BIOC_3621_Dewey_Exam_2__1_.docx

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Chamberlain College of Nursing *

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Nov 24, 2024

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BIOC 3621 Exam 2 Best Exam Questions And Answers  Which of the following amino acids would most likely be found on the outside surface of a globular protein? a. L b. R c. P d. I e. V  Which of the following factors tend to destabilize α-helices? a. Cluster of amino acids with bulky R-groups b. Cluster of amino acids with similarly charged R-groups c. Both of these d. Neither of these  The quaternary structure of a protein refers to a. Its amino acid sequence b. The way the protein folds c. The links that stabilize the protein d. The way protein subunits interact with each other  Choose the correct statement a. Replacement of serine causes the greatest effect on protein structure and function b. Replacement such as Lys  Arg causes the greatest effect on protein structure c. Replacement such as Glu  Val causes the greatest effect on protein structure d. Replacement such as Ile  Leu causes the greatest effect on protein structure  The tertiary structure of a protein is usually a result of which of the following interactions? a. Intramolecular hydrogen bonding b. Electrostatic interactions c. Hydrophobic interactions d. All of the above  Which of the following is a mismatched pair regarding the levels or protein structure? a. Primary – amino acid sequence b. Secondary – the ordered 3-dimensional arrangements of a polypeptide backbone c. Tertiary – overall folding of multiple polypeptide chains including all atoms d. Quaternary – association of protein structure  Which of the following statements regarding hemoglobin (Hb) and myoglobin (Mb) is true? a. Tertiary structure is the highest level of structure for Hb b. Mb transports oxygen, while Hb stores it c. Mb is the tetramer, whereas Hb is a single polypeptide chain d. Mb has a single heme group, whereas Hb has 4 heme groups e. Mb and Hb differ only in one amino acid  What is the highest level of organization of myoglobin?

a. Primary structure b. Secondary structure c. Tertiary structure d. Quaternary structure  Proteins that aid in the correct and timely folding of other proteins are called a. Motifs b. Chaperones c. Liposomes d. Cooperative  Which of the following statements about protein structure determination is correct? a. X-ray crystallography is used with liquid samples, while NMR is used with solid samples b. The environment of the protein is close to physiological conditions when it is subjected to x-ray crystallography c. NMR measures chemical shif t of hydrogens within a protein, which x-ray crystallography is based on a diffraction pattern produced by electrons within a protein d. For both NMR and x-ray crystallography, there is no need for mathematical analysis of the data  Why does myoglobin have a histidine that prevents both O 2 and CO from binding perpendicularly to the heme group? a. This increases myoglobin’s affinity for O 2 b. This increases myoglobin’s affinity for CO c. This lessens the difference in myoglobin’s affinity for CO versus O 2 d. This prevents the iron of the heme from being oxidized  Which of the following is true regarding the SDS-PAGE (sodium dodecylsulfate- polyacrylamide gel electrophoresis) method? a. SDS binds to the protein and coats the protein with positive charges b. SDS-PAGE can be used to estimate the molecular weights of proteins c. With SDS-PAGE, the size and shape differences of proteins are eliminated d. All of the above are true e. None of the above are true  In what order would the following globular proteins emerge from a gel filtration column; alcohol dehydrogenase (MW 150,000); β-amylase (MW 200,000); bovine serum albumin (MW 66,000)? a. Bovine serum albumin (first), alcohol dehydrogenase (second), β-amylase (third) b. Alcohol dehydrogenase (first), bovine serum albumin (second), β-amylase (third) c. β-amylase (first), alcohol dehydrogenase (second), bovine serum albumin (third) d. all of the proteins would elute from the column at the same time e. the order of elution cannot be determined from the information provided

