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Theme 3

Frage 1 von 50

1

In a protein, the most conformationally restricted amino acid is ______; the least conformationally restricted is

Wähle eine der folgenden:

  • Trp, Gly

  • Met, Cys

  • Pro, Gly

  • Ile, Ala

  • Ala, Pro

Erklärung

Frage 2 von 50

1

Which one of these characteristics is not true for the  helix?

Wähle eine der folgenden:

  • There are 3.6 amino acids per turn.

  • There is a requirement for glycine every third amino acid residue.

  • A hydrogen bond forms between the carbonyl oxygen of the nth amino acid residue and the -NH group of the (n + 4)th amino acid residue.

  • Proline is typically not found in the  helix.

  • It is right-handed.

Erklärung

Frage 3 von 50

1

Which of these characteristics does not describe the  sheet?

Wähle eine der folgenden:

  • Amino acid side chains are located both above and below the sheet.

  • B-sheets have a pleated edge-on appearance.

  • They can exist in either parallel or antiparallel configurations.

  • The sheets contain as few as two and as many as 22 polypeptide chains.

  • Parallel B-sheets containing fewer than five chains are the most common

Erklärung

Frage 4 von 50

1

Which statement below does not describe fibrous proteins?

Wähle eine der folgenden:

  • Domains have a globular fold

  • These proteins usually contain only one type of secondary structure.

  • These proteins usually exhibit structural or protective characteristics.

  • These proteins have usually elongated hydrophilic surfaces.

  • These proteins are usually insoluble in water.

Erklärung

Frage 5 von 50

1

Which of the following changes would not alter the functional characteristics of α keratin?

Wähle eine der folgenden:

  • Increasing the number of residues per turn to 4.1 while maintaining the same amino acid sequence.

  • Substitution of a hydrophilic amino acid for a hydrophobic amino acid at position a and d of the 7-residue pseudorepeat.

  • Decreasing the number of cysteine amino acids within each protofilament

  • Changing the environment surrounding the protein to one that is more reductive

  • All of the above would alter the functional characteristics of keratin

Erklärung

Frage 6 von 50

1

Which of the following statements is true regarding collagen?

Wähle eine der folgenden:

  • The inability to hydroxylate proline results in the inability to synthesize collagen.

  • The α helical structure is ideal for intertwining 3 filaments.

  • Hydrogen bonds between the ─OH groups of Hyp residues stabilize the helix.

  • The requirement for glycine every 3rd amino acid is essential for the triplet helix formation.

  • On average, there is one proline for every hydroxyproline.

Erklärung

Frage 7 von 50

1

Which of the following gives the best example of a nonrepetitive structure in a protein?

Wähle eine der folgenden:

  • a random sequence of 12 amino acids with high Pα values forming an α helix

  • an amino acid sequence with the following pattern "…a-b-c-d-e-a-b-c-d-a-b-c-d…"

  • a 13 residue α helix with a Gln at position n+12 which hydrogen bonds to a residue at position n+10

  • All of the above statements describe nonrepetitive protein structures.

  • None of the above describe nonrepetitive protein structures.

Erklärung

Frage 8 von 50

1

In the absence of ascorbic acid, prolyl oxidase is unable to oxidize proline residues in collagen to hydroxyproline, resulting in:

Wähle eine der folgenden:

  • lathyrism

  • prion diseases

  • amyloid formation

  • scurvy

  • allysine

Erklärung

Frage 9 von 50

1

Of the following, which amino acid is most likely to be found in position 1 or 4 on α keratin?

Wähle eine der folgenden:

  • phe

  • ala

  • lys

  • trp

  • pro

Erklärung

Frage 10 von 50

1

Which of the following amino acids combinations have side chains with groups that have the greatest ability to stabilize the tertiary structure of a protein?

