Q&A Hero

Q: The enzymes -amylase and -amylase can cleave the ____ bonds of amylopectin but not the ____ bonds.a. (1->6)-; (1->4)-b. (1->6)-; (1->4)-c. (1->4)-; (1->4)-d. (1->4)-; (1->6)-e. (1->6)-; (1->4)-

Q: Cooked starch is more digestible because: a. it has been partially hydrolyzed during cooking. b. the amylopectin is converted to amylose during cooking. c. the enzymes that hydrolyze the starch are only active when the starch is hot. d. the starch granules take up water, swell and are more accessible to the enzymes. e. all are true.

Q: In plant cells, starch is hydrolyzed by ____ to release ____ and a starch molecule with ____.a. starch phosphorylase; glucose-1-phosphate; one less glucose unitb. salivary -amylase; maltose 1-phosphate; two less glucose unitsc. starch phosphorylase; maltose 1-phosphate; two less glucose unitsd. (1->6) glucosidase; glucose-6-phosphate; one less glucose unite. starch hydrolase; glucose; one less glucose unit

Q: Because osmotic pressure depends only on ____, the osmotic pressure is greatly reduced by formation of polysaccharide molecules from monosaccharide molecules. a. molecular weight b. number of hydroxyl groups c. numbers of molecules d. numbers of hydrogen bonds e. none are true

Q: Mucopolysaccharides such as ____ form protective coats on animal cells. a. chitin b. cellulose c. glycogen d. hyaluronic acids e. glucuronic acids

Q: Cellulose is homopolysaccharide composed of ______ linked together by ______ glycosidic bonds.a. galactose; -(1->4)b. galactose; -(1->4)c. glucose; -(1->4)d. glucose; -(1->4)e. none of the above

Q: ____ is typical of the oligosaccharide components found in beans, etc., that are not digested in the stomach, but are digested by bacteria in the intestines causing flatulence. a. Melezitose b. Amygdelin c. Laetrile d. Stachyose e. Dextrantriose

Q: The cyclization of gluconic acid produces what type of structure? a. lactam b. lactone c. pyranose d. cyclic ether e. none of the above

Q: Glucuronic acid is formed by oxidation of which carbon of glucose? a. C-1 b. C-2 c. C-4 d. C-6 e. both a and b

Q: All of the following are homodisaccharides EXCEPT: a. lactose. b. maltose. c. isomaltose. d. cellobiose. e. all are homodisaccharides.

Q: Which of the following explains why the disaccharide sucrose is not a reducing sugar?a. the primary hydroxyl groups are oxidized to carboxylic acidsb. both anomeric carbons are involved in formation of the glycosidic bondc. the glycosidic bond is in the configurationd. it is composed of a furanose and a pyranosee. none of the above

Q: All of the following disaccharides are reducing sugars EXCEPT: a. lactose. b. maltose. c. sucrose. d. cellulose. e. isomaltose.

Q: Which of the following disaccharides contains an (1->4) O-glycosidic bond?a. sucroseb. lactosec. maltosed. cellobiosee. cellulose

Q: A glycosidic bond would be present in:a. -D-galactosamine.b. methyl--D-glucoside.c. 2-deoxy--D-ribose.d. -D-glucose-6-phosphate.e. -D-fructose-1, 6-bisphosphate.

Q: ____ and ____ are glycosamines linked to three-carbon acids at the C-1 or C-3 positions, and components of the polysaccharides of cell higher organisms and bacterial cell walls. a. Glucosides; galactosides b. Muramic acid; neuraminic acid c. Gluconic acid; glucuronic acid d. Sorbitol; ribitol e. None of the above

Q: All of the following are parts of the honeybee's processing of honey EXCEPT:a. producing a small amount of gluconic acid.b. concentrating the sugars to a supersaturated state.c. conversion of some glucose and fructose into sucrose.d. conversion of most of the fructose to the -D-fructopyranose form.e. producing an emulsion of glucose hydrate and fructose hydrate crystals in a thick syrup.

