ACS BIOCHEMISTRY EXAM 2026 with Practice test
and Study Guide Questions with Verified Answers for
High Yield Exam Graded A+
Henderson-Hasselbach Equation - ............ANSWER..........pH = pKa +
log ([A-] / [HA])
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.
Salting Out (Purification) - ............ANSWER..........Changes soluble
protein to solid precipitate. Protein precipitates when the charges on the
protein match the charges in the solution.
Size-Exclusion Chromatography - ............ANSWER..........Separates
sample based on size with smaller molecules eluting later.
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.
Hydrophobic/Reverse Phase Chromatography
- ............ANSWER..........Beads are coated with a carbon chain.
Hydrophobic proteins stick better. Elute with non-H-bonding solvent
(acetonitrile).
,Affinity Chromatography - ............ANSWER..........Attach a ligand that
binds a protein to a bead. Elute with harsh chemicals or similar ligand.
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.
SDS - ............ANSWER..........Sodium dodecyl sulfate. Unfolds proteins
and gives them uniform negative charge.
Isoelectric Focusing - ............ANSWER..........Variation of gel
electrophoresis where protein charge matters. Involves electrodes and pH
gradient. Protein stops at their pI when neutral.
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.
DTT (dithiothreitol) - ............ANSWER..........Reduces disulfide bonds.
Iodoacetate - ............ANSWER..........Adds carboxymethyl group on free
-SH groups. Blocks disulfide bonding.
Homologs - ............ANSWER..........Shares 25% identity with another
gene
Orthologs - ............ANSWER..........Similar genes in different organisms
,Paralogs - ............ANSWER..........Similar "paired" genes in the same
organism
Ramachandran Plot - ............ANSWER..........Shows favorable phi-psi
angle combinations. 3 main "wells" for α-helices, ß-sheets, and left-
handed α-helices.
Glycine Ramachandran Plot - ............ANSWER..........Glycine can adopt
more angles. (H's for R-group).
Proline Ramachandran Plot - ............ANSWER..........Proline adopts
fewer angles. Amino group is incorporated into a ring.
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.
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-.
ß-sheet - ............ANSWER..........Either parallel or anti-parallel. Often
twisted to increase strength.
Anti-parallel ß-sheet - ............ANSWER..........Alternating sheet
directions (C & N-termini don't line-up). Has straight H-bonds.
, Parallel ß-sheet - ............ANSWER..........Same sheet directions (C & N-
termini line up). Has angled H-bonds.
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.
Loops - ............ANSWER..........Not highly structured. Not necessary
highly flexible, but can occasionally move. Very variable in sequence.
Circular Dichroism - ............ANSWER..........Uses UV light to measure
2° structure. Can be used to measure destabilization.
Disulfide-bonds - ............ANSWER..........Bonds between two -SH
groups that form between 2° and 3° structure.
ß-mercaptoethanol - ............ANSWER..........Breaks disulfide bonds.
α-keratin - ............ANSWER..........formed from 2 α-helices twisted
around each other. "Coiled coil". Cross-linked by disulfide bonds.
Collagen - ............ANSWER..........Repeating sequence of Gly-X-Pro. 3
stranded "coiled coil". Contains gly core.
Myoglobin 4° Structure - ............ANSWER..........Symmetric homodimer,
Hemoglobin 4° Structure - ............ANSWER..........Tetramer. Dimer of
dimers. α2ß2 tetramer.
and Study Guide Questions with Verified Answers for
High Yield Exam Graded A+
Henderson-Hasselbach Equation - ............ANSWER..........pH = pKa +
log ([A-] / [HA])
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.
Salting Out (Purification) - ............ANSWER..........Changes soluble
protein to solid precipitate. Protein precipitates when the charges on the
protein match the charges in the solution.
Size-Exclusion Chromatography - ............ANSWER..........Separates
sample based on size with smaller molecules eluting later.
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.
Hydrophobic/Reverse Phase Chromatography
- ............ANSWER..........Beads are coated with a carbon chain.
Hydrophobic proteins stick better. Elute with non-H-bonding solvent
(acetonitrile).
,Affinity Chromatography - ............ANSWER..........Attach a ligand that
binds a protein to a bead. Elute with harsh chemicals or similar ligand.
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.
SDS - ............ANSWER..........Sodium dodecyl sulfate. Unfolds proteins
and gives them uniform negative charge.
Isoelectric Focusing - ............ANSWER..........Variation of gel
electrophoresis where protein charge matters. Involves electrodes and pH
gradient. Protein stops at their pI when neutral.
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.
DTT (dithiothreitol) - ............ANSWER..........Reduces disulfide bonds.
Iodoacetate - ............ANSWER..........Adds carboxymethyl group on free
-SH groups. Blocks disulfide bonding.
Homologs - ............ANSWER..........Shares 25% identity with another
gene
Orthologs - ............ANSWER..........Similar genes in different organisms
,Paralogs - ............ANSWER..........Similar "paired" genes in the same
organism
Ramachandran Plot - ............ANSWER..........Shows favorable phi-psi
angle combinations. 3 main "wells" for α-helices, ß-sheets, and left-
handed α-helices.
Glycine Ramachandran Plot - ............ANSWER..........Glycine can adopt
more angles. (H's for R-group).
Proline Ramachandran Plot - ............ANSWER..........Proline adopts
fewer angles. Amino group is incorporated into a ring.
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.
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-.
ß-sheet - ............ANSWER..........Either parallel or anti-parallel. Often
twisted to increase strength.
Anti-parallel ß-sheet - ............ANSWER..........Alternating sheet
directions (C & N-termini don't line-up). Has straight H-bonds.
, Parallel ß-sheet - ............ANSWER..........Same sheet directions (C & N-
termini line up). Has angled H-bonds.
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.
Loops - ............ANSWER..........Not highly structured. Not necessary
highly flexible, but can occasionally move. Very variable in sequence.
Circular Dichroism - ............ANSWER..........Uses UV light to measure
2° structure. Can be used to measure destabilization.
Disulfide-bonds - ............ANSWER..........Bonds between two -SH
groups that form between 2° and 3° structure.
ß-mercaptoethanol - ............ANSWER..........Breaks disulfide bonds.
α-keratin - ............ANSWER..........formed from 2 α-helices twisted
around each other. "Coiled coil". Cross-linked by disulfide bonds.
Collagen - ............ANSWER..........Repeating sequence of Gly-X-Pro. 3
stranded "coiled coil". Contains gly core.
Myoglobin 4° Structure - ............ANSWER..........Symmetric homodimer,
Hemoglobin 4° Structure - ............ANSWER..........Tetramer. Dimer of
dimers. α2ß2 tetramer.
