ACS Biochemistry Exam 2027 Questions and Answers | Verified | A+

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,