ACS Biochemistry Exam 2027 Questions and Answers | Verified
| A+
Question 1.
FMOC Chemical Synthesis
Correct 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 2.
Salting Out (Purification)
Correct Answer: Changes soluble protein to solid precipitate. Protein
precipitates when the charges on the protein match the charges in the
solution.
Question 3.
Size-Exclusion Chromatography
Correct Answer: Separates sample based on size with smaller molecules
eluting later.
Question 4.
Ion-Exchange Chromatography
Correct 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 5.
Hydrophobic/Reverse Phase Chromatography
Correct Answer: Beads are coated with a carbon chain. Hydrophobic proteins
stick better. Elute with non-H-bonding solvent (acetonitrile).
Question 6.
Affinity Chromatography
Correct Answer: Attach a ligand that binds a protein to a bead. Elute with
harsh chemicals or similar ligand.
Question 7.
SDS-PAGE
,Correct 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 8.
SDS
Correct Answer: Sodium dodecyl sulfate. Unfolds proteins and gives them
uniform negative charge.
Question 9.
Isoelectric Focusing
Correct Answer: Variation of gel electrophoresis where protein charge
matters. Involves electrodes and pH gradient. Protein stops at their pI when
neutral.
Question 10.
FDNB (1-fluoro-2,3-dinitrobenzene)
Correct 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.
• DTT (dithiothreitol) -✓✓Reduces disulfide bonds.
Question 11.
Iodoacetate
Correct Answer: Adds carboxymethyl group on free -SH groups. Blocks
disulfide bonding.
Question 12.
Homologs
Correct Answer: Shares 25% identity with another gene
Question 13.
Orthologs
Correct Answer: Similar genes in different organisms
Question 14.
Paralogs
Correct Answer: Similar "paired" genes in the same organism
,Question 15.
Ramachandran Plot
Correct Answer: Shows favorable phi-psi angle combinations. 3 main "wells"
for α-helices, ß-sheets, and left-handed α-helices.
Question 16.
Glycine Ramachandran Plot
Correct Answer: Glycine can adopt more angles. (H's for R- group).
Question 17.
Proline Ramachandran Plot
Correct Answer: Proline adopts fewer angles. Amino group is incorporated into
a ring.
Question 18.
α-helices
Correct 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 19.
Helix Dipole
Correct Answer: Formed from added dipole moments of all hydrogen bonds in
an α-helix. N-terminus is δ+ and C-terminus is δ-.
Question 20.
ß-sheet
Correct Answer: Either parallel or anti-parallel. Often twisted to increase
strength.
Question 21.
Anti-parallel ß-sheet
Correct Answer: Alternating sheet directions (C & N-termini don't line- up).
Has straight H-bonds.
Question 22.
Parallel ß-sheet
, Correct Answer: Same sheet directions (C & N-termini line up). Has angled
H-bonds.
Question 23.
ß-turns
Correct 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.
• Loops -✓✓Not highly structured. Not necessary highly flexible, but can
occasionally move. Very variable in sequence.
Question 24.
Circular Dichroism
Correct Answer: Uses UV light to measure 2° structure. Can be used to
measure destabilization.
Question 25.
Disulfide-bonds
Correct Answer: Bonds between two -SH groups that form between 2° and 3°
structure.
Question 26.
ß-mercaptoethanol
Correct Answer: Breaks disulfide bonds.
Question 27.
α-keratin
Correct Answer: formed from 2 α-helices twisted around each other. "Coiled
coil". Cross-linked by disulfide bonds.
Question 28.
Collagen
Correct Answer: Repeating sequence of Gly-X-Pro. 3 stranded "coiled coil".
Contains gly core.
Question 29.
Myoglobin 4° Structure
Correct Answer: Symmetric homodimer,
| A+
Question 1.
FMOC Chemical Synthesis
Correct 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 2.
Salting Out (Purification)
Correct Answer: Changes soluble protein to solid precipitate. Protein
precipitates when the charges on the protein match the charges in the
solution.
Question 3.
Size-Exclusion Chromatography
Correct Answer: Separates sample based on size with smaller molecules
eluting later.
Question 4.
Ion-Exchange Chromatography
Correct 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 5.
Hydrophobic/Reverse Phase Chromatography
Correct Answer: Beads are coated with a carbon chain. Hydrophobic proteins
stick better. Elute with non-H-bonding solvent (acetonitrile).
Question 6.
Affinity Chromatography
Correct Answer: Attach a ligand that binds a protein to a bead. Elute with
harsh chemicals or similar ligand.
Question 7.
SDS-PAGE
,Correct 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 8.
SDS
Correct Answer: Sodium dodecyl sulfate. Unfolds proteins and gives them
uniform negative charge.
Question 9.
Isoelectric Focusing
Correct Answer: Variation of gel electrophoresis where protein charge
matters. Involves electrodes and pH gradient. Protein stops at their pI when
neutral.
Question 10.
FDNB (1-fluoro-2,3-dinitrobenzene)
Correct 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.
• DTT (dithiothreitol) -✓✓Reduces disulfide bonds.
Question 11.
Iodoacetate
Correct Answer: Adds carboxymethyl group on free -SH groups. Blocks
disulfide bonding.
Question 12.
Homologs
Correct Answer: Shares 25% identity with another gene
Question 13.
Orthologs
Correct Answer: Similar genes in different organisms
Question 14.
Paralogs
Correct Answer: Similar "paired" genes in the same organism
,Question 15.
Ramachandran Plot
Correct Answer: Shows favorable phi-psi angle combinations. 3 main "wells"
for α-helices, ß-sheets, and left-handed α-helices.
Question 16.
Glycine Ramachandran Plot
Correct Answer: Glycine can adopt more angles. (H's for R- group).
Question 17.
Proline Ramachandran Plot
Correct Answer: Proline adopts fewer angles. Amino group is incorporated into
a ring.
Question 18.
α-helices
Correct 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 19.
Helix Dipole
Correct Answer: Formed from added dipole moments of all hydrogen bonds in
an α-helix. N-terminus is δ+ and C-terminus is δ-.
Question 20.
ß-sheet
Correct Answer: Either parallel or anti-parallel. Often twisted to increase
strength.
Question 21.
Anti-parallel ß-sheet
Correct Answer: Alternating sheet directions (C & N-termini don't line- up).
Has straight H-bonds.
Question 22.
Parallel ß-sheet
, Correct Answer: Same sheet directions (C & N-termini line up). Has angled
H-bonds.
Question 23.
ß-turns
Correct 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.
• Loops -✓✓Not highly structured. Not necessary highly flexible, but can
occasionally move. Very variable in sequence.
Question 24.
Circular Dichroism
Correct Answer: Uses UV light to measure 2° structure. Can be used to
measure destabilization.
Question 25.
Disulfide-bonds
Correct Answer: Bonds between two -SH groups that form between 2° and 3°
structure.
Question 26.
ß-mercaptoethanol
Correct Answer: Breaks disulfide bonds.
Question 27.
α-keratin
Correct Answer: formed from 2 α-helices twisted around each other. "Coiled
coil". Cross-linked by disulfide bonds.
Question 28.
Collagen
Correct Answer: Repeating sequence of Gly-X-Pro. 3 stranded "coiled coil".
Contains gly core.
Question 29.
Myoglobin 4° Structure
Correct Answer: Symmetric homodimer,
