Hydrolysis + Protein Assays

The process that completely breaks down proteins into free amino acids using a strong acid or base at high temperature is known as _.
A) Partial Hydrolysis
B) Complete Hydrolysis
C) Enzymatic Hydrolysis
D) Catalytic Cleavage

Correct answer: B

The reagent commonly used in acid hydrolysis of proteins is _.
A) 4M NaOH
B) 6M HCl
C) Phosphate buffer pH 7.5
D) Potassium sodium tartrate

Correct answer: B

Which amino acid is completely destroyed during acid hydrolysis with 6M HCl?
A) Tyrosine
B) Cysteine
C) Tryptophan
D) Valine

Correct answer: C

In acid hydrolysis, which amino acids are converted into their acidic forms Asp and Glu?
A) Serine and Threonine
B) Asparagine and Glutamine
C) Valine and Isoleucine
D) Arginine and Lysine

Correct answer: B

An advantage of alkaline hydrolysis over acid hydrolysis is that _.
A) Tryptophan is preserved
B) Arginine is stabilized
C) Asparagine is protected
D) Tyrosine is enhanced

Correct answer: A

Which amino acids are destroyed during alkaline hydrolysis?
A) Cys, Tyr, Trp
B) Arg, Asn, Gln, Ser
C) Val, Ile, Thr
D) Gly, Ala, Met

Correct answer: B

In enzymatic hydrolysis, the catalyst used to partially break peptide bonds is a(n) _.
A) Acid
B) Base
C) Proteolytic enzyme
D) Salt

Correct answer: C

Which of the following enzymes cleaves peptide bonds at the C-terminal side of arginine (R) or lysine (K)?
A) Trypsin
B) Chymotrypsin
C) Papain
D) Aminopeptidase

Correct answer: A

The enzyme that hydrolyzes peptide bonds at the C-terminal side of aromatic amino acids (F, Y, W) is _.
A) Trypsin
B) Carboxypeptidase A
C) Chymotrypsin
D) Papain

Correct answer: C

Which enzyme removes amino acids from the N-terminal end of a peptide chain?
A) Carboxypeptidase A
B) Aminopeptidase
C) Carboxypeptidase B
D) Trypsin

Correct answer: B

An advantage of enzymatic hydrolysis over chemical hydrolysis is that _.
A) It requires extreme pH
B) Amino acids remain intact
C) It produces only amino acids
D) It destroys peptide bonds completely

Correct answer: B

The reagent used in the Bradford Assay is _.
A) Biuret Reagent
B) Coomassie Brilliant Blue G-250
C) Sodium Dodecyl Sulfate
D) Ninhydrin

Correct answer: B

Coomassie Brilliant Blue G-250 changes from brown (465 nm) to blue (595 nm) when _.
A) Dissolved in ethanol
B) Mixed with acid
C) It binds to protein
D) Exposed to UV light

Correct answer: C

The basic amino acids responsible for the electrostatic binding in the Bradford Assay are _.
A) Asp, Glu, and Ser
B) His, Arg, and Lys
C) Val, Ile, and Leu
D) Trp, Tyr, and Phe

Correct answer: B

Which aromatic amino acids stabilize the hydrophobic core of the dye in the Bradford Assay?
A) His and Lys
B) Arg and Gln
C) Trp and Phe
D) Gly and Ala

Correct answer: C

Which of the following is NOT an advantage of the Bradford Assay?
A) High sensitivity (~5 μg/mL)
B) Compatible with buffers and salts
C) Rapid and simple
D) Independent of protein composition

Correct answer: D

The Biuret Assay detects the presence of _.
A) Aromatic rings
B) Peptide bonds
C) Sulfhydryl groups
D) Free amino acids

Correct answer: B

The Biuret Reagent contains NaOH, CuSO₄, and _.
A) Ethanol
B) Potassium sodium tartrate
C) Ammonium chloride
D) Hydrochloric acid

Correct answer: B

A disadvantage of the Biuret Assay is that _.
A) It is too sensitive for low protein samples
B) It requires very expensive reagents
C) It interferes with phosphate buffers
D) It cannot detect aromatic residues

Correct answer: A

In the Biuret test, the violet-colored complex forms when _.
A) Cu(II) is reduced to Cu(I) and binds to peptide nitrogens
B) Cu(I) oxidizes peptide nitrogens
C) Peptide bonds are broken
D) Urea reacts with the base

Correct answer: A

In the Bradford assay, Coomassie Brilliant Blue G-250 exists as a cationic (brown) form in _.
A) Basic solution
B) Acidic solution
C) Neutral buffer
D) Organic solvent

Correct answer: B

The color change from brown (465 nm) to blue (595 nm) in the Bradford assay indicates _.
A) Protein hydrolysis
B) Protein-dye complex formation
C) pH neutralization
D) Dye precipitation

Correct answer: B

In the Bradford assay, the sulfonic acid group of the dye interacts primarily with which residues of the protein?
A) Acidic amino acids
B) Basic amino acids
C) Aromatic amino acids
D) Non-polar amino acids

Correct answer: B

The hydrophobic core of Coomassie dye is stabilized by interactions with which amino acid residues?
A) Tryptophan and Phenylalanine
B) Lysine and Arginine
C) Glycine and Alanine
D) Serine and Threonine

Correct answer: A

Which of the following is a limitation of the Bradford Assay?
A) It requires long incubation times
B) Its sensitivity is too low for dilute protein samples
C) It depends on protein composition and basic amino acid content
D) It is affected by detergent interference

Correct answer: C

The Biuret reaction produces a violet complex due to the coordination of copper ions with _.
A) Aromatic rings
B) Peptide bonds
C) Thiol groups
D) Amino groups

Correct answer: B

Potassium sodium tartrate is added to the Biuret reagent to _.
A) Stabilize Cu²⁺ ions
B) Precipitate peptides
C) Oxidize amino acids
D) Adjust the pH of the solution

Correct answer: A

Which of the following interferes with the Biuret Assay results?
A) Detergents
B) (NH₄)₂SO₄ and Urea
C) Alcohol
D) Phosphate buffer

Correct answer: B

The sensitivity of the Biuret assay is approximately limited to protein concentrations above _.
A) 1 mg/mL
B) 10 μg/mL
C) 0.1 mg/mL
D) 5 μg/mL

Correct answer: A

The final step in determining protein concentration using both Bradford and Biuret assays involves _.
A) Measuring absorbance and using a standard calibration curve
B) Adding more dye to intensify color
C) Cooling the solution to stabilize absorbance
D) Measuring pH to correct for acidity

Correct answer: A