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ACS BIOCHEMISTRY EXAM QUESTIONS AND ANSWERS
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ACS BIOCHEMISTRY EXAM QUESTIONS AND ANSWERS 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 (Purificatio...

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  • October 15, 2024
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  • 2024/2025
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EMILLECT 2024/2025 ACADEMIC YEAR ©2024 EMILLECT. ALL RIGHTS RESERVED. FIRST PUBLISH OCTOBER 2024.




ACS BIOCHEMISTRY EXAM
QUESTIONS AND ANSWERS

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.




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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).


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, EMILLECT 2024/2025 ACADEMIC YEAR ©2024 EMILLECT. ALL RIGHTS RESERVED. FIRST PUBLISH OCTOBER 2024.



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.
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