Deck 5: Proteins: Their Primary Structure and Biological Functions

Question 1

Which of the following techniques involves using a strongly acidic,polystyrene resin,chromatography column?

A)gas-liquid chromatography
B)ion exchange chromatography
C)partition chromatography
D)liquid-liquid partition chromatography

Answer 1

B

Question 2

Which of the following is a property common to fibrous proteins?

A)They are highly soluble in water.
B)Their hydrophilic residues are directed into the interior of the protein.
C)They exhibit enzymatic activity.
D)They serve structural roles in cells.

Answer 2

D

Question 3

Which structural classification best describes glutamine synthetase found in E.coli?

A)monomer
B)heterotrimer
C)homomultimer
D)heteromultimer

Answer 3

C

Question 4

Which of the following amino acid residues is destroyed by acid hydrolysis and must be estimated by other means?

A)tyrosine
B)tryptophan
C)valine
D)isoleucine

Question 5

Which level of structural organization best describes the amino acid sequence of a protein?

A)primary
B)secondary
C)tertiary
D)quaternary

Question 6

What is the following terms refers to a protein with 2 different polypeptide chains?

A)monomeric protein
B)homodimeric protein
C)heterodimeric protein
D)trimeric protein

Question 7

Which of the following is a property common to globular proteins?

A)They are soluble in water.
B)They are roughly linear in structure.
C)They fold so that the hydrophilic amino acids are in the interior of the molecule.
D)The hydrophobic side chains are exposed to the surrounding water.

Question 8

Which of the following factors determines a protein's particular conformation?

A)the overall 2-dimensional architecture of the protein
B)the breaking and reforming of covalent bonds
C)the rotations about every second bond along the peptide backbone
D)the amino acid side-chain interactions

Question 9

The formation of a disulfide bond is an example of what level(s)of protein structure?

A)primary and secondary
B)secondary and tertiary
C)tertiary and quaternary
D)quaternary

Question 10

Which of the following is a feature of membrane proteins?

A)They have membrane-associated amino acids with polar side chains.
B)They are much more soluble in detergents than in water.
C)They have hydrophobic amino acids that are oriented inward.
D)They have a globular structure.

Question 11

What type of bond is formed when 2 cysteine residues react in proteins?

A)thioester bond
B)thioether bond
C)dithiol bond
D)disulfide bond

Question 12

Which of the following is a characteristic of all molecules of a given protein?

A)a variable amino acid composition
B)a random amino acid sequence
C)a nucleotide sequence from which they are encoded
D)an amino acid sequence read from C-terminal end to N-terminal end

Question 13

Which level of structural organization contains all the information necessary for a protein to achieve its intricate architecture?

A)primary
B)secondary
C)tertiary
D)quaternary

Question 14

Which of the following best defines a gene?

A)a segment of DNA nucleotide bases that encode for the synthesis of a particular protein
B)a single strand of DNA that is designated as the sense strand
C)a functional segment of a unique protein
D)the segment of DNA that is changed in a mutation

Question 15

Which of the following factors is NOT considered a level of protein structure?

A)the interaction between subunits of a protein
B)the order of amino acid residues in the peptide chain
C)the 3-dimensional arrangement of all atoms in a single peptide
D)the hydrogen bond arrangement of nonpolar R-groups

Question 16

Which of the following techniques is used for protein isolation and purification?

A)ion exchange chromatography
B)Edman degradation
C)PCR
D)gas-liquid chromatography

Question 17

Which of these atoms would be found in the amide plane of the peptide backbone?

A)H bound to the amide nitrogen
B)side chain carbons
C)Ca-carbon
D)O bound to the carbonyl carbon

Question 18

Which level of structural organization best describes the a-helix and b-strand components of protein structure?

A)primary
B)secondary
C)tertiary
D)quaternary

Question 19

What is the repeated sequence in the peptide backbone of a protein given that Cₐ,N and Cₒ represent the a-carbon,the amide nitrogen,and the carbonyl carbon,respectively?

A)-Ca- Co-N
B)-N-Co-Ca-
C)-N-Ca-Co-
D)-Co-Ca-N-

Question 20

Using a cation-exchange resin,a mixture of 4 amino acids is separated using an elution gradient of increasing NaCl solution.What would be the correct elution sequence?

A)Arg,Asp,Lys,Ser
B)Lys,Arg,Asp,Ser
C)Asp,Ser,Lys,Arg
D)Ser,Asp,Lys,Arg

Question 21

Suppose a protein is treated with trypsin.Which of the following techniques could be used to determine its identity by peptide mass fingerprinting?

A)NMR
B)MALDI-TOF mass spectrometry
C)HPLC
D)gel electrophoresis

Question 22

Which of the following terms is used to characterize proteins destined for an extracellular location?

A)phosphoproteins
B)glycoproteins
C)lipoproteins
D)flavoproteins

Question 23

Which of the following best describes the use of the Edman degradation procedure?

A)determining the C-terminal amino acid using a carboxypeptidase
B)cleaving a protein into a multitude of smaller peptides
C)comparing overlapping sets of peptide fragments
D)determining the N-terminal amino acid

Question 24

What is the overall net charge on the peptide Lys-Lys-Ser-Glu at pH 7.0?