 A sample of an unknown peptide was divided into two aliquots. One aliquot was treated with trypsin, the other was treated with cyanogen bromide. Given the following sequences (N- terminal to C-terminal) of the resulting fragments, choose the sequence of the original peptide: i. Trypsin treatment Cyanogen bromide treatment ii. Asn-Thr-Trp-Met-Ile-Lys Gln-Phe iii. Gly-Tyr-Met-Gln-Phe Ile-Lys-Gly-Tyr-Met iv. Gly-Leu-Val-Met-Asp-Arg Gly-Leu-Val-Met a. Asp-Arg-Asn-Thr-Trp-Met b. Gly-Leu-Val-Met-Asp-Arg-Asn-Thr-Trp-Met-Ile-Lys-Gly-Tyr-Met-Gln-Phe c. Asn-Thr-Trp-Met-Ile-Lys-Gly-Tyr-Met-Gln-Phe-Val-Leu-Gly-Met-Ser-Arg d. Met-Val-Ser-Thr-Lys-Leu-Phe-Asn-Glu-Ser-Arg-Val-Ile-Trp-Thr-Leu-Met-Ile e. Leu-Phe-Asn-Glu-Ser-Arg-Met-Val-Ser-Thr-Lys-Val-Ile-Trp-Thr-Leu-Met-Ile f. Gly-Tyr-Met-Gln-Phe-Val-Leu-Gly-Met-Ile-Lys-Gln-Phe-Ser-Arg-Asn-Ile-Trp  Which of the following happens as a protein is purified? a. The percent recovery increases and the specific activity decreases b. The percent recovery decreases and the specific activity increases c. The percent recovery and specific activity both decrease d. The percent recovery and specific activity both increase  In a sample consisting of alanine, arginine, and aspartic acid, which will be eluted last from a cation exchange resin at pH 7? a. Arginine b. Aspartic acid c. Alanine d. All 3 will be eluted at the same time  Ammonium sulfate is useful in protein purification because a. It contains nitrogen and sulfur, both of which occur in proteins b. It is sparingly soluble in water, causing proteins to co-precipitate with it c. Very pure proteins are obtained when it is used d. It increases hydrophobic interactions among proteins, making proteins less soluble and more likely to precipitate  Which of the following methods is used for particle separation of a homogenized sample, in which heavier particles end up in a pellet and less dense particles end up in the supermarket? a. Sonication b. Column chromatography c. Differential centrifugation d. Ion exchange e. None of the above

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 You are studying a protein that is a tetramer, with two subunits that are each 115 amino acids long, and two subunits that are each 320 amino acids long. How many bands would be produced when the protein of interest is subjected to SDS-PAGE? a. 1 b. 2 c. 3 d. 4  In an experiment, you decide to use column chromatography to isolate your protein of interest. Your protein binds specifically to boronic acid, so you use a stationary phase made of boronic acid-agarose resin. Which type of column chromatography are you using? a. Gel filtration b. Affinity chromatography c. Cation or anion exchange d. Isoelectric focusing e. All of these  Which of the following is true for both ELISA and Western blotting? a. ELISA and Western blotting use only primary antibodies b. ELISA and Western blotting use only secondary antibodies c. ELISA and Western blotting are techniques used to detect nucleic acids d. For both ELISA and Western blotting, the first step is gel electrophoresis, followed by transfer of the samples to a membrane  If a protein with the sequence PQRKYPIG is treated with trypsin, what will the products be? a. PQR KYPIG b. PDRK YPIG c. PQR K YPIG d. PQ R KPIG  Using this reaction, the rate of breakdown of the enzyme-substrate complex can be described by the expression:  24. a. K 1 ([E t ]-[ES]) b. K 1 ([E t ]-[ES])[S] c. K 2 [ES] d. K -1 [ES] + k2 [ES] e. K -1 [ES]

 Which of the following is most directly related to the speed of a reaction? a. The temperature b. The ΔG 0 of the reaction c. The ΔG of the reaction d. The ΔG 0‡ of the reaction e. None of the above  Which of the following is false regarding the Michaelis constant? a. K M is a measure of how tightly the substrate is bound to the enzyme b. K M determines the V max of an enzymatic reaction c. K M is derived from the rate constants of the individual steps in the catalytic scheme d. K M is equal to the substrate concentration that yields a velocity of ½V max  Hexokinase is an enzyme that can use either glucose or fructose as its substrate. The K M values of hexokinase are 0.15mM for glucose and 1.5mM for fructose. Which is the preferred substrate for this enzyme? a. Glucose b. Fructose c. There is no preference of hexokinase for either substrate d. You cannot tell from the data given  Use the following figure to answer Questions 16 and 17:   “Hindrate” is an inhibitor of triose phosphate isomerase. When it is added to cells at a concentration of 0.1nM, the enzyme’s K M for the substrate is unchanged, but the apparent V max is altered to 50nM/sec. Which of the following correctly describes “hindrate”? a. It is a competitive inhibitor b. It is an uncompetitive inhibitor c. It is a noncompetitive inhibitor d. It is an irreversible inhibitor  In the graph, which line best represents the Lineweaver-Burk plot in the presence of hindrate? a. A

