ACS BIOCHEMISTRY EXAM Questions With Complete Solution Henderson-Hasselbach Equation - Correct Answers ✅pH = pKa + log ([A-] / [HA]) FMOC Chemical Synthesis - Correct Answers ✅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) - Correct Answers ✅Changes soluble protein to solid precipitate. Protein precipitates when the charges on the protein match the charges in the solution.Size-Exclusion Chromatography - Correct Answers ✅Separates sample based on size with smaller molecules eluting later.Ion-Exchange Chromatography - Correct Answers ✅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 - Correct Answers ✅Beads are coated with a carbon chain.Hydrophobic proteins stick better. Elute with non-H-bonding solvent (acetonitrile). 1 / 4
ACS BIOCHEMISTRY EXAM Questions With Complete Solution Affinity Chromatography - Correct Answers ✅Attach a ligand that binds a protein to a bead. Elute with harsh chemicals or similar ligand.SDS-PAGE - Correct Answers ✅Uses SDS. Gel is made from cross-linked polyacrylamide. Separates based off of mass with smaller molecules moving faster. Visualized with Coomassie blue.SDS - Correct Answers ✅Sodium dodecyl sulfate. Unfolds proteins and gives them uniform negative charge.Isoelectric Focusing - Correct Answers ✅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) - Correct Answers ✅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) - Correct Answers ✅Reduces disulfide bonds.Iodoacetate - Correct Answers ✅Adds carboxymethyl group on free -SH groups. Blocks disulfide bonding. 2 / 4
ACS BIOCHEMISTRY EXAM Questions With Complete Solution Homologs - Correct Answers ✅Shares 25% identity with another gene Orthologs - Correct Answers ✅Similar genes in different organisms Paralogs - Correct Answers ✅Similar "paired" genes in the same organism Ramachandran Plot - Correct Answers ✅Shows favorable phi-psi angle combinations. 3 main "wells" for α-helices, ß- sheets, and left-handed α-helices.Glycine Ramachandran Plot - Correct Answers ✅Glycine can adopt more angles. (H's for R-group).Proline Ramachandran Plot - Correct Answers ✅Proline adopts fewer angles. Amino group is incorporated into a ring.α-helices - Correct Answers ✅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. 3 / 4
ACS BIOCHEMISTRY EXAM Questions With Complete Solution Helix Dipole - Correct Answers ✅Formed from added dipole moments of all hydrogen bonds in an α-helix. N-terminus is δ+ and C-terminus is δ-.ß-sheet - Correct Answers ✅Either parallel or anti-parallel.Often twisted to increase strength.Anti-parallel ß-sheet - Correct Answers ✅Alternating sheet directions (C & N-termini don't line-up). Has straight H-bonds.Parallel ß-sheet - Correct Answers ✅Same sheet directions (C & N-termini line up). Has angled H-bonds.ß-turns - Correct Answers ✅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 - Correct Answers ✅Not highly structured. Not necessary highly flexible, but can occasionally move. Very variable in sequence.Circular Dichroism - Correct Answers ✅Uses UV light to measure 2° structure. Can be used to measure destabilization.
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