Exam 2 MC Question Bank Flashcards
Sequence the following events with regards to His12 and His119 working together to catalyze the RNAase A reaction.
A. His119 acts as a base by deprotonating a water molecule from the solvent to activate it for hydrolysis of the cyclic nucleotide intermediate
B. His12 acts a a base catalyst to remove a proton from the 2’-OH of the RNA phosphorous atom nearby
C. His12 acts as an acid and protonates the oxygen bond to the phosphorous atom
D. His119 acids as an acid catalyst and donates a proton to the leaving group, oxygen, to promote bond breakage
C
What is the main product of glycogen degradation?
What is the main product of glycogen degradation?
A. Fructose-6-Phosphate
B. Glucose-1-Phosphate
C. Glucose-6-Phosphate
D. Fructose-1,6-biphosphate
E. Fructose-6-phosphate
B.
Admin comment: You may want to specific “initial product” or “product of initial steps” or something like that. Some might consider the mutase to be part of “glycogen degradation”
Which of the following compounds does not capture the release of energy for use? A. H3CCOSCH3 B. Polysaccharides C. Some bullshit structure D. Reduced Coenzymes (NADH,FADH2,QH2
B.
What is the primary function of Phosphoglucose Isomerase?
A. To convert F6P to FBP
B. To aid Triose Phosphate Isomerase to convert an aldose to a ketose.
C. To covert G6P to F6P
D. This is not an enzyme we have studied.
E. To help GAPDH help convert GAP to 1,3-BPG
C
Competitive inhibitors do all of the following except: A. bind to the free enzyme B. resemble the substrate C. increase the KMapp D. bind to the enzyme complex E. Have a reversible KI
D
Which is NOT true as to why glucose is stored as glycogen?
A. Glucose can be forced into different pathways while glycogen is not.
B. Glucose is more inert than Glycogen
C. Increase of Glucose concentration affects the osmolarity environment.
D. Glycogen is a polymer of glucose.
B
Which implication of thermodynamics for metabolic pathways is true?
A. Metabolic pathways are reversible in the cell
B. Every metabolic pathway has two committed steps
C. Catabolic and anabolic pathways differ
D. All reactions in the metabolic pathway have a positive delta G
C
Which of the following responses includes the appropriate enzyme and thermodynamic characteristic of the committed step in glycolysis?
A. Phosphofructokinase-1, irreversible
B. Hexokinase, reversible
C. Aldolase, irreversible
D. Triose Phosphate Isomerase, irreversible
E. Phosphoglycerate Kinase, reversible
A.
What enzyme catalyzes the reaction of Fructose1-6-biphosphate to glyceraldehyde 3-phosphate + dihydroxyacetone phosphate? A. Hexokinase B. glucose-6-phosphate C. Phosphoglucomutase D. alodase E. pyruvate kinase
D
You are trying to develop a drug to inhibit an enzyme by competitive inhibition. Based on experimentally the most effective inhibitors, what molecule should you strategize to model the structure of the drug to resemble, in order to have the most effective inhibition?
A. The reaction’s substrate
B. The reaction’s transition-state intermediate
C. The reaction’s product
D. A molecule that binds to the enzyme outside of the activation site that causes an allosteric conformation change
B (Comment says answer is A)
Which of the following sugars can be used by hexokinase within muscle cells during glycolysis? A. Galactose B. Mannose C. Fructose D. Lactose E. Dextrose
C. Hexokinase in muscle cells can use fructose as a substrate (a substitution for glucose) during glycolysis. Fructose becomes phosphorylated by hexokinase to make fructose 6 phosphate, a good substrate for PFK 1. Fructose 6 phosphate will then be phosphorylated a second time to continue in the glycolysis process.
The following is a Double Reciprocal Plot (intersect at y-axis; same Vmax, different KM) where an inhibitor is present and is not present in an enzyme. Which kind of inhibitor is present and why?
A. Uncompetitive Inhibitor, because Km increases with the inhibitor present and Vmax is not changed.
B. Competitive Inhibitor, because Km increases with the inhibitor present and Vmax is not changed.
C. Noncompetitive Inhibitor, because Km increases with the inhibitor present and Vmax is not changed.
D. Competitive Inhibitor, because Km decreases with the inhibitor present and Vmax is not changed.
E. Uncompetitive Inhibitor, because Km decreases with the inhibitor present and Vmax is not changed.
B
An individual is resting on the couch and has a high amount of ATP available. Will glycolysis continue to occur if the person remains sedentary? Why or why not?