b. B c. C d. D e. E  Which of the following is false? a. Most enzymes are globular proteins b. The transition state of an enzyme-catalyzed reaction determines the velocity of the reaction c. Enzymes are highly specific, being able to distinguish stereoisomers of a given compound d. Catalysts work by lowering the free energy of the reactants  If an inhibitor can bind to the free enzyme-(E), but it cannot bind to the enzyme- substrate complex (ES), what kind of inhibition is being displayed? a. Competitive b. Uncompetitive c. Noncompetitive d. Mixed noncompetitive  Which of the following is true? a. The order of a reaction can always be determined from the balanced equation for this reaction b. Enzymes primarily use covalent interactions in binding substrates c. The substrate will only bind to the enzyme when the shapes fit together rigidly d. The transition state of an enzyme-catalyzed reaction has higher free energy than either the substrate or the products  Which of the following accurately describes the induced-fit model of substrate binding to enzymes? a. There is aggregation of several enzyme molecules when the substrate binds b. There is a conformational change in the enzyme when the substrate binds c. The substrate changes its conformation to fit the active site d. The substrate fits into the active site like a key fits into a lock  According to traditional Michaelis-Menton kinetics, an enzyme will display order kinetics when the substrate concentration is low; whereas, when an enzyme is saturated with substrates, it will display order kinetics a. Zero, First b. First, Second c. Second, Zero

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d. First, Zero e. This cannot be determined without actual data  For an enzyme that displays Michaelis-Menton kinetics, what is the reaction velocity, V (as a percentage of V max ) observed when [S] is equal to 5K M a. 0.12 V max b. 0.38 V max c. 0.83 V max d. 1.2 V max  Many metabolic pathways involve multistep reactions. Consider the pathway: i. E 1 E 2 E 3 E 4  A  B  C  D  F (final product) a. The product of the final reaction (F) interacting with E1 b. F interacting with an allosteric site on E4 c. B interacting with an allosteric site on E1 d. All of the intermediates (B, C, and D) interacting with E1  The active site of an enzyme a. Is frequently located in a cleft of the enzyme b. Is the portion of the enzyme to which the substrate binds c. Contains the reactive groups that catalyze the reaction d. May contain asymmetric binding sites for stereospecificity e. All of the above  Homotrophic effects for allosteric enzymes involve a. Different molecules binding to the same site in an enzyme b. Different molecules binding to different sites in the same enzyme c. The same molecule binding to different sites in the same enzyme d. All of these are homotrophic effects  Which of the following is true? a. Michaelis-Menton kinetics describe the reactions of allosteric enzymes b. Allosteric enzymes have a hyperbolic plot of reaction rate vs substrate concentration c. Substrates, activators, and inhibitors all compete for the same binding site on enzymes d. Allosteric enzymes have multiple subunits e. Allosteric enzymes are rarely important in the regulation of metabolic pathways  When considering the differences between the concerted model and the sequential model for allosteric enzymes, which of the following is false? a. In the concerted model, all of the subunits of the enzyme change conformation simultaneously

b. The sequential model is explained better by the induced-fit model of substrate binding, whereas the concerted model focuses on perturbing the equilibrium between the T and R forms c. Negative cooperativity can be explained by the concerted model d. The sequential model allows for different subunits of the same enzyme to be in different conformations  Zymogens are a. Inactive precursors of enzymes which can be activated by the irreversible cleavage of covalent bonds b. Inactive forms of enzymes that require phosphorylation by a kinase to become active c. Allosteric enzymes that are always in the R state d. Allosteric enzymes that are always in the T state  Phosphorylation of enzymes a. Always increases enzyme activity b. Usually takes place on serine, threonine, and tyrosine residues c. Does not require ATP d. Is typically catalyzed by phosphatases  Taking into consideration the most common chemical reactions involved in enzyme mechanisms, what would likely be the role of a serine in the active site of chymotrypsin? a. A Lewis acid b. A metal ion c. An electrophile d. A nucleophile  In the presence of CTP, would the control curve be shifted to a or b? Does this represent activation or inhibition? a. A, activation b. A, inhibition c. B, activation d. B, inhibition  In the presence of ATP, would the control curve be shifted to a or b? Does this represent activation or inhibition? a. A, activation b. A, inhibition c. B, activation

