #Zwitter Ion

Decreasing the pH of an amino acid that is at its isoelectric point will cause it to become positively charged.

#isoelectric point #pI #organic chemistry

Isoelectric Point

Amino Acids have both amino group as well as a carboxylic acid group. The pKa values of both the groups are well separated that at any given pH a molecule of amino acids carries some charge. For example at a pH as low as 1, the amino group will be protonated and the net charge of the molecule will be positive and at a pH as high as 12 the acidic hydrogen atoms will be removed and the net charge on the molecule will be negative. So, at normal biological pH, most amino acids have the amino group protonated and the carboxylic acid group deprotonated. This ionic structure is called the zwitter ion.

The various forms that an amino acid takes with increase in pH is shown below.

At a lower pH (pH = 2) the amino acid is positively charged and as we increase the pH and move to a higher pH (pH = 12) the amino acid becomes negatively charged. At a lower pH the concentration of the cation (A)is more than that of the anion (C) and as the pH increases the concentration of the anion also increases and becomes more than that of the cation. This implies that at a particular pH the concentration of both the cation and the anion should be equal. This pH at which the concentrations of both the cation and anion are equal is called as the Isoelectric Point of the amino acid.

Generally isoelectric point of an amino acid is the average of both the pKa values.

Ka1 = ([B][H+])/[A]

So, [A] = ([B][H+])/Ka1

Ka2 = ([C][H+])/[B]

So, [C] = (Ka2 [B])/[H+]

At Isoelectric Point, [A] = [C]

So,

([B][H+])/Ka1 = (Ka2 [B])/[H+]

Rearranging the above expressions we get the following

[H+]2 = Ka1 * Ka2

or pH = (pKa1 + pKa2) / 2

There are some amino acids which have an acid or basic side chain which will lead to an additional Ka value. In such cases, the average of the pKa values on either side of the zwitter ion is the isoelectric point.

In the above case Isoelectric point is the average of pKa2 and pKa3 values.

In the above case Isoelectric point is the average of pKa1 and pKa2 values.

#chemistry #organic chemistry #amino acids #biomolecules #isoelectric point #zwitter ions

Question on Amino Acids

If, at at room temperature, the isoelectric point of an amino acid is 5 and is kept in a medium of pH = 7, will the concentration of the cationic form be more or the anionic form?

#Chemistry #organic chemistry #amino acids #pI #isoelectric point