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Titrations of Amino Acids with Ionizable R-Groups definitions

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  • Amino Group
    A functional group in amino acids with a typical pKa around 9–10.5, contributing to the molecule's charge during titration.
  • Carboxyl Group
    A functional group in amino acids with a typical pKa near 2, responsible for the first inflection and equivalence point in titration curves.
  • R Group
    A side chain in certain amino acids that can ionize, adding a third titratable group and affecting the titration curve.
  • Histidine
    An amino acid with an ionizable R group, showing three distinct pKa values and equivalence points in its titration curve.
  • Titration Curve
    A graphical representation showing pH changes as titrant is added, revealing inflection and equivalence points for ionizable groups.
  • Inflection Point
    A spot on the titration curve where the slope changes, corresponding to the midpoint of protonation or deprotonation for a group.
  • Equivalence Point
    A position on the titration curve where an ionizable group is fully neutralized, marked by a vertical line and a change in net charge.
  • pKa
    A value indicating the pH at which half of a specific ionizable group is deprotonated, marking a midpoint on the titration curve.
  • Isoelectric Point
    The pH at which the net charge of an amino acid's predominant structure is zero, calculated as the average of two relevant pKa values.
  • Conjugate Acid
    The protonated form of an ionizable group, predominating at pH values below its pKa.
  • Conjugate Base
    The deprotonated form of an ionizable group, predominating at pH values above its pKa.
  • Net Charge
    The sum of charges on all ionizable groups in an amino acid, changing as pH crosses each pKa during titration.
  • Predominant Structure
    The most common form of an amino acid at a given pH, determined by the protonation states of its ionizable groups.
  • Molar Equivalent
    The amount of titrant added relative to the amino acid, used to identify equivalence points during titration.
  • Seven Amino Acids
    A group of amino acids with ionizable R groups, remembered by a mnemonic, each showing three titratable groups in their curves.