Q: Honey is characteristically composed predominantly of a. sucrose b. glucose and ribose c. fructose and glucose d. sucrose and sorbitol e. all of the above

Q: A constituent of the flavin coenzymes is a. sorbitol b. mannitol c. xylitol d. ribitol e. glycerol

Q: Sugar alcohols include all of the following EXCEPT: a. ribitol. b. sorbitol. c. fucose. d. mannitol. e. glycerol.

Q: Individuals with uncontrolled diabetes mellitus may have ____ levels of blood ____ so they test their blood for ____. a. elevated; fructose; gluconic acid b. depressed; glucose; oxidizing sugars c. elevated; glucose; fructose d. depressed; gluconic acid; reducing sugars e. elevated; glucose; reducing sugars

Q: All of the statements about the following pairs of sugars are correct EXCEPT: a. Galactose and mannose are diastereomers. b. L-galactose and D-galactose are enatiomers. c. Glyceraldehyde and dihydroxyacetone are stereoisomers. d. Glucose and mannose are epimers. e. Glucose has fewer chiral centers than fructose.

Q: -D-glucopyranose in the chair form is the most widely occurring form of glucose in nature and it has the following characteristics EXCEPT:a. forms a six-membered ring.b. carbon 6 is above the plane of the chair.c. all of the -­OH groups are equatorial.d. the anomeric carbon has a hydroxyl that is below the plane of the chair.e. all axial positions are occupied by -­H.

Q: As a result of mutarotation, D-glucose exists in all of the following forms EXCEPT:a. L-glucopyranose.b. -anomer.c. free aldehyde.d. -anomer.e. all are true.

Q: Which of the following is correctly paired with its most prevalent cyclization product? a. fructose: pyranose b. glucose: furanose c. ribose: pyranose d. galactose: does not cyclize e. none of the above

Q: Glucose most commonly forms which of the following structures? a. a pyranose using the hydroxyl group on carbon 4 b. a pyranose using the hydroxyl group on carbon 5 c. a pyranose using the hydroxyl group on carbon 6 d. a furanose using the hydroxyl group on carbon 3 e. a furanose using the hydroxyl group on carbon 4

Q: A cyclic hemiacetal with a six-membered oxygen-containing ring is referred to as a(n): a. aldehyde. b. pyranose. c. ketopentose. d. furanose. e. sorbitol.

Q: The formation of cyclic structures in sugars with creation of an additional asymmetric center results from an alcohol reacting with a(n): a. secondary alcohol. b. phosphate group. c. thiol group. d. aldehyde or ketone. e. primary alcohol.

Q: Mannose is an epimer of: a. ribose b. galactose c. glucose d. xylose. e. fructose.

Q: The enantiomer of D-mannose would be: a. D-galactose. b. L-glucose. c. D-glucose. d. L-mannose. e. L-arabinose.

Q: If carbon 1 is the carbonyl group of an aldohexose, which carbon determines if the sugar is a D- or L- stereoisomer? a. 1 b. 2 c. 3 d. 4 e. 5

Q: Which of the following sugars is an aldopentose? a. galactose b. ribulose c. ribose d. xylulose e. mannose

Q: Carbohydrate characteristic chemical features include all EXCEPT: a. the potential to form multiple hydrogen bonds. b. the existence of one or more asymmetric centers. c. the capacity to form polymeric structures. d. the ability to exist in either linear or ring structures. e. all are true.

Q: In the tertiary structure of a protein, a hydrophobic interaction could form between the R-groups of which two amino acids? a. Ala and Ser b. Asn and Tyr c. Leu and Val d. Val and His e. Pro and Gln

Q: In the tertiary structure of a protein, an electrostatic interaction could form between the R-groups of which two amino acids? a. Gln and Lys b. Asp and Thr c. Leu and Asp d. Glu and Arg e. Arg and His

Q: Which of the following items was one of the crucial elements of the Anfinsen experiment with ribonuclease A?a. hydrophobic interactions were disrupted by the addition of -mercaptoethanolb. correct formation of disulfide bonds was achieved even with urea presentc. removal of -mercaptoethanol resulted in complete denaturation of the proteind. the presence of 8 cysteine residues means that there are 105 different disulfide bond possibilitiese. none of the above

