Biochem Chapter 6 (Dont think any are from here)

Which of the following structural proteins has the greatest elasticity? A) a keratin B) β ketatin C) collagen D) pleated collagen E) A and B are equal

D - pleated collagen has greatest elacticity

In the absence of ascorbic acid, prolyl oxidase is unable to oxidize proline residues in collagen to hydroxyproline, resulting in: A) lathyrism B) prion diseases C) amyloid formation D) scurvy E) allysine

D - scurvy results from no ascorbic acid

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 A) "1" because Hyp has OH groups B) "1" because the electronegativity of oxygen is greater C) "2" because the electronegativity of proline is greater D) "2" because the electronegativity of the -OH group increases hydrogen bond strength E) "3" because Thr is a small amino acid which allows close packing

A

When considering fibrous proteins, which of the following statements is TRUE? A) Noncovalent interactions contribute to the strength of all of these proteins. B) All of them consist of alpha helix structure. C) All of them require vitamin C. D) Decrease in amounts of any of them cause scurvy. E) All of these are true of fibrous proteins.

A - all fibrous proteins strengths are due to NONcovalent interactions (like collagen)

Molecular chaperones bind to unfolded or partially folded polypeptide chains in order to accomplish which of the following? A) ensure that improper aggregation of hydrophobic segments does not occur B) engulf the protein in order to ensure that the protein is not damaged by heat denaturation C) facilitate native folding by exposing hydrophobic segments of the protein as it is synthesized D) facilitate aggregation of multiple subunits of a protein during synthesis E) All of the above are accomplished by molecular chaperones.

A - chaperones make sure aggregation of hydrophobic segments does not occur

For beta-sheets, the terms 'parallel' and 'antiparalllel' refer to ___________. A) the 'direction' of the associated peptide strands B) the orientation of the amide cross-links C) the quaternary structure of the protein D) the orientation of the hydrogen bonding D) the topology of the reverse turns

A - direction

Which statement below does not describe fibrous proteins? A) Domains have a globular fold. B) These proteins usually contain only one type of secondary structure. C) These proteins usually exhibit structural or protective characteristics. D) These proteins have usually elongated hydrophilic surfaces. E) These proteins are usually insoluble in water.

A - globular and fibrous certainly dont go together

In a Ramachandran diagram the region representing the angles of and that correspond to those commonly made by an amino acid that favors a left-handed helix are different from those angles commonly made by an amino acid that favors right-handed helix formation. Which of the following statements provides a plausible explanation for this difference? A) Groups which would normally undergo high steric hindrance in the right-handed arrangement are separated maximally in the left-handed arrangement. B) Left-handed helices have smaller pitch than right-handed helices. C) The peptide backbone can coil tighter in the left-handed helices than in the right-handed helices. D) Left-handed helices exhibit cyclic symmetry, while righthanded helices are asymmetric. E) All of the above are plausible explanations.

A - high steric hindrance in the right

Hydrogen bonds and maximum separation of amino acid side chains make the _____very stable and energetically ______________. A) α helix and β sheet, favorable B) α helix, unfavorable C) β sheet, unfavorable D) α helix, favorable E) β sheet, favorable

A- a helix and b sheets are stabalized by H bonds and energetically favorable

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 A) alpha keratin B) β keratin C) collagen D) pleated collagen E) This sequence cannot be from any of the structural proteins.

A- a keratin

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)? A) aggregation of a misfolded protein. B) aggregation of random coil regions on a protein. C) ingestion of ammonium salts. D) the serious side effects of experimental treatment with Quinacrine E) All are potential causes Creutzfeld-Jakob disease.

A- aggregating a misfolded protein can cause Jakob

A chaperonin A) helps fold some proteins in their lowest energy state. B) is required for all proteins to fold properly. C) mediates the unfolding of proteins. D) is required for protein denaturation. E) counteracts the laws of thermodynamics.

