Ch 3: Adaptive Quiz

What is the proper three‑letter abbreviation for isoleucine?

A) Isl

B) Ile

C) Iso

D) Ilu

B) Ile

Identical subunits in an oligomeric protein are called:

A) Residues

B) Conjugates

C) Protomers

D) Isomers.

C) Protomers

What is the first step in protein purification?

A) preparation of the crude extract

B) differential centrifugation

C) fractionation

D) dialysis

A) preparation of the crude extract

A consensus sequence:

A) is a molecule analyzed by a mass spectrometer

B) is a family of functionally similar proteins that exists in the same species

C) varies for a specific protein in a population

D) reflects the most common amino acid in each position

D) reflects the most common amino acid in each position

Which statement regarding amino acids is TRUE?

A) They are not all used in making proteins

B) All of the R groups are either polar or charged

C) Five of the ones used to make proteins are either acidic or basic

D) At physiological pH, they have no charges

A) They are not all used in making proteins

The oligopeptide shown can BEST be classified as a:

A) dipeptide

B) tripeptide

C) tetrapeptide

D) pentapeptide

D) pentapeptide

Researchers add sodium dodecyl sulfate (SDS) during the electrophoresis of proteins to:

A) separate proteins based exclusively on molecular weight

B) determine a protein's isoelectric point

C) determine an enzyme's specific activity

D) preserve a protein's native structure and biological activity

A) separate proteins based exclusively on molecular weight

All of the listed reagents can be used to modify the cysteine thiol group in a protein EXCEPT:

A) maleimide

B) iodoacetamide

C) benzylbromide

D) bromomethyl ketone

E) sodium dodecyl sulfate (SDS)

E) sodium dodecyl sulfate (SDS)

Aspartate has three pK_a values of 1.88, 9.60, and 3.65. What is the calculated isoelectric point (pI) of aspartate?

A) 2.77

B) 5.04

C) 6.63

D) 5.74

A) 2.77

What type of protein is chymotrypsin, as it only contains amino acids?

A) conjugated protein

B) lipoprotein

C) glycoproteins

D) simple protein

D) simple protein

In the cation exchange chromatography of amino acids, where the elution buffer is applied as a gradient from low pH to high pH, what is the order of elution (first to last) of a mixture of glycine, aspartate, and arginine?

A) glycine, arginine, aspartate

B) glycine, aspartate, arginine

C) arginine, glycine, aspartate

D) aspartate, glycine, arginine

D) aspartate, glycine, arginine

Which statement strongly supports the important relationship between primary amino acid sequence and the function of the resulting protein?

A) Proteins that carry out similar functions in distantly related species can differ greatly in overall size.

B) Proteins that carry out similar functions in distantly related species can differ greatly in overall amino acid sequence.

C) Most proteins contain specific sequences that are conserved and essential to protein function.

D) 20–30% of proteins are polymorphic.

C) Most proteins contain specific sequences that are conserved and essential to protein function.

Which statement is TRUE about proteins?

A) There are no α‑carboxyl groups

B) Proteins are not biologically active

C) Written amino acid sequences start from the N terminus

D) Proteins do not have isoelectric points

C) Written amino acid sequences start from the N terminus

What is the purpose of dicyclohexylcarbodiimide (DCC) in peptide synthesis?

A) It removes the completed peptide from the polystyrene bead.

B) It is a protecting group for carboxylic acid side chains.

C) It is a protecting group for amino side chain groups.

D) It is a coupling agent used to activate the carboxylic acid for reaction with amines.

E) It is a protecting group for the amino terminus of the peptide.

D) It is a coupling agent used to activate the carboxylic acid for reaction with amines.

How many small peptide fragments will result if you treat the peptide Gly–Ala–Leu–Arg–Ala–Lys–Gly–Arg–His–Pro–Ala with trypsin?

A) one

B) two

C) three

D) four

D) four

Which component is critical for the purification of a protein?

A) column chromatography

B) a means of detecting the protein

C) a centrifuge

D) the gene sequence of the protein

B) a means of detecting the protein

Which of the following peptides would have a +1 charge at pH 7?

A) Ala–Gly–Asn–Leu–Lys

B) Ala–Gly–Asp–Leu–Lys

C) Ala–Glu–Asn–Leu–Lys

D) Ala–Glu–Arg–Leu–Pro

E) Arg–Gln–Lys–Leu–Lys

A) Ala–Gly–Asn–Leu–Lys

How many small peptide fragments will result if you treat the peptide Gly–Trp–Ala–Leu–Arg–Ala–Lys–Trp–Gly–Arg–Phe–His–Pro–Ala–Tyr with pepsin?

A) one

B) four

C) five

D) six