Q: Which of the following proteins does not have quaternary structure? a. immunoglobulins b. insulin c. glycogen phosphorylase d. myoglobin e. alcohol dehydrogenase

Q: Which of the following does not contribute to the spontaneous nature of the protein folding process? a. formation of hydrogen bonds and electrostatic interactions b. loss of translational freedom as portions of the protein interact c. formation of hydrophobic interactions d. both a and c

Q: Arrange the steps involved in folding of globular proteins into a proper sequence. A. "Molten globule" formation of assembled domains. B. Formation of domains through cooperative aggregation of folding nuclei. C. Adjustment in the conformation of domains. D. Rapid and reversible formation of local secondary structure. E. Final protein monomer formation. a. A, B, C, D, E b. B, C, E, A, D c. D, C, B, A, E d. D, B, A, C, E e. B, D, C, A, E

Q: All of the statements about the tertiary structure of the enzyme triose phosphate isomerase are correct EXCEPT:a. Its -strands are parallel.b. Its -helices are in the interior core of the molecular structure.c. It contains a -barrel in the center of its structure.d. It is composed entirely of alternating -helices and -strands.e. Hydrophobic residues are buried between concentric layers.

Q: All are structural and functional advantages to quaternary structure EXCEPT: a. cooperativity. b. stability. c. bringing catalytic sites together. d. genetic economy and efficiency. e. all are true.

Q: ____ are proteins that help other proteins to fold. a. Immunoglobulins b. Phospholipases c. Synthetases d. Molecular chaperones e. Proteases

Q: ____ is an example of a disulfide-rich protein. a. Insulin b. Glyceraldehyde-3-phosphate dehydrogenase c. Hemoglobin d. Triose phosphate isomerase e. All are true.

Q: ____ are examples of antiparallel -helix proteins.a. Triose phosphate isomeraseb. Pyruvate kinasec. Flavodoxind. Hemoglobine. Papain

Q: All are classes of globular proteins according to type and arrangement of secondary structure EXCEPT:a. small metal- and disulfide-rich proteins.b. parallel or mixed -sheet.c. antiparallel -sheet.d. antiparallel -helix.e. all are true.

Q: All are true about the tertiary structure of the enzyme triose phosphate isomerase EXCEPT:a. Its -strands are parallel.b. Its -helices are in the interior of the molecular structure.c. It contains a -barrel in the center of its structure.d. It is composed entirely of alternating -helices and -strands.e. All are true.

Q: Which statement is correct about the -­-­motif?a. The two -strands are antiparellel.b. The peptide segment connecting the -strands usually contains no more than five amino acids.c. The peptide segment connecting the two -strands commonly contains proline.d. The cross-over connection itself contains an -helical segment.e. none are correct.

Q: Which of the following would be the most rapidly occurring event giving rise to protein motion? a. hinge-bending movement between protein domains b. tyrosine ring flip c. cis-trans isomerization of proline d. protein conformational change e. both b and c are equally rapid

Q: Flexible, disordered segments of proteins are commonly high in the amino acid: a. leu b. lys c. ser d. pro e. asp

Q: A -barrel would most likely be composed of ____.a. parallel -sheets connected by regions of -helixb. parallel -sheets connected by -turns.c. parallel -sheets connected by regions of random coil.d. parallel -sheets connected disulfide bonds.e. both a and c are correct.

Q: The outward face of a(n) ____ consists mainly of polar and charged residues, whereas the inner face contains mostly nonpolar, hydrophobic residues.a. -sheetb. configurationc. -turnd. amphiphilic helixe. all are true

Q: Why should the core of most globular and membrane proteins consist almost entirely of -helix and -sheets?a. Hydrogen bonded structures must be kept away from water solvent.b. Highly polar N-­H and C=O moieties of the peptide backbone must be neutralized in the hydrophobic core of the protein.c. Hydrogen bonding only occurs in the core of proteins.d. Trapped water stabilizes the helix and sheet structures.e. None are true.

