ACS BIOCHEMISTRY EXAM | Questions with 100% Verified
Answers | Latest Update 2026/2027
Question: Henderson-Hasselbach Equation
Answer: pH = pKa + log ([A-] / [HA])
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-.
, Question: ß-sheet
Answer: Either parallel or anti-parallel. Often twisted to increase strength.
Question: Anti-parallel ß-sheet
Answer: Alternating sheet directions (C & N-termini don't line-up). Has straight H-bonds.
Question: Parallel ß-sheet
Answer: Same sheet directions (C & N-termini line up). Has angled H-bonds.
Question: ß-turns
Answer: Tight u-turns with specific phi-psi angles. Must have gly at position 3. Proline may also
be
at ß-turn because it can have a cis-omega angle.
Question: Loops
Answer: Not highly structured. Not necessary highly flexible, but can occasionally move. Very
variable in sequence.
Question: Circular Dichroism
Answer: Uses UV light to measure 2° structure. Can be used to measure destabilization.
Question: Disulfide-bonds
Answer: Bonds between two -SH groups that form between 2° and 3° structure.
Question: ß-mercaptoethanol
Answer: Breaks disulfide bonds.
Question: α-keratin
Answer: formed from 2 α-helices twisted around each other. "Coiled coil". Cross-linked by
disulfide bonds.
Question: Collagen
Answer: Repeating sequence of Gly-X-Pro. 3 stranded "coiled coil". Contains gly core.
Question: Myoglobin 4° Structure
Answer: Symmetric homodimer,
Question: Hemoglobin 4° Structure
Answer: Tetramer. Dimer of dimers. α2ß2 tetramer.
Answers | Latest Update 2026/2027
Question: Henderson-Hasselbach Equation
Answer: pH = pKa + log ([A-] / [HA])
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-.
, Question: ß-sheet
Answer: Either parallel or anti-parallel. Often twisted to increase strength.
Question: Anti-parallel ß-sheet
Answer: Alternating sheet directions (C & N-termini don't line-up). Has straight H-bonds.
Question: Parallel ß-sheet
Answer: Same sheet directions (C & N-termini line up). Has angled H-bonds.
Question: ß-turns
Answer: Tight u-turns with specific phi-psi angles. Must have gly at position 3. Proline may also
be
at ß-turn because it can have a cis-omega angle.
Question: Loops
Answer: Not highly structured. Not necessary highly flexible, but can occasionally move. Very
variable in sequence.
Question: Circular Dichroism
Answer: Uses UV light to measure 2° structure. Can be used to measure destabilization.
Question: Disulfide-bonds
Answer: Bonds between two -SH groups that form between 2° and 3° structure.
Question: ß-mercaptoethanol
Answer: Breaks disulfide bonds.
Question: α-keratin
Answer: formed from 2 α-helices twisted around each other. "Coiled coil". Cross-linked by
disulfide bonds.
Question: Collagen
Answer: Repeating sequence of Gly-X-Pro. 3 stranded "coiled coil". Contains gly core.
Question: Myoglobin 4° Structure
Answer: Symmetric homodimer,
Question: Hemoglobin 4° Structure
Answer: Tetramer. Dimer of dimers. α2ß2 tetramer.