A. Yes, hexokinase will continue to bring in more glycogen to add to the ATP stores
B. Yes, pyruvate dehydrogenase is overly active in sedentary individuals
C. No, the high amounts of ATP will inhibit phosphofructokinase activity
D. No, the high amounts of ATP will inhibit glycogen synthase
E. Yes, ATP constantly disassociates on its own so it must constantly be replenished
C
In Glycolysis there are ten steps and four of them use Kinases. Which four steps use Kinases and what ion do these Kinases require? A. 3, 6, 8, and 9; K+ B. 1, 3, 7, and 10; Mg2+ C. 3, 6, 8, and 9; Fe2+ D. 1, 3, 7, and 10; Ca2+ E. 3, 6, 8, and 9; Na+
B
Which of the following is NOT a coenzyme? A. CoA B. Mg2+ C. NADH D. FADH2 E. NAD+
B
In the catalytic mechanism of lysozyme, the unusual pKa of glutamate 35 allows it to act as a ________ by ________________.
A. Base catalyst; de-protonating the oxygen-1 atom that is part of the beta 1-4 linkage connecting the D and E rings
B. Acid catalyst; protonating the oxygen-1 atom that is part of the beta 1-4 linkage connecting the D and E rings
C. Both an acid and a base catalyst; protonating the oxygen-1 atom that is a part of the beta 1-4 linkage and later in the mechanism de-protonating the oxygen-1 atom to give the final product
D. None of the above
B
Which of the following is true about the Pentose Phosphate Pathway?
I.The Pentose Phosphate Pathway supplies Ribose-5-phosphate to cells through the synthesis of Glucose-6-phosphate.
II.Synthesis of Ribose-5-Phosphate is required for metabolism of amino acids.
III.The Pentose Phosphate Pathway is reliant upon the availability of NADPH, and is inhibited by a lack of this molecule.
IV. The Pentose Phosphate Pathway occurs in tissues that synthesize fatty acids, such as the liver and adipose tissue.
V.Erythrocytes use the oxidized form of NADP+ as a result of this pathway to maintain reduced iron in hemoglobin.
A. I, II, III, V
B. I, III, IV
C. I, II, IV
D. I, III, V
E. All of the above
C
Enzymes help reactions reach equilibrium more quickly by
A. increasing activation energy
B. keeping activation energy constant
C. enzymes have no control over activation energy
D. decreasing activation energy
E. none of the above
D
Which of the following is true regarding enzymatic catalysis?
A. Enzymes have no effect on overall energy of activation and use structural changes to increase the rate of reaction
B. The decrease in stability during transient bond formation allows for decomposition of a molecule which increases the rate of reaction
C. Hydroxyl, sulfhydryl, amino, and imidazole are all important biological nucleophiles for metabolic reactions within the body
D. Metal ion catalysis involves the binding of 1st row transition state metals to the side chains of the enzyme to prevent binding to the active site
E. When binding sites with low specificity are used, correct positioning of reacting groups occurs, ultimately increasing degrees of freedom and allowing for easier degradation of enzyme-substrate complex
C
An enzyme has a KM of 12mM in the absence of a competitive inhibitor and a KMapp of 18mM in the presence of 4mM of the inhibitor. Calculate KI. A. KI=10.25mM B. KI=8.00mM C. KI=14.10mM D. KI=16.00mM E. KI=7.75mM
B. KI is equal to [Inhibitor]/(a-1), where a= KMapp/KM. So, a= 18mM/12mM= 1.5. KI= 4mM/(1.5-1) = 8.00mM.
This Lineweaver-Burk graph was produced by enzyme A (dotted line) and enzyme A + an inhibitor (solid line) (PARALLEL LINES). Which of the following statements is correct?
A. The ΔG of the inhibited reaction is higher that than of the uninhibited reaction. Adding more substrate would cause the effect of the inhibitor to lessen.
B. According to apparent Km values, the enzyme has a greater affinity for the substrate without the inhibitor present. The inhibitor used is uncompetitive.
C. Adding more substrate to the reaction would have no effect on the inhibitor’s activity. The inhibitor is binding to the same site as the substrate.
