ACS BIOCHEMISTRY ACTUAL
CERTIFICATION PAPER 2026 QUESTIONS
WITH ANSWERS FULL SOLUTION.
■ SDS. Ans: Sodium dodecyl sulfate. Unfolds proteins and gives them
uniform negative charge.
■ Isoelectric Focusing. Ans: 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). Ans: 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). Ans: Reduces disulfide bonds.
■ Iodoacetate. Ans: Adds carboxymethyl group on free -SH groups.
Blocks disulfide bonding.
■ Homologs. Ans: Shares 25% identity with another gene
,■ Orthologs. Ans: Similar genes in different organisms
■ Paralogs. Ans: Similar "paired" genes in the same organism
■ Ramachandran Plot. Ans: Shows favorable phi-psi angle
combinations. 3 main "wells" for α-helices, ß-sheets, and left-handed α-
helices.
■ Glycine Ramachandran Plot. Ans: Glycine can adopt more angles. (H's
for R-group).
■ Proline Ramachandran Plot. Ans: Proline adopts fewer angles. Amino
group is incorporated into a ring.
■ α-helices. Ans: 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. Ans: Formed from added dipole moments of all
hydrogen bonds in an α-helix. N-terminus is δ+ and C-terminus is δ-.
■ ß-sheet. Ans: Either parallel or anti-parallel. Often twisted to increase
strength.
,■ Anti-parallel ß-sheet. Ans: Alternating sheet directions (C & N-termini
don't line-up). Has straight H-bonds.
■ Parallel ß-sheet. Ans: Same sheet directions (C & N-termini line up).
Has angled H-bonds.
■ ß-turns. Ans: 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. Ans: Not highly structured. Not necessary highly flexible, but
can occasionally move. Very variable in sequence.
■ Circular Dichroism. Ans: Uses UV light to measure 2° structure. Can
be used to measure destabilization.
■ Disulfide-bonds. Ans: Bonds between two -SH groups that form
between 2° and 3° structure.
■ ß-mercaptoethanol. Ans: Breaks disulfide bonds.
■ α-keratin. Ans: formed from 2 α-helices twisted around each other.
"Coiled coil". Cross-linked by disulfide bonds.
, ■ Collagen. Ans: Repeating sequence of Gly-X-Pro. 3 stranded "coiled
coil". Contains gly core.
■ Myoglobin 4° Structure. Ans: Symmetric homodimer,
■ Hemoglobin 4° Structure. Ans: Tetramer. Dimer of dimers. α2ß2
tetramer.
■ α/ß Protein Folding. Ans: Less distinct areas of α and ß folding.
■ α+ß Protein Folding. Ans: Two distinct areas of α and ß folding.
■ Mechanism of Denaturants. Ans: Highly soluble, H-binding
molecules. Stabilize protein backbone in water. Allows denatured state
to be stabilized.
■ Temperature Denaturation of Protein. Ans: Midpoint of reaction is Tm.
■ Cooperative Protein Folding. Ans: Folding transition is sharp. More
reversible.
■ Folding Funnel. Ans: Shows 3D version of 2D energy states. Lowest
energy is stable protein. Rough funnel is less cooperative.
CERTIFICATION PAPER 2026 QUESTIONS
WITH ANSWERS FULL SOLUTION.
■ SDS. Ans: Sodium dodecyl sulfate. Unfolds proteins and gives them
uniform negative charge.
■ Isoelectric Focusing. Ans: 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). Ans: 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). Ans: Reduces disulfide bonds.
■ Iodoacetate. Ans: Adds carboxymethyl group on free -SH groups.
Blocks disulfide bonding.
■ Homologs. Ans: Shares 25% identity with another gene
,■ Orthologs. Ans: Similar genes in different organisms
■ Paralogs. Ans: Similar "paired" genes in the same organism
■ Ramachandran Plot. Ans: Shows favorable phi-psi angle
combinations. 3 main "wells" for α-helices, ß-sheets, and left-handed α-
helices.
■ Glycine Ramachandran Plot. Ans: Glycine can adopt more angles. (H's
for R-group).
■ Proline Ramachandran Plot. Ans: Proline adopts fewer angles. Amino
group is incorporated into a ring.
■ α-helices. Ans: 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. Ans: Formed from added dipole moments of all
hydrogen bonds in an α-helix. N-terminus is δ+ and C-terminus is δ-.
■ ß-sheet. Ans: Either parallel or anti-parallel. Often twisted to increase
strength.
,■ Anti-parallel ß-sheet. Ans: Alternating sheet directions (C & N-termini
don't line-up). Has straight H-bonds.
■ Parallel ß-sheet. Ans: Same sheet directions (C & N-termini line up).
Has angled H-bonds.
■ ß-turns. Ans: 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. Ans: Not highly structured. Not necessary highly flexible, but
can occasionally move. Very variable in sequence.
■ Circular Dichroism. Ans: Uses UV light to measure 2° structure. Can
be used to measure destabilization.
■ Disulfide-bonds. Ans: Bonds between two -SH groups that form
between 2° and 3° structure.
■ ß-mercaptoethanol. Ans: Breaks disulfide bonds.
■ α-keratin. Ans: formed from 2 α-helices twisted around each other.
"Coiled coil". Cross-linked by disulfide bonds.
, ■ Collagen. Ans: Repeating sequence of Gly-X-Pro. 3 stranded "coiled
coil". Contains gly core.
■ Myoglobin 4° Structure. Ans: Symmetric homodimer,
■ Hemoglobin 4° Structure. Ans: Tetramer. Dimer of dimers. α2ß2
tetramer.
■ α/ß Protein Folding. Ans: Less distinct areas of α and ß folding.
■ α+ß Protein Folding. Ans: Two distinct areas of α and ß folding.
■ Mechanism of Denaturants. Ans: Highly soluble, H-binding
molecules. Stabilize protein backbone in water. Allows denatured state
to be stabilized.
■ Temperature Denaturation of Protein. Ans: Midpoint of reaction is Tm.
■ Cooperative Protein Folding. Ans: Folding transition is sharp. More
reversible.
■ Folding Funnel. Ans: Shows 3D version of 2D energy states. Lowest
energy is stable protein. Rough funnel is less cooperative.
