Quiz
BT2
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Perguntas do quiz (157)
1Which statement is false regarding ΔG°’ of a reaction?
- Afor a reaction at equilibrium under standard conditions, ΔG°’ = 0.
- Bfor a reaction that releases energy under standard conditions, ΔG°’ < 0
- Cfor a reaction which requires an input of energy under standard conditions, ΔG°’ > 0.
- Da reaction that has ΔG°’ < 0 is considered a spontaneous or favorable reaction.
- Eenzymes can lower the ΔG°’ of a reaction
2The following is a reversible enzyme catalyzed reaction: A + B = C. If you add enzyme to a solution containing only C, what would happen?
- ANothing, because the enzyme reduces the standard free energy change for the reaction
- BNothing, because the product is already formed
- CNothing, because product inhibits the enzyme
- DNothing, the reaction is at equilibrium
- EThe reaction would proceed backwards until reaching equilibrium
3A first order chemical reaction has an equilibrium constant of 1. If you add an enzyme that catalyzes this reaction, how would this effect the rate constants for the forward and reverse reactions?
- AThey would be larger
- BThey would be smaller
- CThey would be the same
- DThey would depend on the reaction
- Eyou cannot tell from only these data
4A first order chemical reaction has an equilibrium constant of 1. If you speed up the forward and reverse reactions equally, how would this effect the equilibrium constant?
- AIt would be larger
- BIt would be smaller
- CIt would be the same
- DIt would depend on the reaction
- Eyou cannot tell from only these data
5In an enzyme mediated reaction with saturating amounts of substrate, what is the most direct way to increase the reaction rate?
- Aadd extra co-factor
- Bnone of these
- Cadd inhibitor
- Dadd more enzyme
- Eadd more substrate
6If an enzyme speeds up the forward direction of a reaction, which of the following
must also be true- AIt lowers the free energy change associated with the reaction
- BIt raises the free energy change associated with the reaction
- CIt lowers the activation energy of the reaction only in the forward direction
- DIt raises the activation energy of the reaction only in the forward direction
- EIt must also speed up the reverse direction of the reaction
7Which of the following is true about enzymes?
- Aenzymes work by lowering the free energy of the reaction they catalyze
- Benzymes cannot catalyze a reaction for which delta G0 is positive
- Cenzymes cannot catalyze a reaction for which delta G0 is negative
- Denzymes can only catalyze a reaction that is kinetically favored
- Eenzymes work by lowering the activation energy for the reaction they catalyze
8Which of the following statements about enzymes is correct?
- Aenzymes change the free energy of substrates and products
- Benzymes change both reaction rates and equilibrium constants
- Cenzymes speed up both forward and reverse reactions
- Denzymes do not change the transition state's free energy
9The induced fit model for enzyme catalysis is distinguished from the lock and key model in that:
- Ain the induced fit model, the enzyme binds the transition state
- Bin the lock and key model, the enzyme binds the transition state
- Cin the induced fit model, the enzyme binds the substrate
- Din the lock and key model, the enzyme binds the substrate
- Ein the induced fit model, the enzyme structure is altered by the substrate
- Fin the lock and key model, the enzyme structure is altered by the substrate
10Which is bound most tightly by enzymes?
- Atheir co-substrate(s)
- Btheir substrate(s)
- Ctheir product(s)
- Dtheir transition state intermediate(s)
11The following reaction is that of alcohol dehydrogenase (ADH), an enzyme active in the liver. Which of the following describes most accurately all of the potential substrate(s) for this enzyme?
- AEthanol
- BAcetaldehyde
- CNAD+
- DNADH
- EAll of these are potential substrates
12Which of the following is NOT a way in which enzymes stabilize a transition state?
- Aincreasing the temperature of the active site
- Bgeneral acid/base catalysis
- Cuse of a metal ion co-factor
- Dcatalysis by approximation
- Ecovalent catalysis
13Which kinetic parameter would change if you increase the amount of enzyme in a reaction?
- AKcat
- BKm
- CKi
- DVmax
14For a Michaelis-Menten enzyme, if you know KM, you know:
- A[S] at one-half Vmax
- BVmax at infinite [S]
- Ck2
- Dkcat if you know [S]
- Enone of these
15Which of the following is true about KM?