d. B, inhibition  According to the concerted model for allosteric enzymes, an allosteric activation (? Page cut off) a. Favors the tight (taut) form of the enzyme b. Favors the relaxed form of the enzyme c. Can only bind the substrate if the enzyme is already bound d. Can only bind the substrate if the enzyme is not already bound  All of the following are examples of cofactors for enzymes except a. Vitamin B 6 b. Zn +2 c. Fe +3 d. O 2 e. NAD +  Which of the following does NOT contribute to the sigmoidal stage of the curve for allosteric enzyme binding to substrate? a. Higher favorability of the T form of the enzyme when it is unbound to substrate b. Higher favorability of the R form of the enzyme when it is bound to substrate c. More affinity for substrate when enzyme is in the R form d. Higher “c” value e. Higher “L” value  Which of the following are membrane lipids?  1. Cholesterol 2. Glycolipids 3. Phosphoglycerides 4. Sphingolipids 5.Triscy (?page cut off) a. 1, 2, 3, and 4 b. 1, 3, 4, and 5 c. 1, 3, and 4 d. 1, 2, 3, 4, and 5  Which of the following four fatty acids has the lowest melting point?  CH 3 CH 2 CH 2 CH 2 CH 2 COOH  CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH  CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 COOH  CH 3 CH=CHCH 2 CH 2 COOH a. 1 b. 2 c. 3 d. 4  Which of the following is true ?

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a. Trans double bonds in fatty acids tend to increase membrane fluidity b. Unsaturated fatty acids usually have trans double bonds c. Most fatty acids have an odd number of carbons d. Cholesterol tends to decrease membrane ???  Which of the following lipid molecules possess a different fundamental structural makeup from the others? a. Fatty acids b. Cholesterol c. Triglycerides d. Sphingolipids e. Glycolipids  Cell membranes typically display asymmetry. What does this mean? a. The two leaflets of the bilayer contain different collections of lipids and proteins b. The fatty acyl chain on the first carbon (C-1) of a membrane lipid is usually different from that on the third carbon (C-3) c. Only one stereoisomer is ever seen at the chiral C-2 (carbon at position 2) of the glycerol residue in a lipid membrane d. Membrane lipids only have cis double bonds, never trans  Which group of lipids does the structure to the right belong to a. Sphingolipids b. Phosphoacylgylcerols c. Triacylglycerols d. Glycolipids e. Steroids  Which group of lipids does the structure to the right belong to? a. Sphingolipids b. Phosphoacylgylcerols c. Triacylglycerols d. Glycolipids e. Steroids  Energy is indirectly used to co-transport hydrogen ions and glucose sugar across the cell membrane, against the concentration gradient of the glucose. This scenario describes a. Simple diffusion b. Facilitated diffusion c. Primary active transport

d. Secondary active transport e. Endocytosis  Membrane proteins a. Are sometimes covalently attached to lipid molecules b. Are sometimes covalently attached to carbohydrate molecules c. Are composed of the same 20 amino acids found in soluble proteins d. Diffuse laterally in the membrane unless they are anchored e. Have all of the properties listed above  Which of the following lipid-soluble vitamins is correctly paired with its primary function a. Vitamin D – vision b. Vitamin K – blood-clotting c. Vitamin E – calcium and phosphorus metabolism d. Vitamin A – antioxidant  These two families of compounds are derived from arachidonic acid and have physiologically relevant functions in the body related to immunity and response to inflammation a. Triacylglycerols and fatty acids b. Phosphoacylgycerols and steroids c. Steroids and leukotrienes d. Leukotrienes and prostaglandins e. Prostaglandins and sphingolipids

BIOC_3621_Dewey_Exam_2__1_.docx

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