Protein Structure & Function: Amino Acids, Hemoglobin, Myoglobin, Purification Quiz, Exams of Biology

Download Protein Structure & Function: Amino Acids, Hemoglobin, Myoglobin, Purification Quiz and more Exams Biology in PDF only on Docsity! 2023/2024 BIOC 3621 Exam 2 Questions with answers Update • 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 • 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 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: 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 • 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 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. 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 Vmax) observed when [S] is equal to 5KM a. 0.12 Vmax b. 0.38 Vmax c. 0.83 Vmax d. 1.2 Vmax • Many metabolic pathways involve multistep reactions. Consider the pathway: i. E1 E2 E3 E4 • 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 • 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 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 • 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