Q: In hemoglobin, a ____ protein, the space between the helices is filled efficiently and tightly with mostly ____ amino acid chains and with ____ side chains facing the outside of the protein structure. a. globular, hydrophobic, polar b. globular, polar, nonpolar c. fibrous, hydrophobic, nonpolar d. fibrous, polar, nonpolar e. none are true

Q: A major stabilizing factor in the triple helix is a ____ structure such that ____ residues from the three strands stack along the center of the triple helix. a. linear, glu b. linear, gly c. staggered, lys d. staggered, gly e. stacked, pro

Q: Prolyl hydroxylase has all of the following characteristics EXCEPT:a. requires citric acid.b. is activated by Fe2+.c. hydroxylates proline residues in proteins.d. requires molecular oxygen.e. requires -ketoglutarate.

Q: The unique composition of collagen is accommodated in a structure called a(n): a. -pleated sheet. b. triple helix. c. helix-turn-helix motif. d. coiled coils. e. all are true.

Q: Collagen has the following characteristics EXCEPT: a. Tropocollagen is the basic structural unit. b. There is about 33% glycine in collagen. c. Both intermolecular and intramolecular crosslinks help to stabilize the collagen fibrils. d. Modification of prolines occurs prior to collagen synthesis. e. Inextendable fibrous protein are components of connective tissues.

Q: Silk fibers consist of ____ proteins consisting of alternating ____ and ____ or ____ residues. a. fibroin; glycine; proline; leucine b. -keratin; alanine; glycine; serine c. fibroin; glycine; alanine; threonine d. -keratin; cysteine; alanine; proline e. fibroin; glycine; alanine; serine

Q: The "permanent" part of adding wave in hair is primarilydue to: a. rearrangement of hydrogen bonds between hair fibers. b. reestablishment of new ionic interactions between hair fibers. c. breaking and reforming peptide bonds in the hair polypeptides. d. rearrangement of hydrophobic interactions in hair fibers. e. reduction and re-oxidation of disulfide bonds in hair fibers.

Q: -Keratin has all of the following characteristics EXCEPT:a. primary component in hair, claws, fingernails, and horns of animals.b. consists of four helical strands arranged as twisted pairs of two-stranded coiled coils.c. has associated hydrophobic strips on the two coiled coils.d. presence of properly placed polar amino acids help to solubilize -keratin.e. has covalent disulfide bonds to stabilize the structure.

Q: Fibrous proteins contain polypeptide chains ____ producing long fibers or large sheets. a. with an abundance of aromatic amino acids b. with an abundance of hydrophilic amino acids c. organized approximately parallel along a single axis d. with amino acids arranged in a repeating (-a-b-c-d-)n sequence e. all are true

Q: The "Greek Key" topology is composed of ____.a. Adjacent -helices oriented in the same directionb. Adjacent -helices oriented in the opposite directionc. Discreet regions of -sheet oriented in an antiparallel fashiond. Discreet regions of -sheet oriented in an antiparallel fashione. Parallel -sheet structures connected by -helices

Q: Tertiary structure of proteins depends on all of the following EXCEPT:a. protein structure depends on primary structure.b. -helices and -sheets often associate and pack close together.c. secondary structures form whenever possible.d. proteins are stable as a single-layer structure.e. peptide segments between secondary structures are short.

Q: Tertiary structure is defined as: a. the sequence of amino acids. b. the folding of a single polypeptide chain in three-dimensional space. c. hydrogen bonding interactions between adjacent amino acid residues into helical or pleated segments. d. the way in which separate folded monomeric protein subunits associate to form oligomeric proteins. e. all are true.

