BIOCHEM ACS STUDY GUIDE
PRACTICE PACK 2026 TESTED
QUESTIONS AND ANSWERS
◉ What is a zwitterion?
Answer: A molecule with both positive and negative charges but overall
neutral.
◉ What is pKa?
Answer: The pH at which a group is 50% protonated.
◉ What is pI?
Answer: The pH where the amino acid has no net charge.
◉ When pH < pKa, what happens?
Answer: The group is protonated.
◉ When pH > pKa, what happens?
Answer: The group is deprotonated.
◉ What bond links amino acids?
Answer: Peptide bond (amide linkage).
◉ What is special about the peptide bond?
, Answer: Planar with partial double-bond character.
◉ Which amino acids are acidic?
Answer: Asp, Glu.
◉ Which amino acids are basic?
Answer: Lys, Arg, His.
◉ Which amino acids are aromatic?
Answer: Phe, Tyr, Trp.
◉ Which amino acid forms disulfide bonds?
Answer: Cysteine.
◉ Which amino acid is rigid?
Answer: Proline.
◉ Which amino acid is most flexible?
Answer: Glycine.
◉ What determines amino acid charge?
Answer: pH relative to pKa values.
PRACTICE PACK 2026 TESTED
QUESTIONS AND ANSWERS
◉ What is a zwitterion?
Answer: A molecule with both positive and negative charges but overall
neutral.
◉ What is pKa?
Answer: The pH at which a group is 50% protonated.
◉ What is pI?
Answer: The pH where the amino acid has no net charge.
◉ When pH < pKa, what happens?
Answer: The group is protonated.
◉ When pH > pKa, what happens?
Answer: The group is deprotonated.
◉ What bond links amino acids?
Answer: Peptide bond (amide linkage).
◉ What is special about the peptide bond?
, Answer: Planar with partial double-bond character.
◉ Which amino acids are acidic?
Answer: Asp, Glu.
◉ Which amino acids are basic?
Answer: Lys, Arg, His.
◉ Which amino acids are aromatic?
Answer: Phe, Tyr, Trp.
◉ Which amino acid forms disulfide bonds?
Answer: Cysteine.
◉ Which amino acid is rigid?
Answer: Proline.
◉ Which amino acid is most flexible?
Answer: Glycine.
◉ What determines amino acid charge?
Answer: pH relative to pKa values.