D. The y-intercept is equal to α’/Vmax where α’ is 1 when there is no inhibitor. The inhibitor is causing an allosteric change to the enzyme’s structure.
E. Because the inhibitor is noncompetitive, adding more substrate to the reaction would not
E have an effect on the inhibitor’s activity. The ΔG of the inhibited reaction is higher than that
of the uninhibited reaction.
D
In what form is a Glucose derivative transferred to in order to recycle carbon atoms for further use in Glycolysis (not from the very beginning of Glycolysis)? A. G6P B. Glycogen C. RuBisCO D. Xu5P E. GAP
D
Which of the following is true about the net glycolysis reaction? I. One molecule of glucose is consumed II. Four molecules of ATP are created III. Two molecules of NADH are created IV. Three molecules of pyruvate are produced A. III & IV B. II & IV C. I, II, & IV D. I & III E. II, III & IV
D
Aldehyde dehydrogenase is an enzyme which oxidizes Acetaldehyde produced from the oxidation of ethanol. In many East Asian populations, a genetic mutation has resulted in a nearly inactive form of Aldehyde dehydrogenase. Compared to a normal enzyme, one would expect the inactive enzyme to have which of the following? A. Higher Km. Higher Kcat B. Higher Km. Lower Kcat C. Lower Km. Higher Kcat D. Lower Km. Lower Kcat
B
Which of the following steps are irreversible in glycolysis?
1. Fructose 6 phosphate to fructose 1,6 biphosphate 2. Glucose to Glucose 6 phosphate
3. Glucose 6 phosphate to fructose 6 phosphate
4. Phosphoenolpyruvate to pyruvate
A. 1, 2, 3
B. 1, 2
C. 1, 4
D. 3, 4
E. 1, 2, 4
E
Which of the following would serve to allosterically inhibit the rate of glycolysis? A. Increased fructose B. Decreased ATP C. Increased glucose D. Increased oxygen E. Increased ATP
E
Which of the following are considered somewhat universal observations about metabolic pathways?
I. Catabolic and anabolic reactions cannot run completely in reverse
II. They tend to be irreversible in vivo
III. There are no committed steps for the pathways
IV. They have a committed step that ensures the substrate is moving in one overall direction
V. Reactions can always run completely in reverse
A. III & V
B. I, II, & IV
C. IV only
D. II & IV
E. I & V
B
Which of the following is true about the monosaccharides D-glucose and D-fructose?
A. For glucose, carbon 2 is oxidized to a ketone and carbon 1 on fructose is oxidized to an aldehyde
B. For glucose, carbon 1 is oxidized to a ketone and carbon 2 on fructose is oxidized to an aldehyde
C. For glucose, carbon 2 is oxidized to an aldehyde and carbon 1 on fructose is oxidized to a ketone
D. For glucose, carbon 1 is oxidized to an aldehyde and carbon 2 on fructose is oxidized to a ketone
E. Glucose is referred to as a ketose and fructose is referred to as an aldose
D
Does anaerobic glycolysis produce ATP faster than aerobic glycolysis? Why?
A. False, aerobic glycolysis is more thermodynamically favored, therefore it produces ATP at a faster rate
B. True, anaerobic glycolysis is more thermodynamically favored, therefore it produces ATP at a faster rate
C. False, aerobic glycolysis has high concentrations of reactants and products, therefore it produces ATP at a faster rate
D. True, anaerobic glycolysis produces ATP at a faster rate because anaerobic glycolysis occurs takes place in muscle tissue at a higher temperature
B? Outten wrote lots of comments on this one. Basically take this with a grain of salt.
Which of the following mechanisms of catalysis are exhibited in the catalytic mechanisms of Serine Proteases? I. Acid-Base Catalysis II. Covalent Catalysis III. Metal Ion Catalysis IV. Proximity Effect/Orientation V. Transition State Stabilization A. I, II & V B. I & II C. I, IV, & V D. II, III & V E. I, II & IV
A.
First molecule has OH in the trans configuration to CH2OH, second has OH in the cis configuration. The 2nd molecule is an example of: A. Alpha-anomer B. Epimer C. Beta-anomer D. Enantiomer
C.
Admin Comment: The two molecules are also epimers of each other so that answer could arguably be correct.
In the lysozyme mechanism, which step produces a covalent intermediate?