Wähle eine der folgenden:

  • Lys and Arg

  • Cys and Glu

  • Glu and Lys

  • Gln and Glu

  • Pro and Asp

Erklärung

Frage 11 von 50

1

The low pH found in the gut can enhance the digestibility of dietary protein by causing

Wähle eine der folgenden:

  • amide hydrolysis

  • protein denaturation

  • disulfide reduction

  • prion formation

  • cysteine oxidation

Erklärung

Frage 12 von 50

1

Which of the following occurs first when folding a disordered polypeptide chain into a stable protein formation?

Wähle eine der folgenden:

  • formation of a low energy state

  • association of ordered subunits

  • aggregation of hydrophobic regions in the protein

  • tertiary structure refinement

  • formation of a low entropy state

Erklärung

Frage 13 von 50

1

Imagine that a researcher treated a protein with a high concentration of a chaotropic agent. Which of the following is the most likely result of the treatment?
I. Nonpolar portions of the protein become more soluble.
II. The protein begins to denature ,
III. The protein stability increases due to hydrophobic collapse

Wähle eine der folgenden:

  • I,II,III

  • I, II

  • II, III

  • I, III

  • II

Erklärung

Frage 14 von 50

1

For B-sheets, the terms ‘parallel’ and ‘antiparalllel’ refer to ___________.

Wähle eine der folgenden:

  • the ‘direction’ of the associated peptide strands

  • the orientation of the amide cross-links

  • the quaternary structure of the protein

  • the orientation of the hydrogen bonding

  • the topology of the reverse turns

Erklärung

Frage 15 von 50

1

In general molecular chaperone proteins function by

Wähle eine der folgenden:

  • mediating disulfide bond formation

  • synthesizing new proteins when one is misfolded.

  • preventing premature folding by binding hydrophobic regions of the protein.

  • enhancing salt bridge formation.

  • none of the above

Erklärung

Frage 16 von 50

1

When comparing similarities among multiple protein structures, which of the following is false?

Wähle eine der folgenden:

  • Proteins with the same function from a different species are likely to have similar motifs.

  • Proteins with the same function from different species are likely to be more similar in sequence than in structure.

  • An effective protein motif isl likely be observed in multiple proteins.

  • Proteins with the same motifs are likely to perform similar functions.

  • None of the above statements are false

Erklärung

Frage 17 von 50

1

The structure and sequence of a protein of unknown function was examined. Which of the following provides the best prediction of the protein's function?

Wähle eine der folgenden:

  • the observation of several disordered α helical domains.

  • the observation of multiple protein subunits.

  • the observation of motif known as the Rossmann fold.

  • the observation of a large number of random coil regions.

  • All of the above offer excellent prediction of the protein's function

Erklärung

Frage 18 von 50

1

Noncovalent forces that stabilize protein structure include all of the following except

Wähle eine der folgenden:

  • the hydrophobic effect

  • salt bridges

  • electrostatic interactions with metal ions

  • hydrogen bonding

  • disulfide bridges

Erklärung

Frage 19 von 50

1

The classic experiment demonstrating that reduced and denatured RNase A could refold into the native form demonstrates that:

Wähle eine der folgenden:

  • 1° structure can determine 3° structure

  • denaturation does not disrupt protein 2° structure

  • disulfide bonds do not stabilize folded proteins

  • All of the above.

  • None of the above

Erklärung

Frage 20 von 50

1

The first step in the folding of disordered polypeptides into ordered functional protein is the formation of ______.

Wähle eine der folgenden:

  • 1 structure

  • 2 structure

  • 3 structure

  • 4 structure

  • hydrogen bonds

Erklärung

Frage 21 von 50

1

Evolutionary processes have

Wähle eine der folgenden:

  • increased the stability of 4° structures.

  • decreased the number of subunits.

  • increased similarity amount 1° structures.

  • enhanced efficient folding pathways.

  • all of the above

Erklärung

Frage 22 von 50

1

Chaperonins such as the GroEL/ES system

Wähle eine der folgenden:

  • function with thermophilic proteins only.

