Exam (elaborations)
ACS BIOCHEMISTRY EXAM QUESTIONS AND ANSWERS 100% SOLVED
- Course
- Institution
ACS BIOCHEMISTRY EXAM
[Show more]
Content preview
ACS BIOCHEMISTRY EXAMHenderson-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,
Hemoglobin 4° Structure - answerTetramer. Dimer of dimers. α2ß2 tetramer.
α/ß Protein Folding - answerLess distinct areas of α and ß folding.
α+ß Protein Folding - answerTwo distinct areas of α and ß folding.
Mechanism of Denaturants - answerHighly soluble, H-binding molecules. Stabilize
protein backbone in water. Allows denatured state to be stabilized.
Temperature Denaturation of Protein - answerMidpoint of reaction is Tm.
Cooperative Protein Folding - answerFolding transition is sharp. More reversible.
Folding Funnel - answerShows 3D version of 2D energy states. Lowest energy is stable
protein. Rough funnel is less cooperative.
Protein-Protein Interfaces - answer"Core" and "fringe" of the interfaces. Core is more
hydrophobic and is on the inside when interfaced. Fringe is more hydrophilic.
π-π Ring Stacking - answerWeird interaction where aromatic rings stack on each other
in positive interaction.
σ-hole - answerMethyl group has area of diminished electron density in center; attracts
electronegative groups
Fe Binding of O2 - answerFe2+ binds to O2 reversible. Fe3+ has an additional + charge
and binds to O2 irreversibly. Fe3+ rusts in O2 rich environments.
Ka for Binding - answerKa = [PL] / [P][L]
ϴ-value in Binding - answerϴ = (bound / total)x100%
ϴ = [L] / ([L] + 1/Ka)
Kd for binding - answerKd = [L] when 50% bound to protein.
Kd = 1/Ka
High-Spin Fe - answerElectrons are "spread out" and result in larger atom.
Low-Spin Fe - answerElectrons are less "spread out" and are compacted by electron
rich porphyrin ring.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller julianah420. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $13.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
81113 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now