A)+2
B)+1
C)-1
D)-2

Question 25

Suppose that the peptide Ala-Met-Lys-Ser is reacted with phenylisothiocyanate at pH 8.0,followed by mild acidification,which is the first cycle of Edman method? Which of the following would be released?

A)the labelled peptide Ala-Met-Lys-Ser-PTH
B)PTH-Ala,PTH-Ser,PTH-Lys,and PTH-Met
C)PTH-Ser and the peptide Ala-Met-Lys
D)PTH-Ala and the peptide Met-Lys-Ser

Question 26

Insulin is a polypeptide hormone that contains 2 short polypeptide chains linked by 2 interstrand disulfide bonds.Which of the following treatments would NOT be useful for determining its primary structure?

A)reduction of the peptides with SDS
B)sequencing of the peptides with Edman chemistry
C)separation of the peptides by chromatography techniques
D)alkylation of the peptides with iodoacetate

Question 27

Which of the following molecules specifically hydrolyzes only those peptide bonds in which the carboxyl function is contributed by an arginine or a lysine residue?

A)chymotrypsin
B)carboxypeptidase
C)trypsin
D)CNBr

Question 28

Which of the following does NOT apply to the amino acid sequence of proteins?

A)It is encoded by the nucleotide sequence of DNA.
B)It is a form of genetic information.
C)It is read from N-terminal end to C-terminal end.
D)It is constant for proteins with the same function from different organisms.

Question 29

Various mutations can occur in the hemoglobin molecule resulting in the generation of very diverse mutants.What does the generation of this diversity indicate?

A)that any amino acid that is changed in the sequence is relatively important
B)that any amino acid that is changed in the sequence is lethal to the organism
C)that a specific amino acid changed in the sequence can drastically the function of the protein
D)that any amino acid change will have the same effect on the protein function

Question 30

Which of the following treatments is NOT a useful method for dissociating a heteromultimeric protein during sequencing?

A)high salt concentrations
B)6 N HCl at 110°C for 24 hours
C)8 M urea
D)6 M guanidinium chloride

Question 31

Which of the following characteristics about the peptide Val-Asp-Trp-Asn-Ser is correct?

A)It would show a strong absorption band at 280 nm.
B)Reaction with clostripain would yield 2 peptides.
C)After the second round of Edman degradation using the reagent PITC,the PTH-amino acid residue released would be PTH-Asn.
D)It is resistant to trypsin.

Question 32

Which of the following is a characteristic of homologous proteins from different organisms?

A)They have very little sequence similarity with other proteins with similar function.
B)They have nearly identical lengths.
C)They do not share a significant degree of sequence similarity.
D)They have sequence similarity indirectly correlated to the relatedness of the species from which they were derived.

Question 33

When sequencing a protein,which of the following is an advantage of treating separate samples of the protein with 2 or more enzymes?

A)The products are homogeneous.
B)The products are sequenceable without further chromatography.
C)The products are fragments with the same N- and C-terminal amino acids.
D)The products are fragments with sequence overlaps.

Question 34

Which of the following tproteins do not perform any obvious chemical transformation,but control the ability of other proteins to carry out their physiological functions?

A)regulatory
B)transport
C)storage
D)structural

Question 35

Which of the following proteases can be used to identify the C-terminal residue of a polypeptide?

A)chymotrypsin
B)carboxypeptidase
C)trypsin
D)elastase

Question 36

Which of the following proteins has a significant degree of sequence similarity and tertiary structure with hen egg white lysozyme?

A)trypsin
B)a-lactalbumin
C)thrombin
D)hemoglobin

Question 37

Which of the following products are formed from the acid hydrolysis of a simple amide?

A)aldehyde and alcohol
B)acid and amine
C)ester and alcohol
D)amine and aldehyde

Question 38

Which of the following is determined by amino acid analysis of a protein?

A)the amino acid sequence of the protein
B)the number of residues of each amino acid in the protein
C)the identification of the N-terminal and C-terminal amino acids
D)the percentage of the various amino acids in the protein

Question 39

Which of the following characteristics about the peptide Lys-Met-Cys-Phe-Ala-Trp is correct?

A)It has a molecular weight around 700 kDa and shows a strong absorption band at 280 nm.
B)Treatment with carboxypeptidase results in lysine and a peptide.
C)Trypsin digestion produces an amino acid and a pentapeptide with Met on the amino end.
D)Chymotrypsin digestion yields 2 tripeptides.

Question 40

Which of the following is now the most commonly used technique for finding the sequence of proteins?

A)chemical sequencing
B)mass spectrometry
C)HPLC
D)gene transcription and translation

Question 41

Which of the following protein terms describes the lac repressor?

A)regulatory
B)transport
C)storage
D)structural

Question 42

Which of the following protein terms describes hemoglobin?

A)regulatory
B)transport
C)storage
D)structural

Question 43

Which of the following protein terms describes collagen?

A)regulatory
B)transport
C)storage
D)structural