BASIC - Lysine and arginine exist in the charged form...

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BASIC Three amino acids have basic R-groups: lysine, arginine, and histidine Addition of a hydrogen ion converts the free (second) amino group of lysine or arginine to the positively charged form NH3+. A proton can similarly be added to the histidine ring making it positively charged. Important point: charge of the side group will depend upon the pH of the surrounding solution.
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Unformatted text preview: Lysine and arginine exist in the + charged form within the cell (pH 6-8). Histidine can be either uncharged or charged at physiological pH so it frequently plays an active role in enzymatic reactions involving the exchange of H ions. The basic amino acids are polar and hydrophilic and, therefore, would normally be found on the outer surface of a protein....
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