  • are required at low pH

  • require ATP hydrolysis

  • in vitro only.

  • function in a nonaqueous environment.

Erklärung

Frage 23 von 50

1

Protein diseases can be caused by which of the following

Wähle eine der folgenden:

  • mutations affecting the 1° structure.

  • mutations affecting the 3° structure.

  • changes in the post-synthetic processing of proteins.

  • All of the above are potential causes.

  • None of the above are potential causes

Erklärung

Frage 24 von 50

1

Which of the following would be most stable based on the information you have learned about protein structure?

Wähle eine der folgenden:

  • a loop region with 8 amino acids

  • a β sheet region made up of amino acids Val, Ile, Phe

  • an α helix made up of Cys, Pro, and Phe

  • a β hairpin with 12 amino acids

  • All have equal stability.

Erklärung

Frage 25 von 50

1

Hydrogen bonds and maximum separation of amino acid side chains make the _____very stable and energetically ______________.

Wähle eine der folgenden:

  • α helix and β sheet, favorable

  • α helix, unfavorable

  • β sheet, unfavorable

  • α helix, favorable

  • β sheet, favorable

Erklärung

Frage 26 von 50

1

A chaperonin

Wähle eine der folgenden:

  • helps fold some proteins in their lowest energy state.

  • is required for all proteins to fold properly.

  • mediates the unfolding of proteins.

  • is required for protein denaturation

  • counteracts the laws of thermodynamics.

Erklärung

Frage 27 von 50

1

A helix has hydrogen bonds between the carbonyl group from residue “n” and the amino group of residue “n+6,” which of the following is TRUE?

Wähle eine der folgenden:

  • It has 3.6 residues per turn.

  • It is a random coil, not a helix.

  • It is an α helix.

  • It has more residues per turn than an α helix.

  • It has fewer residues per turn than an α helix.

Erklärung

Frage 28 von 50

1

Which of the following contribute to the minimization of energy that occurs with protein folding?

Wähle eine der folgenden:

  • orientating amino acid groups to maximize hydrogen bonding

  • folding hydrophobic groups towards the exterior of the protein

  • burying polar groups towards the interior of the protein

  • extensive cavity formation

  • all of the above

Erklärung

Frage 29 von 50

1

Which of the following best describes the cause of Creutzfeld-Jakob Disease (a disease which human can develop with symptoms similar to those of mad cow disease)?

Wähle eine der folgenden:

  • aggregation of a misfolded protein

  • aggregation of random coil regions on a protein

  • ingestion of ammonium salts

  • the serious side effects of experimental treatment with Quinacrine

  • All are potential causes Creutzfeld-Jakob disease.

Erklärung

Frage 30 von 50

1

Proteins can denature due to a change in

Wähle eine der folgenden:

  • pH

  • temperature

  • ionic strength

  • all of the above

  • none of the above

Erklärung

Frage 31 von 50

1

48. Examine the three sequences below for collagen-like proteins. If hydrogen bonding were the most important feature in determining strength in fibrous proteins, which of the following sequences likely has the highest melting temperature and why? (Note: Flp = fluoroproline; Hyp = hydroxyproline)

I. Pro-Hyp-Gly-Pro-Hyp-Gly-Pro-Hyp-Gly
II. Pro-Flp-Gly-Pro-Flp-Gly-Pro-Flp-Gly
III. Gly-Pro-Thr-Gly-Pro-Thr-Gly-Pro-Thr

Wähle eine der folgenden:

  • “1” because Hyp has OH groups

  • “1” because the electronegativity of oxygen is greater

  • “2” because the electronegativity of proline is greater

  • “3” because Thr is a small amino acid which allows close packing

Erklärung

Frage 32 von 50

1

Based on what you know about fibrous protein structure and sequence, what type of fibrous protein is this sequence most likely to from (You can assume that the protein is longer than what is shown and is repeating as shown, also note the polarity of each amino acid.)?
Val – Cys – Lys – Val - Cys – Ala – Cys - Val – Cys – Lys – Val - Cys – Ala – Cys

Wähle eine der folgenden:

  • alpha-keratin

  • beta-keratin

  • collagen

  • pleated collagen

Erklärung

Frage 33 von 50

1

Which of the following structural proteins has the greatest elasticity?

