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ACS BIOCHEMISTRY EXAM 2022 WITH LATEST QUESTIONS AND ANSWERS
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ACS BIOCHEMISTRY EXAM 2022 WITH LATEST QUESTIONSAND ANSWERS
Henderson-Hasselbach Equation - answerpH = pKa + log ([A-] / [HA])
FMOC Chemical Synthesis - answerUsed 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) - answerChanges soluble protein to solid precipitate. Protein
precipitates when the charges on the protein match the charges in the solution.
Size-Exclusion Chromatography - answerSeparates sample based on size with smaller molecules
eluting later.
Ion-Exchange Chromatography - answerSeparates 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 - answerBeads are coated with a carbon chain.
Hydrophobic proteins stick better. Elute with non-H-bonding solvent (acetonitrile).
Affinity Chromatography - answerAttach a ligand that binds a protein to a bead. Elute with harsh
chemicals or similar ligand.
SDS-PAGE - answerUses SDS. Gel is made from cross-linked polyacrylamide. Separates based off
of mass with smaller molecules moving faster. Visualized with Coomassie blue.
SDS - answerSodium dodecyl sulfate. Unfolds proteins and gives them uniform negative charge.
Isoelectric Focusing - answerVariation 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) - answerFDNB 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) - answerReduces disulfide bonds.
Iodoacetate - answerAdds carboxymethyl group on free -SH groups. Blocks disulfide bonding.
Homologs - answerShares 25% identity with another gene
Orthologs - answerSimilar genes in different organisms
Paralogs - answerSimilar "paired" genes in the same organism
Ramachandran Plot - answerShows favorable phi-psi angle combinations. 3 main "wells" for
α-helices, ß-sheets, and left-handed α-helices.
Glycine Ramachandran Plot - answerGlycine can adopt more angles. (H's for R-group).
Proline Ramachandran Plot - answerProline adopts fewer angles. Amino group is incorporated
into a ring.
α-helices - answerAla 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 - answerFormed from added dipole moments of all hydrogen bonds in an α-helix.
, N-terminus is δ+ and C-terminus is δ-.
ß-sheet - answerEither parallel or anti-parallel. Often twisted to increase strength.
Anti-parallel ß-sheet - answerAlternating sheet directions (C & N-termini don't line-up). Has
straight H-bonds.
Parallel ß-sheet - answerSame sheet directions (C & N-termini line up). Has angled H-bonds.
ß-turns - answerTight 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 - answerNot highly structured. Not necessary highly flexible, but can occasionally move.
Very variable in sequence.
Circular Dichroism - answerUses UV light to measure 2° structure. Can be used to measure
destabilization.
Disulfide-bonds - answerBonds between two -SH groups that form between 2° and 3° structure.
ß-mercaptoethanol - answerBreaks disulfide bonds.
α-keratin - answerformed from 2 α-helices twisted around each other. "Coiled coil". Cross-linked
by disulfide bonds.
Collagen - answerRepeating sequence of Gly-X-Pro. 3 stranded "coiled coil". Contains gly core.
Myoglobin 4° Structure - answerSymmetric homodimer,
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