A. Aspartate52 performing a nucleophilic attack on C1 of the oxonium ion transition state.
B. Glutamate35 performing a nucleophilic attack on C1 of the oxonium ion intermediate.
C. Aspartate52 protonating the O1 atom that is past of the beta 1,4- linkage connecting D/E rings.
D. Glutamate35 protonating the O1 atom that is past of the beta 1,4- linkage connecting D/E rings.
E. None of the above.
A
The interconversion of glycogen to glucose begins in the postabsorptive phase in order for the body to maintain its strict glucose levels in the blood, producing glucose-1-phosphate to be converted to glucose-6-phosphate. Likewise, upon the introduction of lactose, enzymes can degrade the disaccharide, producing a galactose molecule which can be used to produce glucose-1-phosphate as well. Which of the following serves as the intermediate of this pathway between galactose and glucose-1-phosphate, allowing it to inevitably be metabolized by glycolysis? A. UDP-glucose B. UDP-galactose C. galactose-1-phosphate D. glucose-1,6-bisphosphate E. fructose-6-phosphate
C
Which step (and enzyme) of glycolysis is the irreversible, "committed" step of the pathway? A. Step 3: Hexokinase B. Step 10: Pyruvate Kinase C. Step 1: Hexokinase D. Step 1: Phosphofructokinase (PFK-1) E. Step 3: Phosphofructokinase (PFK-1)
E
Which of the following is TRUE concerning enzymes and the effects of enzymes on a reaction:
I. Enzymes can decrease the overall Gibbs Free Energy of the reaction
II. Enzymes decrease the activation energy of the reaction
III. Enzymes have specificity and participate in a select few reactions
IV. Enzymes cannot be subjugated to regulation once it has begun acting in a metabolic pathway
A. I & IV
B. II & III
C. I, II, & III
D. I, III, & IV
B
In skin cells, which reaction would Ribulose-5-phosphate be most likely to undergo?
A. An epimerization reaction, generating Xylulose-5-phosphate
B. An isomerization reaction, generating Xylulose-5-phosphate
C. An epimerization reaction, generating Ribose-5-phosphate
D. An isomerization reaction, generating Ribose-5-phosphate
E. It would not undergo any of these reactions in a skin cell
D. Skin cells are rapidly dividing cells, so ribose-5-phosphate would be most likely to found in these cells since it can be used as a precursor for nucleotides. In order for ribulose- 5-phosphate to be turned into ribose-5-phosphate it must undergo an isomerization reaction. If it were to undergo epimerization it would end up as xylulose-5-phosphate.
Phosphofructokinase is a major control point in the glycolysis process. Which statement below is false regarding its structure/function?
A. PFK is a homo-tetrameric enzyme
B. ATP functions as both a substrate and an allosteric inhibitor of PFK
C. PFK-1 is the first metabolically irreversible step in glycolysis
D. PFK is found in both active (R) and inactive (T) states
C
Glycogen phosphorylase (GP) and glycogen synthase (GS) control glycogen metabolism and storage in liver and muscle cells. Mutations in these enzymes and similar enzymes can lead to all of the following conditions except:
A. Enlarged liver
B. Biliary Atresia
C. Hypoglycemia
D. Her’s disease
E. None of the above, all are possible conditions
B
What alcohol, catalyzed by Alcohol Dehydrogenase, is converted to formaldehyde in the body, which can have detrimental effects to the optical nerve and in some cases cause fatalities? A. Ethanol B. Butanol C. Methanol D. Propanol E. cyclohexanol
C
Which of these catalytic mechanisms is NOT utilized by Serine Proteases?
A. Covalent catalysis
B. Metal ion catalysis
C. Preferential binding to transition state
D. Acid/base catalysis
E. Electrostatic interactions
B
Glucose is the major metabolic fuel in the body and mammals maintain their own blood glucose levels.
How does the body respond to maintain blood glucose levels during fasting or starvation within the body?
A. Body first breaks down stored glycogen to release glucose
B. During phase 3-4, via gluconeogenesis the liver begins to synthesize new glucose from non- carbohydrate sources
C. The body can not maintain blood glucose levels during starvation or fasting
D. both A and B
E. none of the above
D
Glucose is the main sugar that is used to begin glycolysis. There are, however, other sugars that can be used by glycolysis to create the necessary products at different steps to keep glycolysis moving forward. The following sugars that can be used aside from glucose are: mannose, fructose, and galactose.