A- helps foldingggg

Which of the following contribute to the minimization of energy that occurs with protein folding? A) orientating amino acid groups to maximize hydrogen bonding B) folding hydrophobic groups towards the exterior of the protein C) burying polar groups towards the interior of the protein D) extensive cavity formation E) all of the above

A- orientation of a.a groups is important to keep low energy while folding

Of the following, which amino acid is most likely to be found in position 1 or 4 on α keratin? A) Phe B) Ala C) Lys D) Trp E) Pro

B - Ala is likely to be found in keratin 1 or 4 position

The low pH found in the gut can enhance the digestibility of dietary protein by causing ___. A) amide hydrolysis B) protein denaturation C) disulfide reduction D) prion formation E) cysteine oxidation

B - acid denaturaizes protein

Which of the following would be most stable based on the information you have learned about protein structure? A) a loop region with 8 amino acids B) a β sheet region made up of amino acids Val, Ile, Phe C) an α helix made up of Cys, Pro, and Phe D) a β hairpin with 12 amino acids E) All have equal stability.

B - beta sheet with Val, Ile and Phe will be most stable

The first step in the folding of disordered polypeptides into ordered functional protein is the formation of ______. A) 1o structure B) 2° structure C) 3° structure D) 4° structure E) hydrogen bonds

B - secondary structure first

Noncovalent interactions account for the strength of which of the following structural proteins? A) a keratin B) collagen C) pleated collagen D) A and B E) B and C

B - triple helix is strength not covalebt interaction

Examine the three sequences below for collagen-like proteins and their melting temperatures (Tm). (Note: Flp = fluoroproline; Hyp = hydroxyproline) Based on this data, what is the most important feature in determining the strength of the collagen protein? 1) ...-Pro-Hyp-Gly-Pro-Hyp-Gly-Pro-Hyp-Gly-... Tm=60oC 2) ...-Pro-Flp-Gly-Pro-Flp-Gly-Pro-Flp-Gly-... Tm=78oC 3) ...-Gly-Pro-Thr-Gly-Pro-Thr-Gly-Pro-Thr-... Tm=30oC A) hydrogen bonding B) inductive effect C) electrostatic effect D) electrostatic and Inductive effect are equal E) hydrogen bonding and inductive effect are equal

B- inductive effect

When comparing similarities among multiple protein structures, which of the following is false? A) Proteins with the same function from a different species are likely to have similar motifs. B) Proteins with the same function from different species are likely to be more similar in sequence than in structure. C) An effective protein motif isl likely be observed in multiple proteins. D) Proteins with the same motifs are likely to perform similar functions. E) None of the above statements are false.

B- proteins with same function from diff species are not likely to be more similar in sequence

Which of the following occurs first when folding a disordered polypeptide chain into a stable protein formation? A) formation of a low energy state B) association of ordered subunits C) aggregation of hydrophobic regions in the protein D) tertiary structure refinement E) formation of a low entropy state

C

Chaperonins such as the GroEL/ES system A) function with thermophilic proteins only. B) are required at low pH. C) require ATP hydrolysis. D) in vitro only. E) function in a nonaqueous environment.

C - Chaperons require ATP hydrolysis

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? A) Lys and Arg B) Cys and Glu C) Glu and Lys D) Gln and Glu E) Pro and Asp

C - Glu and Lys - are opposite charges thus can protonate or deprotante

Conventional one dimensional NMR spectroscopy is not generally an effective tool for determination of protein structure because... I. Proteins (including small proteins) have a high number of hydrogen atoms. II. NMR requires a high quality protein crystal. III. The NMR spectra exhibit high peak overlap. A) I and II B) II and III C) I and III D) I, II, and III E) III only

C - NMR shows high H atom count and peak overlap

In a protein, the most conformationally restricted amino acid is ______; the least conformationally restricted is ______. A) Trp, Gly B) Met, Cys C) Pro, Gly D) Ile, Ala E) Ala, Pro

C - Pro and Gly

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? A) the observation of several disordered α helical domains. B) the observation of multiple protein subunits. C) the observation of motif known as the Rossmann fold. D) the observation of a large number of random coil regions. E) All of the above offer excellent prediction of the protein's function.

C - Rossmann fold is a good prediction of a proteins function

Which of the following gives the best example of a nonrepetitive structure in a protein? A) a random sequence of 12 amino acids with high Pα values forming an α helix B) an amino acid sequence with the following pattern "...a-b-c-d-e-a-b-c-d-a-b-c-d..." C) a 13 residue α helix with a Gln at position n+12 which hydrogen bonds to a residue at position n+10 D) All of the above statements describe nonrepetitive protein structures. E) None of the above describe nonrepetitive protein structures.

