ACS BIOCHEMISTRY EXAM 200+ QUESTIONS WITH VERIFIED ANSWERS BY EXPERTS 2023 LATEST UPDATE.

ACS BIOCHEMISTRY EXAM 200+ QUESTIONS WITH VERIFIED ANSWERS BY EXPERTS 2023 LATEST UPDATE. 1. Henderson-Hasselbach Equation: pH = pKa + log ([A-] / [HA]) 2. FMOC Chemical Synthesis: 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): Changes soluble protein to solid precipitate. Protein precipitates when the charges on the protein match the charges in the solution. 4. Size-Exclusion Chromatography: Separates sample based on size with smaller molecules eluting later. 5. Ion-Exchange Chromatography: 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: Beads are coated with a carbon chain. Hydrophobic proteins stick better. Elute with non-H-bonding solvent (acetonitrile). 7. Affinity Chromatography: Attach a ligand that binds a protein to a bead. Elute with harsh chemicals or similar ligand. 8. SDS-PAGE: 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: Sodium dodecyl sulfate. Unfolds proteins and gives them uniform negative charge. 10. Isoelectric Focusing: 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): 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): Reduces disulfide bonds. 13. Iodoacetate: Adds carboxymethyl group on free -SH groups. Blocks disulfide bonding. 14. Homologs: Shares 25% identity with another gene 15. Orthologs: Similar genes in different organisms 16. Paralogs: Similar "paired" genes in the same organism 1 / 18 ACS BIOCHEMISTRY EXAM 17. Ramachandran Plot: Shows favorable phi-psi angle combinations. 3 main "wells" for ±-helices, ß-sheets, and left-handed ±-helices. 18. Glycine Ramachandran Plot: Glycine can adopt more angles. (H's for R-group). 19. Proline Ramachandran Plot: Proline adopts fewer angles. Amino group is incorporated into a ring. 20. ±-helices: 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: Formed from added dipole moments of all hydrogen bonds in an ±-helix. N-terminus is ´+ and C-terminus is ´-. 22. ß-sheet: Either parallel or anti-parallel. Often twisted to increase strength. 23. Anti-parallel ß-sheet: Alternating sheet directions (C & N-termini don't line-up). Has straight H-bonds. 24. Parallel ß-sheet: Same sheet directions (C & N-termini line up). Has angled H-bonds. 25. ß-turns: 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. 26. Loops: Not highly structured. Not necessary highly flexible, but can occasionally move. Very variable in sequence. 27. Circular Dichroism: Uses UV light to measure 2° structure. Can be used to measure destabilization. 28. Disulfide-bonds: Bonds between two -SH groups that form between 2° and 3° structure. 29. ß-mercaptoethanol: Breaks disulfide bonds. 30. ±-keratin: formed from 2 ±-helices twisted around each other. "Coiled coil". Cross-linked by disulfide bonds. 31. Collagen: Repeating se