Wähle eine der folgenden:

  • alpha-keratin

  • beta-keratin

  • collagen

  • pleated collagen

Erklärung

Frage 34 von 50

1

Noncovalent interactions account for the strength of which of the following structural proteins?

Wähle eine der folgenden:

  • alpha-keratin

  • collagen

  • pleated collagen

  • A and B

  • B and C

Erklärung

Frage 35 von 50

1

When considering fibrous proteins, which of the following statements is TRUE?

Wähle eine der folgenden:

  • noncovalent interactions contribute to the strength of all these proteins

  • all of them consist of alpha-helix structure

  • all of them require vit C

  • decrease in amounts of any of them cause scurvy

  • all of these are true of fibrous proteins

Erklärung

Frage 36 von 50

1

Which of the characteristics of collagen structure listed below contrubute to the tensi
le strength of collagen?
I. Collagen is made up of a triplet helix where 3 left-handed helices twist together in a right handed sense.
II. Collagen includes at repeating sequence of amino acids with glycine every 3 amino acids in a helix with about 3 amino acids per turn.
III. The three left-handed helices are staggered to allow close packing between glycine residues and rigidity from the bulky and inflexible proline/hydroxyproline.

Wähle eine der folgenden:

  • I

  • I, II

  • I, II, III

  • II, III

  • I, III

Erklärung

Frage 37 von 50

1

Molecular chaperones bind to unfolded or partially folded polypeptide chains in order to accomplish which of the following?

Wähle eine der folgenden:

  • ensure that improper aggregation of hydrophobic segments does not occur

  • engulf the protein in order to ensure that the protein is not damaged by heat denaturation

  • facilitate native folding by exposing hydrophobic segments of the protein as it is synthesized

  • facilitate aggregation of multiple subunits of a protein during synthesis

  • All of the above are accomplished by molecular chaperones.

Erklärung

Frage 38 von 50

1

What observation about protein refolding or renaturation helped to solidify the connection between primary amino acid sequence and 3-D structure?

Wähle eine der folgenden:

  • Spontaneous refolding of proteins into their native state under physiologic conditions.

  • Assisted refolding of proteins into their native state under laboratory conditions.

  • Identification of thermostable proteins than maintain their native state in adverse temperatures.

  • A and B

  • B and C

Erklärung

Frage 39 von 50

1

Native protein purifications often require multiple reaction steps in order to purify the protein of interest from other proteins. One method used for protein separation in purification procedures is a change from water to an organic solvent. Which of the following would be accomplished by this solvent change?

Wähle eine der folgenden:

  • Proteins with hydrophobic groups on the interior would maintain their native state.

  • Proteins with hydrophilic groups on the exterior would denature and likely precipitate

  • Proteins with exposed hydrophobic groups would maintain their structure and remain in solution

  • Both A and B would occur.

  • Both B and C would occur.

Erklärung

Frage 40 von 50

1

When solving a protein structure using X-ray crystallography, the crystallographer generates a 3-D grid called an electron density map based on the observed diffraction pattern. The higher the resolution, the more detailed the electron density map and therefore the easier it is to identify what atoms (and therefore what amino acids) are in a given position. Based on the three choices below, in which of the following groups could the two of amino acids be the easiest to differentiate regardless of resolution?
I. Leucine vs. Isoleucine
II. Phenylalanine vs. Alanine
III. Glutamate vs. Glutamic acid

Wähle eine der folgenden:

  • Those in both groups I and II could be differentiated

  • Those in both groups I and III could be differentiated

  • Only those in group II could be differentiated

  • Only those in group III could be differentiated

  • Only those in groupI could be differentiated

Erklärung

Frage 41 von 50

1

The most important contribution to the stability of a protein’s conformation appears to be the:

Wähle eine der folgenden:

  • entropy increase from the decrease in ordered water molecules forming a solvent shell around it.

