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Non-Ionizable Vs. Ionizable R-Groups quiz

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  • What is the main difference between non-ionizable and ionizable R groups in amino acids?
    Non-ionizable R groups cannot gain a charge and lack acid-base reactions, while ionizable R groups can gain a charge through acid-base reactions.
  • How many pKa values do amino acids with non-ionizable R groups have?
    They have two pKa values: one for the amino group and one for the carboxyl group.
  • How many amino acids have non-ionizable R groups?
    There are 13 amino acids with non-ionizable R groups.
  • How many pKa values do amino acids with ionizable R groups have?
    They have three pKa values: one for the amino group, one for the carboxyl group, and one for the R group.
  • How many amino acids have ionizable R groups?
    There are 7 amino acids with ionizable R groups.
  • Which amino acids have positively charged R groups at physiological pH?
    Arginine, histidine, and lysine have positively charged R groups at physiological pH.
  • Which amino acids have negatively charged R groups at physiological pH?
    Aspartate (aspartic acid) and glutamate (glutamic acid) have negatively charged R groups at physiological pH.
  • Which two amino acids have ionizable R groups but are uncharged at physiological pH?
    Cysteine and tyrosine have ionizable R groups but are uncharged at physiological pH.
  • What is the pKa of cysteine’s R group, and what happens when the pH is above this value?
    Cysteine’s R group pKa is 8.3; above this pH, it donates a hydrogen and gains a negative charge.
  • What is the pKa of tyrosine’s R group, and what happens when the pH is above this value?
    Tyrosine’s R group pKa is 10.1; above this pH, it donates a hydrogen and gains a negative charge.
  • Why can amino acids with ionizable R groups form ionic bonds?
    Because their R groups can gain or lose charges through acid-base reactions, allowing them to participate in ionic interactions.
  • What mnemonic helps remember the seven amino acids with ionizable R groups?
    The mnemonic is 'yucky crazy dragons eat knights riding horses,' representing tyrosine, cysteine, aspartate, glutamate, lysine, arginine, and histidine.
  • At physiological pH, which ionizable amino acids are uncharged?
    Cysteine and tyrosine are uncharged at physiological pH.
  • What is the significance of understanding ionizable R groups in biochemistry?
    It is crucial for understanding charge–charge interactions and protein structure-function relationships.
  • How do non-ionizable R groups affect an amino acid’s ability to form ionic bonds?
    Amino acids with non-ionizable R groups cannot form ionic bonds because their R groups do not gain or lose charges.