- AKM approximates the equilibrium constant for substrate binding
- BKM is a function of Mickaelis-Menten rate constants
- CKM has units of molarity
- DKM for a particular enzyme tells you about functionally relevant substrate concentrations
- EAll of these are true
16When Km increases in any enzyme reaction, the
- Aaffinity of enzyme for substrate increases
- Baffinity of enzyme for substrate decreases
- Caffinity of enzyme for substrate is unchanged
- DVmax always decreases
- Enone of the above
17The “T” and “R” states of the MWC model are associated with ____ and ____ values of KM, respectively?
- AFaster, slower
- BSlower, faster
- CHigher, lower
- DLower, higher
- EThe same
18Which of the following is true about Km in the Michaelis-Menten model?
- Ait is equal to (k-1+k2)/k1
- Bit is equal to (k-1+k1)/k2
- Cit is a measure of catalytic efficiency
- Dit is equal to kcat
- Eit is equal to Vmax/[E]t
19Catalytic efficiency is measured as:
- AVmax/KM
- BVmax/kcat
- CKcat/Vmax
- DKcat/KM
- EKM/kcat
20The units describing "catalytic efficiency" could be:
- As-1
- BμM
- CμM/s
- D(μM-1 s-1)
- EμM-1
21Two researchers measuring the same enzyme reaction at the same substrate concentration report two different Vmax values. Which is the best possible explanation for this?
- AThe same enzyme can have different catalytic efficiencies
- BThe same enzyme can have different Km values
- CThe same enzyme can have different kcat values
- DThe reactions were carried out with different concentrations of enzyme
- EThis is not a Michaelis-Menten enzyme.
22Which of the following is true about initial velocities in Michaelis-Menten kinetics(VO)?
- AVO is the velocity of formation of the ES complex
- BVO is the velocity of product formation once ES is at a steady state concentration
- CVO is the velocity of catalysis when E=ET
- DVO = k2[ET]
- Eall of these are true
23Which of the following most accurately defines the term "initial velocity" in enzyme kinetics?
- AThe point in time right before the enzyme-substrate complex is formed
- BThe point in time when substrate has been depleted to half its original concentration
- CThe point in time that product concentration reaches half its eventual value
- DThe point in time after the enzyme-substrate complex is formed, but before much product is produced.
- EThe point in time when substrate and product concentrations are equal.
24Which of the following most accurately defines the term "steady state" in enzyme kinetics?
- AThe time right before the enzyme-substrate complex is formed.
- BThe time when substrate has been depleted to half its original concentration
- CThe time that product concentration reaches half its eventual value
- DThe time after the enzyme-substrate complex is formed, but before much product is produced.
- EThe time during which the enzyme-substrate concentration does not change
25The following graph is from an enzyme kinetics experiment collected at an enzyme concentration of 5 μM. Which value is nearest to VMax?
- A25μM
- B100 μM
- C50 μM/s
- D100 μM/s
- E1 μM-1 s -1
- F100 μM-1 s -1
26Which value is nearest to KM?
- A1 nM
- B1μM
- C25μM
- D100 μM
- E1 mM
- F100 s^-1
27For an enzyme-substrate pair with Km = 10 μM and kcat = 4 s-1, what is Vo for a reaction containing 10 nM enzyme with 10 μM substrate?
- A20 nM s-1
- B2 nM s-1
- C30 nM s-1
- D10 nM s-1
- E40 nM s-1
28The following enzyme kinetics data are for a reaction containing 2 μM enzyme
(where [S] is the substrate concentration and V0 is the initial velocity). What is Kcat for
this reaction?
- A20μM
- B110 μM/min
- C55 min-1
- D110 min-1
- E220 min -1
29KM for this reaction is approximately
- A10μM
- B20μM
- C30μM
- D102 μM/min
- E110 μM/min
30What would the initial velocity (Vo) of the reaction be at [S] = 200 μM?
- A10μM
- B30μM
- C55 μM/min
- D102 μM/min
- E110 μM/min
- F220 μM/min
31Which value is nearest to the "catalytic efficiency" of this enzyme for this reaction?
- A10 μM
- B30 μM
- C3 μM-1min-1
- D20 μM-1min-1
- E28 μM/min
- F110 μM/min
32Which of the following is true about the double reciprocal plot below?