  • maximum entropy increase from ionic interactions between the ionized amino acids in a protein.

  • sum of free energies of formation of many weak interactions among the hundreds of amino acids in a protein

  • sum of free energies of formation of many weak interactions between its polar amino acids and surrounding water

  • stabilizing effect of hydrogen bonding between the carbonyl group of one peptide bond and the amino group of another.

Erklärung

Frage 42 von 50

1

In an aqueous solution, protein conformation is determined by two major factors. One is the formation of the maximum number of hydrogen bonds. The other is the:

Wähle eine der folgenden:

  • formation of the maximum number of hydrophilic interactions.

  • maximization of ionic interactions.

  • minimization of entropy by the formation of a water solvent shell around the protein.

  • placement of hydrophobic amino acid residues within the interior of the protein.

  • placement of polar amino acid residues around the exterior of the protein.

Erklärung

Frage 43 von 50

1

In an alpha-helix, the R groups on the amino acid residues:

Wähle eine der folgenden:

  • alternate between the outside and the inside of the helix.

  • are found on the outside of the helix spiral.

  • cause only right-handed helices to form.

  • generate the hydrogen bonds that form the helix.

  • stack within the interior of the helix.

Erklärung

Frage 44 von 50

1

The major reason that antiparallel beta-stranded protein structures are more stable than parallel beta-stranded structures is that the latter:

Wähle eine der folgenden:

  • are in a slightly less extended configuration than antiparallel strands.

  • do not have as many disulfide crosslinks between adjacent strands.

  • do not stack in sheets as well as antiparallel strands.

  • have fewer lateral hydrogen bonds than antiparallel strands.

  • have weaker hydrogen bonds laterally between adjacent strands.

Erklärung

Frage 45 von 50

1

The three-dimensional conformation of a protein may be strongly influenced by amino acid residues that are very far apart in sequence. This relationship is in contrast to secondary structure, where the amino acid residues are:

Wähle eine der folgenden:

  • always side by side

  • generally near each other in sequence

  • invariably restricted to about 7 of the 20 standard amino acids

  • often on different polypeptide strands

  • usually near the polypeptide chain’s amino terminus or carboxyl terminus

Erklärung

Frage 46 von 50

1

Proteins often have regions that show specific, coherent patterns of folding or function. These regions are called:

Wähle eine der folgenden:

  • domains

  • oligomers

  • peptides

  • sites

  • subunits

Erklärung

Frage 47 von 50

1

An average protein will not be denatured by

Wähle eine der folgenden:

  • a detergent such as sodium dodecyl sulfate.

  • heating to 90°C

  • iodoacetic acid

  • pH 10.

  • urea.

Erklärung

Frage 48 von 50

1

Which of the following is least likely to result in protein denaturation?

Wähle eine der folgenden:

  • altering net charge by changing pH

  • changing the salt concentration

  • disruption of weak interactions by boiling

  • exposure to detergents

  • mixing with organic solvents such as acetone

Erklärung

Frage 49 von 50

1

Protein S will fold into its native conformation only when protein Q is also present in the solution. However, protein Q can fold into its native conformation without protein S. Protein Q, therefore, may function as a ____________ for protein S.

Wähle eine der folgenden:

  • ligand

  • molecular chaperone

  • protein precursor

  • structural motif

  • supersecondary structural unit

Erklärung

Frage 50 von 50

1

Which of the following is not known to be involved in the process of assisted folding of proteins?

Wähle eine der folgenden:

  • chaperonins

  • disulfide interchange

  • heat shock proteins

  • peptide bond hydrolysis

  • peptide bond isomerization

Erklärung

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