Q: Which of the following amino acids would generally not be found in an -helix? a. Ala b. His c. Leu d. Ser e. Met

Q: ____ -sheets characteristically distribute hydrophobic side chains on both sides of the sheet, and ____-sheets are usually arranged with all their hydrophobic residues on one side of the sheet.a. Antiparallel, parallelb. Antiparallel, antiparallelc. Parallel, antiparalleld. Parallel, parallele. None of the above

Q: The amino acid residue most likely to be found in a beta turn is: a. glycine. b. alanine. c. valine. d. glutamic acid. e. leucine.

Q: Polylysine is a random coil when the pH is less than 11, while it forms an -helix if the pH is raised to greater than 12. This is because at pH 12: a. the lysine residues are negatively charged which electrostatically stabilizes the helix. b. the positive charges on the lysine residues stabilizes the -helix. c. the lysine residues are neutral which eliminates electrostatic repulsion between the R groups. d. the high concentration of OH ions in solution reduces the electrostatic repulsion between the R-groups. e. the lysine side chain changes configuration with pH.

Q: -Turns in a peptide chain form a tight loop with hydrogen bonding of the carbonyl oxygen with: a. side chain amine of lysine two amino acids down the chain. b. amide proton on the next amino acid down the chain. c. amide proton of the glutamine side chain. d. amide proton of the residue three positions down the chain. e. amide proton of asparagine side chain.

Q: Antiparallel -sheets have:a. sheets that progress from N to C termini in the same direction.b. usually all of their hydrophobic residues on one side of the sheet.c. all hydrophobic residues.d. all hydrophilic residues.e. fibers that can be stretched or extended, but are not flexible.

Q: When the peptide (AEFFLAMEP) forms an -helix, which amino acid residue would be closest to being in the same position on the same face of the helix as is the initial alanine residue?a. F(3)b. A(6)c. E(8)d. P(9)e. L(5)

Q: If the following section of a polypeptide is folded into an -helix, to which amino acid is the carbonyl group of alanine hydrogen bonded?ala-ser-val-asp-glu-leu-glya. serineb. aspartic acidc. glutamic acidd. leucinee. valine

Q: ____ and ____ act as helix breakers due to their unique structure, which fixes the value of the C-N-­C bond angle.a. Histidine, lysineb. Proline, hydroxyprolinec. Arginine, lysined. Serine, threoninee. Tyrosine, serine

Q: In the majority of -helixes, each peptide carbonyl is hydrogen bonded to the peptide NH group ____ residues farther ____ the chain.a. 2, downb. 4, upc. 3, downd. 2, upe. 4, down

Q: Alpha helices are stabilized primarily by:a. hydrogen bonds between the main chain peptide bond component atoms.b. electrostatic interactions between R-groups.c. hydrophobic interactions between the -carbons of the main chain.d. hydrogen bonding between the R-groups.e. hydrophobic interactions between R-groups and the solvent water.

Q: A Ramachandran plot shows:a. the amino acid residues which have the greatest degree of rotational freedom.b. the sterically allowed rotational angles between R groups and -carbons in a peptide.c. the sterically allowed rotational angles between and the amide nitrogen (-N) as well as between and the amide carbonyl carbon (-CO).d. the sterically allowed rotational angles about the amide nitrogen (NH) and CO.e. the amino acid residues that form -helix, -sheet, etc.

Q: Planarity of the peptide bond means that no rotation occurs about the _____ bond while rotation is allowed about the ____ and ____ bonds.e. none of the above

Q: If an aspartic acid residue were present in the interior of a globular protein, it would most likely be _________. a. deprotonated and thus negatively charged b. tightly associated with the R-group of a lysine residue c. react with a cysteine to form a thioester d. react with a serine to form an ester e. none of the above

Q: Secondary and higher orders of structure are determined by all EXCEPT: a. hydrophobic interactions. b. ionic bonds. c. van der Waals forces. d. hydrogen bonds. e. peptide bonds.

Q: Amino acid sequence is: a. primary structure. b. secondary structure. c. tertiary structure. d. quaternary structure. e. regular structure.

Q: All of the information necessary for folding the peptide chain into its "native" structure is contained in the ____ of the peptide. a. amino acid sequence b. amino acid composition c. configuration d. amino acid side chain charges e. all are true