- Athis is an example of non-competitive inhibition
- Bthis is an example of competitive inhibition
- Cthis is an example of mixed inhibition
- Dthis is an example of irreversible inhibition
- Ethe type of inhibition is not evident from these data
33When ingested, methanol is converted into toxic substances by the liver enzyme, alcohol dehydrogenase. Ethanol is sometimes used in hospital emergency rooms to treat patients who have ingested methanol. The active site of the enzyme cannot distinguish between the two compounds and will therefore bind both compounds. The principle behind this medical treatment is:
- AEthanol acts as a uncompetitive inhibitor, blocking the enzyme from converting methanol into its toxic products
- BEthanol acts as a non-competitive inhibitor, blocking the enzyme from converting methanol into its toxic products
- CEthanol acts as a competitive inhibitor, blocking the enzyme from converting
methanol into its toxic products - DEthanol acts like a hormone, regulating the activity of the enzyme
- EEthanol relieves the pain of methanol toxicity by getting the patient drunk
34Which type of reversible inhibitor binds only to the ES complex
- AUncompetitive
- BSuicide
- CNoncompetitive
- DCompetitive
35Which type of reversible enzyme inhibitor binds to both the free enzyme and the ES complex?
- ATwo of these
- BNone of these
- CUncompetitive
- DCompetitive
- ENoncompetitive
36The data on the figure below are from an enzyme kinetics experiment in the presence and absence of an inhibitor, conducted with an enzyme concentration of 3 nM. In each curve, the data approach the same maximum value velocity. Which answer is closest to the value of KI, the equilibrium constant for binding of the inhibitor?
- Athere is no way to tell from only these data
- B10 μM
- C0.1 μM
- D1 μM
- E100 μM
37Which answer is closest to the value of "catalytic efficiency" for this enzyme?
- A1,000 μM-1s-1
- B10,000 μM/s
- C1,000 μM/s
- D10,000 μM-1s-1
- E100 μM/s
- F100 μM-1s-1
38The data on the figure below are from an enzyme kinetics experiment in the presence and absence of an inhibitor, conducted with an enzyme concentration of 3 nM. In each curve, the data approach the same maximum value. Which value is closest to the KM of the enzyme in the absence of inhibitor? [blank_start]7[blank_end] μM
- A7
39Below are enzyme kinetic data from an experiment in the presence and absence of an inhibitor, conducted with an enzyme concentration of 2 nM. Which type of inhibition below best accounts for these data?
- Acompetitive
- Buncompetitive
- Cnoncompetitive
- Dirreversible
- Ecovalent
- Fyou cannot tell from only these data
40Which value is closest to the KM of the enzyme in the absence of inhibitor? [blank_start]5[blank_end] μM
- A5
41Below are the enzyme kinetic data from an experiment in the presence and absence of an inhibitor, conducted with an enzyme concentration of 2 nM. Which value is closest to the catalytic efficiency of the enzyme in the absence of inhibitor?
- A0.1 s^-1
- B5μM
- C2 μM/s
- D25 μM^-1s^-1
- E2.5 μMole^-1s^-1
- F25 s^-1
42Which value is closest to the Vmax of the enzyme in the absence of inhibitor? [blank_start]0.5[blank_end] μM/s
- A0.5
43Below are enzyme kinetic data from an experiment in the presence and absence of an inhibitor, conducted with an enzyme concentration of 2 nM. Which type of inhibition below best accounts for these data?
- Acompetitive
- Buncompetitive
- Cnoncompetitive
- Dirreversible
- Ecovalent
- Fyou cannot tell from only these data
44Which value is closest to the kcat of the enzyme in the absence of inhibitor?
- A0.1 μM
- B5 μM
- C2 μM/s
- D1,000 s-1
- E2.5 s-1
- F250 μM-1 s-1
45You are studying an enzyme with a catalytic efficiency of 6,500. A point mutation causes kcat to drop 15-fold and KM to increase 3-fold. How does the catalytic efficiency of the mutant compare to the wild-type?
