Biochem ACS Review Exam Questions And
Answers (Guaranteed A+)
What amino acids have nonpolar, aliphatic R groups? - answer✔Glycine, Alanine, Proline,
Valine, Leucine, Isoleucine, Methionine
What amino acids have polar, uncharged R groups? - answer✔Serine, Threonine, Cysteine,
Asparagine, and Glutamine
What amino acids have aromatic R groups? - answer✔Phenylalanine, Tyrosine, and Tryptophan
What amino acids have negatively charged R groups? - answer✔Aspartate and Glutamate
What amino acids have positively charged R groups? - answer✔Lysine, Arginine, and Histidine
What is isoelectric focusing? - answer✔Proteins are electrophoresed in a pH gradient gel. Each
protein will move in the gel as long as the protein contains a charge
What does SDS do? - answer✔It binds to proteins and denatures it. All proteins have same
mass/ charge ratio
How do you determine the Amino Terminus? - answer✔1. Make a derivative of the N-terminus
with a marker molecule
2. Hydrolyze the peptide
3. N-terminal AA is identified by chromatography- modified amino acid will elute differently
than unmodified AA
What molecule does Edman Degradation use? - answer✔Phenyl Isothiocyanate (PTH)
What does Edman Degradation do? - answer✔It removes one amino acid at a time. The limit is
50 amino acids. After 50 amino acids, the polypeptide must be hydrolyzed into smaller fractions
Where does Cyanogen Bromide cleave? - answer✔Cleaves only on the caryboxyl side of
Methionine residues
Where does Trypsin cleave? - answer✔Trypsin cleaves on the carboxyl side of positive residues
such as Arginine and Lysine
ALL RIGHTS RESERVED.
What happens in Disulfide Position? - answer✔It is a diagonal electrophoresis.
The peptides are cleaved without destroying the disulfide bonds and then exposed to performic
acid vapors.
The performic acid vapors convert any S-X bond to a SO3-.
These fragments will be off the diagonal
In Peptide Synthesis, what is the protecting group? - answer✔Fmoc
What is the group that activates amino acid 2? - answer✔DCC- Dicyclohexylcarbodiimide
What acts as the nucleophile in Peptide Synthesis? - answer✔Amino acid 1 that is connected to
the polystyrene bead.
What causes the polystyrene bead to disconnect from amino acid 1? - answer✔HF
In what order does peptide synthesis, synthesize amino acids? - answer✔Carboxy end to the
amine end
In what order does the body synthesize amino acids? - answer✔Amino terminus to carboxy
terminus
What are the hydrogen bonds in Alpha Helix? - answer✔The carboxyl group is hydrogen
bonded with the Hydrogen on the Nitrogen 4 residues away. Alpha helix is clockwise, or right
handed
Which Beta Pleated sheet is more stable, parallel or antiparallel? - answer✔Antiparallel,
because there is a direct overlap of electrons which creates more stability
What does B-mercaptoethanol do? - answer✔It breaks disulfide bonds
What does Urea do? - answer✔It interrupts hydrogen bonds
What is Levinthal's Paradox? - answer✔It is the difference between the calculated time for a
protein to fold and the real time it take for a protein to fold.
The discrepancy in time is answered by what? - answer✔Progressive stabilization
What is Progressive stabilization? - answer✔It is the stabilization of intermediates that
resemble parts of the final folded state
What is the molten globule state? - answer✔It is the state between random coil and native
state. It contains much secondary structure.
How is the molten globule formed? - answer✔It is formed by hydrophobic collapse.
Hydrophobic residues are sequestered toward the inside of a protein
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