ACS Biochemistry Exam A+ Questions
and Answers Verified Solutions Latest
Update 2026/2027
Question:
FMOC Chemical Synthesis
Answer:
Used in synthesis of a growing amino acid chain to a polystyrene bead. FMOC is used as a
protecting group on the N-terminus.
Question:
Salting Out (Purification)
Answer:
Changes soluble protein to solid precipitate. Protein precipitates when the charges on the protein
match the charges in the solution.
Question:
Size-Exclusion Chromatography
Answer:
Separates sample based on size with smaller molecules eluting later.
Question:
Ion-Exchange Chromatography
Answer:
Separates sample based on charge. CM attracts +, DEAE attracts -. May have repulsion effect on
like charges. Salt or acid used to remove stuck proteins.
,Question:
Hydrophobic/Reverse Phase Chromatography
Answer:
Beads are coated with a carbon chain. Hydrophobic proteins stick better. Elute with non-H-bonding
solvent (acetonitrile).
Question:
Affinity Chromatography
Answer:
Attach a ligand that binds a protein to a bead. Elute with harsh chemicals or similar ligand.
Question:
SDS-PAGE
Answer:
Uses SDS. Gel is made from cross-linked polyacrylamide. Separates based off of mass with smaller
molecules moving faster. Visualized with Coomassie blue.
Question:
SDS
Answer:
Sodium dodecyl sulfate. Unfolds proteins and gives them uniform negative charge.
Question:
Isoelectric Focusing
Answer:
Variation of gel electrophoresis where protein charge matters. Involves electrodes and pH gradient.
Protein stops at their pI when neutral.
Question:
,FDNB (1-fluoro-2,3-dinitrobenzene)
Answer:
FDNB reacts with the N-terminus of the protein to produce a 2,4-dinitrophenol derivative that
labels the first residue. Can repeat hydrolysis to determine sequential amino acids.
Question:
DTT (dithiothreitol)
Answer:
Reduces disulfide bonds.
Question:
Iodoacetate
Answer:
Adds carboxymethyl group on free -SH groups. Blocks disulfide bonding.
Question:
Homologs
Answer:
Shares 25% identity with another gene
Question:
Orthologs
Answer:
Similar genes in different organisms
Question:
Paralogs
Answer:
, Similar "paired" genes in the same organism
Question:
Ramachandran Plot
Answer:
Shows favorable phi-psi angle combinations. 3 main "wells" for α-helices, ß-sheets, and
left-handed α-helices.
Question:
Glycine Ramachandran Plot
Answer:
Glycine can adopt more angles. (H's for R- group).
Question:
Proline Ramachandran Plot
Answer:
Proline adopts fewer angles. Amino group is incorporated into a ring.
Question:
α-helices
Answer:
Ala is common, Gly & Pro are not very common. Side-chain interactions every 3 or 4 residues.
Turns once every 3.6 residues. Distance between backbones is 5.4Å.
Question:
Helix Dipole
Answer:
Formed from added dipole moments of all hydrogen bonds in an α-helix. N-terminus is δ+ and
C-terminus is δ-.
and Answers Verified Solutions Latest
Update 2026/2027
Question:
FMOC Chemical Synthesis
Answer:
Used in synthesis of a growing amino acid chain to a polystyrene bead. FMOC is used as a
protecting group on the N-terminus.
Question:
Salting Out (Purification)
Answer:
Changes soluble protein to solid precipitate. Protein precipitates when the charges on the protein
match the charges in the solution.
Question:
Size-Exclusion Chromatography
Answer:
Separates sample based on size with smaller molecules eluting later.
Question:
Ion-Exchange Chromatography
Answer:
Separates sample based on charge. CM attracts +, DEAE attracts -. May have repulsion effect on
like charges. Salt or acid used to remove stuck proteins.
,Question:
Hydrophobic/Reverse Phase Chromatography
Answer:
Beads are coated with a carbon chain. Hydrophobic proteins stick better. Elute with non-H-bonding
solvent (acetonitrile).
Question:
Affinity Chromatography
Answer:
Attach a ligand that binds a protein to a bead. Elute with harsh chemicals or similar ligand.
Question:
SDS-PAGE
Answer:
Uses SDS. Gel is made from cross-linked polyacrylamide. Separates based off of mass with smaller
molecules moving faster. Visualized with Coomassie blue.
Question:
SDS
Answer:
Sodium dodecyl sulfate. Unfolds proteins and gives them uniform negative charge.
Question:
Isoelectric Focusing
Answer:
Variation of gel electrophoresis where protein charge matters. Involves electrodes and pH gradient.
Protein stops at their pI when neutral.
Question:
,FDNB (1-fluoro-2,3-dinitrobenzene)
Answer:
FDNB reacts with the N-terminus of the protein to produce a 2,4-dinitrophenol derivative that
labels the first residue. Can repeat hydrolysis to determine sequential amino acids.
Question:
DTT (dithiothreitol)
Answer:
Reduces disulfide bonds.
Question:
Iodoacetate
Answer:
Adds carboxymethyl group on free -SH groups. Blocks disulfide bonding.
Question:
Homologs
Answer:
Shares 25% identity with another gene
Question:
Orthologs
Answer:
Similar genes in different organisms
Question:
Paralogs
Answer:
, Similar "paired" genes in the same organism
Question:
Ramachandran Plot
Answer:
Shows favorable phi-psi angle combinations. 3 main "wells" for α-helices, ß-sheets, and
left-handed α-helices.
Question:
Glycine Ramachandran Plot
Answer:
Glycine can adopt more angles. (H's for R- group).
Question:
Proline Ramachandran Plot
Answer:
Proline adopts fewer angles. Amino group is incorporated into a ring.
Question:
α-helices
Answer:
Ala is common, Gly & Pro are not very common. Side-chain interactions every 3 or 4 residues.
Turns once every 3.6 residues. Distance between backbones is 5.4Å.
Question:
Helix Dipole
Answer:
Formed from added dipole moments of all hydrogen bonds in an α-helix. N-terminus is δ+ and
C-terminus is δ-.