Which answer has the correct product that the sugars make in glycolysis and where the body gets them from?
A. Mannose (muscle): G6P, F6P
Fructose (liver, dietary polysaccharides): F6P Galactose (milk): GAP
B. Mannose (muscle): F6P
Fructose (liver, dietary polysaccharides): GAP, F6P Galactose (milk): G6P
C. Mannose (liver): G6P, F6P
Fructose (muscle): F6P
Galactose (dietary fats): GAP
D. Mannose(dietary polysaccharides): F6P
Fructose (liver, muscle): GAP, F6P
Galactose (milk): G6P
E. Mannose (dietary polysaccharides): GAP
Fructose (liver, muscle): F6P, GAP
Galactose (dietary fats): F6P
DMannose: derived from the dietary polysaccharides and can only be phosphorated by hexokinase at C6 following this reaction chain to generate F6P (that is used in glycolysis):
manose –hexokinase–> manose-6-phosephate —phosohpmase isomerase–> fructose-6-phosphsate (F6P)
Fructose: extracted from the muscle and liver of the body. It can be directly phosphorylated by hexokinase (similarly to mannose as stated above) when derived from the muscle to make F6P. When fructose is used from the liver it is oxidized to make more GAP to be consumed in constant forward reaction with GAPDH
Galactose: extracted from milk; galactose is phosphorylated at the C1 end and a UDP is transferred from UDP-Glu to Galactose (makes UDP-Galactose). An epimerase then converts it to UDP-Glu and once the Glucose 1 phosphate is released it makes G6P which helps drive forward glycolysis.
Why is triose phosphate isomerase important in the process of glycolysis?
A. This enzyme converts a ketose into an aldose, and this aldose will only proceed through the rest of the pathway.
B. It is an enzyme that catalyzes an irreversible reaction, moving the glycolytic pathway forward instead of backwards.
C. It catalyzes the transfer of a phosphoryl group from ATP to glucose.
A
Match the following Lineweaver-Burke plots with the correct inhibitor description:
Graph 1: (PARALLEL LINES)
Graph 2: (INTERSECT AT Y-AXIS)
Graph 3: (INTERSECT TO THE LEFT OF Y-AXIS)
A. Graph 1 is Competitive inhibitor, Graph 2 is Uncompetitive inhibitor, and Graph 3 is Noncompetitive inhibitor.
B. Graph 1 is Noncompetitive inhibitor, Graph 2 is Uncompetitive inhibitor, and Graph 3 is Competitive inhibitor.
C. Graph 1 is Uncompetitive inhibitor, Graph 2 is Noncompetitive inhibitor, and Graph 3 is Competitive inhibitor.
D. Graph 1 is Uncompetitive inhibitor, Graph 2 is Competitive inhibitor, and Graph 3 is Noncompetitive inhibitor.
D
Which of the following inhibits binding of the substrate? A. Mixed Inhibitor B. Noncompetitive Inhibitor C. Competitive Inhibitor D. Uncompetitive Inhibitor
C
The enzyme pyruvate decarboxylase uses what as a cofactor during alcoholic fermentation? A. Zinc B. NADPH C. Heme D. Thiamine Pyrophosphate E. Pyridoxal phosphate
D
Alpha-glucosidase is an enzyme found in the small intestine that breaks down starch and disaccharides to glucose. In traditional Indian medicine, the Cymbopogon martinii plant (CM) is used to treat diabetes mellitus due to its ability to inhibit this enzyme. These are the experimental results of a study of the activity of alpha-glucosidase at varying concentrations of maltose with different added concentrations of CM extract. Based on this Lineweaver- Burk plot, what type of inhibitor is CM? (INTERSECT TO THE LEFT OF Y-AXIS) A. Competitive B. Uncompetitive C. Noncompetitive D. None of these E. Cannot be determined
C.
Which of the following correctly describes a major difference between NADPH and NADH?
A. NADPH is used mostly in catabolic reactions and NADH is used mostly in catabolic reactions
B. NADPH is used mostly in catabolic reactions while NADH is used mostly in anabolic reactions
C. NADPH is used mostly in anabolic reactions while NADH is used mostly in catabolic reactions
D. NADPH is used mostly in anabolic reactions while NADH is used mostly in anabolic reactions
C. NADH is known for its role in cellular respiration (catabolic), while NADPH is known for its role in photosynthesis (anabolic)
