BIOCHEMISTRY ACS REVIEW|VERIFIED QUESTIONS AND CORRECT DETAILED
ANSWERS|RATED AND GRADED A+ NEW UPDATE| 2026/2027
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
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
ANSWERS|RATED AND GRADED A+ NEW UPDATE| 2026/2027
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
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