C - a 13 residue helix with Gln at n+12

In a Ramachandran diagram, a larger area represents sterically allowed torsion angles of phi and psi that are allowed in _____ rather than in ______ because there is greater opportunity for separation of amino acid side chains. A) secondary structure...tertiary structure B) α helix...β sheet C) β sheet...α helix D) tertiary structure...secondary structure E) none of the above

C- ALLOWED in B sheets bc greater seperation

Which of the following is true regarding crystalline proteins? A) Many crystallized enzyme proteins remain catalytically active. B) The diffractive pattern observed during X-ray exposure to the crystal can be used to calculate the electron density map of the crystalline protein. C) The larger region indicating electron density with in the electron density map, the more accurate the structure determination. D) A and B are true. E) A, B, and C are true.

D - A and B are true- Crystalline proteins remain catalyticall actuve and the defractive pattern on x-ray can calculate electron density map of crystal

Which of the following has (have) both a favorable hydrogen bonding pattern and phi and psi values that fall within the allowed Ramachandran conformational regions? A) alpha helix B) collagen helix C) beta sheet D) all of the above E) none of the above

D - Alpha, collagen and beta all are favorable

Evolutionary processes have A) increased the stability of 4° structures. B) decreased the number of subunits. C) increased similarity amount 1° structures. D) enhanced efficient folding pathways. E) all of the above

D - Folding pathways have enhanced thru evolution

Which of the following statements is true regarding collagen? A) The inability to hydroxylate proline results in the inability to synthesize collagen. B) The α helical structure is ideal for intertwining 3 filaments. C) Hydrogen bonds between the ─OH groups of Hyp residues stabilize the helix. D) The requirement for glycine every 3rd amino acid is essential for the triplet helix formation. E) On average, there is one proline for every hydroxyproline.

D - glycine 3rd residue is important for trip helix

Proteins can denature due to a change in A) pH. B) temperature. C) ionic strength. D) all of the above E) none of the above

D- allll

What structure motif most likely forms as a result of this protein sequence? A) β strand connected to another β strand with a break (or loop/turn) in between B) α Helix connect to another α Helix with a break (or loop/turn) in between C) β strand connected to another β strand with a alpha helix in between D) α Helix connected to a β strand with a break (or loop/turn) in between E) None of the above are correct.

D- alpha helix connected to B strand with a break - loop- turn- inbetween

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? A) It has 3.6 residues per turn. B) It is a random coil, not a helix. C) It is an α helix. D) It has more residues per turn than an α helix. E) It has fewer residues per turn than an α helix.

D- with n+6 will have MORE residues PER TURN then a helix

* Which of these characteristics does not describe the B sheet? A) Amino acid side chains are located both above and below the sheet. B) B sheets have a pleated edge-on appearance. C) They can exist in either parallel or antiparallel configurations. D) The sheets contain as few as two and as many as 22 polypeptide chains. E) Parallel B sheets containing fewer than five chains are the most common.

E - B sheets with 5 of fewer chains is very rare

The Protein Data Bank (PDB) is a database provides structural information about proteins that may be useful for which of the following? I. A researcher studying the changes in protein fold associated with prions. II. A researcher classifying structural elements by function. III A researcher designing a compound to bind tightly to a particular region in the protein. A) I only B) II only C) III only D) I, II E) I, II, II

E - PDB shows changes in protein folds, structural elements and specific protein regions

Which of the following changes would not alter the functional characteristics of α keratin? A) Increasing the number of residues per turn to 4.1 while maintaining the same amino acid sequence. B) Substitution of a hydrophilic amino acid for a hydrophobic amino acid at position a and d of the 7-residue pseudorepeat. C) Decreasing the number of cysteine amino acids within each protofilament. D) Changing the environment surrounding the protein to one that is more reductive. E) All of the above would alter the functional characteristics of keratin.

E - alteration of keratin due to increasing residues per turn, hydrophobic a.a substitution, decreasing cysteine a.a and changing the enviroment

Noncovalent forces that stabilize protein structure include all of the following except __________. A) the hydrophobic effect B) salt bridges C) electrostatic interactions with metal ions D) hydrogen bonding E) disulfide bridges

E - disulf are covalent