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ACS BIOCHEMISTRY EXAM Questions Answers Graded A 100 VERIFIED Latest Update 2023 $14.99   Add to cart

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ACS BIOCHEMISTRY EXAM Questions Answers Graded A 100 VERIFIED Latest Update 2023

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ACS BIOCHEMISTRY EXAM | Questions & Answers (Graded A+) |100% VERIFIED Latest Update 2023 Henderson-Hasselbach Equation FMOC Chemical Synthesis Salting Out (Purification) Size-Exclusion Chromatography Ion-Exchange Chromatography Hydrophobic/Reverse Phase Chromatography Affinity Chromatograph...

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  • March 12, 2024
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ACS BIOCHEMISTRY EXAM | Questions &
Answers (Graded A+) |100% VERIFIED Latest
Update 2023

1). Henderson-hasselbach equation

 Ans: pH = pKa + log ([A-] / [HA])


2). Fmoc chemical synthesis

 Ans: Used in synthesis of a growing amino acid chain to a polystyrene bead. FMOC is
used as a protecting group on the N-terminus.


3). Salting out (purification)

 Ans: Changes soluble protein to solid precipitate. Protein precipitates when the
charges on the protein match the charges in the solution.


4). Size-exclusion chromatography

 Ans: Separates sample based on size with smaller molecules eluting later.


5). Ion-exchange chromatography

 Ans: Separates sample based on charge. CM attracts +, DEAE attracts -. May have
repulsion effect on like charges. Salt or acid used to remove stuck proteins.


6). Hydrophobic/reverse phase chromatography

 Ans: Beads are coated with a carbon chain. Hydrophobic proteins stick better. Elute
with non-H-bonding solvent (acetonitrile).


7). Affinity chromatography

 Ans: Attach a ligand that binds a protein to a bead. Elute with harsh chemicals or
similar ligand.




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, 8). Sds-page

 Ans: Uses SDS. Gel is made from cross-linked polyacrylamide. Separates based off of
mass with smaller molecules moving faster. Visualized with Coomassie blue.


9). Sds

 Ans: Sodium dodecyl sulfate. Unfolds proteins and gives them uniform negative
charge.


10). Isoelectric focusing

 Ans: Variation of gel electrophoresis where protein charge matters. Involves
electrodes and pH gradient. Protein stops at their pI when neutral.


11). 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.


12). Dtt (dithiothreitol)

 Ans: Reduces disulfide bonds.


13). Iodoacetate

 Ans: Adds carboxymethyl group on free -SH groups. Blocks disulfide bonding.


14). Homologs

 Ans: Shares 25% identity with another gene


15). Orthologs

 Ans: Similar genes in different organisms


16). Paralogs

 Ans: Similar "paired" genes in the same organism




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, 17). Ramachandran plot

 Ans: Shows favorable phi-psi angle combinations. 3 main "wells" for α-helices, ß-
sheets, and left-handed α-helices.


18). Glycine ramachandran plot

 Ans: Glycine can adopt more angles. (H's for R-group).


19). Proline ramachandran plot

 Ans: Proline adopts fewer angles. Amino group is incorporated into a ring.


20). 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.


21). 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-.


22). Ss-sheet

 Ans: Either parallel or anti-parallel. Often twisted to increase strength.


23). Anti-parallel ß-sheet

 Ans: Alternating sheet directions (C & N-termini don't line-up). Has straight H-bonds.


24). Parallel ß-sheet

 Ans: Same sheet directions (C & N-termini line up). Has angled H-bonds.


25). 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.




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, 26). Loops

 Ans: Not highly structured. Not necessary highly flexible, but can occasionally move.
Very variable in sequence.


27). Circular dichroism

 Ans: Uses UV light to measure 2° structure. Can be used to measure destabilization.


28). Disulfide-bonds

 Ans: Bonds between two -SH groups that form between 2° and 3° structure.


29). Ss-mercaptoethanol

 Ans: Breaks disulfide bonds.


30). Α-keratin

 Ans: formed from 2 α-helices twisted around each other. "Coiled coil". Cross-linked by
disulfide bonds.


31). Collagen

 Ans: Repeating sequence of Gly-X-Pro. 3 stranded "coiled coil". Contains gly core.


32). Myoglobin 4° structure

 Ans: Symmetric homodimer,


33). Hemoglobin 4° structure

 Ans: Tetramer. Dimer of dimers. α2ß2 tetramer.


34). Α/ß protein folding

 Ans: Less distinct areas of α and ß folding.


35). Α+ß protein folding




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