Protein Structure & Function: Amino Acids, Quaternary Structure, Hemoglobin, Myoglobin, Exams of Nursing

Download Protein Structure & Function: Amino Acids, Quaternary Structure, Hemoglobin, Myoglobin and more Exams Nursing in PDF only on Docsity! BIOl 3621 Exam 2 Questions with answers Update 2023/2024 guaranteed success • 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 O2 and CO from binding perpendicularly to the heme group? a. This increases myoglobin’s affinity for O2 b. This increases myoglobin’s affinity for CO c. This lessens the difference in myoglobin’s affinity for CO versus O2 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 • 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. K1 ([Et]-[ES]) b. K1 ([Et]-[ES])[S] c. K2 [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 ΔG0 of the reaction c. The ΔG of the reaction d. The ΔG0‡ of the reaction e. None of the above • Which of the following is false regarding the Michaelis constant? a. KM is a measure of how tightly the substrate is bound to the enzyme b. KM determines the Vmax of an enzymatic reaction c. KM is derived from the rate constants of the individual steps in the catalytic scheme d. KM is equal to the substrate concentration that yields a velocity of ½Vmax • Hexokinase is an enzyme that can use either glucose or fructose as its substrate. The KM 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 KM for the substrate is unchanged, but the apparent Vmax 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 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 B6 b. Zn+2 c. Fe+3 d. O2 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? • CH3CH2CH2CH2CH2COOH • CH3CH2CH2CH2CH2CH2CH2CH2CH2COOH • CH3CH2CH2CH2CH2CH2CH2COOH • CH3CH=CHCH2CH2COOH a. 1 b. 2 c. 3 d. 4 • Which of the following is true? 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