- Aincrease 45-fold
- Bdecrease 5-fold
- Cdecrease 45-fold
- Dincrease 5-fold
- Eyou can't tell from this information
46You are studying an enzyme with a catalytic efficiency of 6,500. A point mutation causes this value to drop to 150. This change is due to the point mutation affecting
- AKM
- Bkcat
- CVmax
- Dyou can't tell from this information
47In a hypothetical enzyme, two histidines act as an acid and base, respectively. Mutation of each individually decreases the catalytic rate approximately 104, mutation of both together:
- Areduces the rate ~108
- Breduces the rate significantly less than 104
- Creduces the rate ~10
48Which statement distinguishes between single (SD) and double displacement (DD) bi-substrate reactions?
- AThe order in which products leave
- BThe presence of a ternary complex in DD but not in SD
- CThe presence of a ternary complex in SD but not in DD
- DNone of these
- EThe order in which substrates add
49Diisopropylfluorophosphate (nerve gas) is a ____ of acetylcholinesterase
- Aa competitive inhibitor
- Ba noncompetitive inhibitor
- Can uncompetitive inhibitor
- Da mixed inhibitor
- Ean irreversible inhibitor
- Ffan allosteric activator
50What best distinguishes an "affinity label" inhibitor from a "suicide" inhibitor?
- Aaffinity label inhibitors are competitive, but suicide inhibitors are non competitive
- Baffinity label inhibitors bind the active site and react with especially reactive
groups, suicide inhibitors bind the active site and react as a result of chemistry characteristic of the active site - Caffinity label inhibitors are irreversible, but suicide inhibitors are reversible
- Daffinity label and suicide inhibitors are the same thing
- Eaffinity label inhibitors bind the active site, but suicide inhibitors bind remotely
51How might knowledge of an enzymatic mechanism assist in drug design efforts?
- AAll of these
- BDetermining what the correct substrate is
- CHighlighting which residues to mutate to remove activity
- DNone of these
- EDetermination of the transition state for design of tight binding inhibitors
52Transition state analogs are likely to be which type of enzyme inhibitor?
- Acompetitive
- Brandom sequential
- Cnoncompetitive
- Dallosteric
- Eordered sequential
53You have synthesized two transition state analogs for a particular enzyme catalyzed reaction. One contains a positive charge at the reacting center, the other a negative charge. The one with the positive charge binds less tightly than the substrate, while that with the negative charge binds much more tightly. What do you infer regarding the true TS for the catalyzed reaction?
- Ait contains a negative charge at this position
- Bnothing can be inferred from these results
- Cit is not charged at this position
- Dit contains a positive charge at this position
54Choose the false statement
- AEnzymes can affect a million-fold or more enhancements in reaction rates
- BEnzymes are not used up during normal catalysis of reactions.
- CAll proteins are enzymes
- DEnzymes can lower the energy of the transition state of the reaction it catalyzes
- EAn enzyme must bind the reactant in some way in order to catalyze a reaction
55The one catalytic strategy that every enzyme uses is
- Ageneral acid
- Bapproximation
- Cspecific electrostatic interactions
- Dcovalent attachment
- Egeneral base
56In the active site below, His is serving what function with respect to Ser?
- AActing as an acid
- BActing as an base
- CStabilizing substrate binding
- DFacilitating product release
- EActing as both an acid and a base
57The catalytic histidine in Serine and Cysteine proteases acts
- Ato electrostatically stabilize the oxyanion
- Bto bind the catalytic metal
- Cas a general acid
- Das a general base
- Enone of these
58A serine proteases is best defined as
- AAn enzyme that hydrolyzes proteins at the carboxy side serine amino acides
- BAn enzyme that hydrolyzes proteins using an active site containing serine
- CAn enzyme that hydrolyzes proteins using an active site containing alanine
- DAn enzyme that hydrolyzes proteins at the amino side serine amino acids
- EAn enzyme that hydrolyzes proteins using an active site containing threonine
59In the serine proteases, the catalytic triad refers to
- AA three step mechanism
- BThree subunits of a protein that form an active site
- CThree residues that work together to act as a nucleophile
- DThree residues that work together to bind the substrate
60Which answer below best explains how the aspartate found in the catalytic triad of serine proteases contributes to peptide bond hydrolysis
- AIt serves as an acid
- BIt serves as a base
- CIt serves as both an acid and a base
- DIt is responsible for binding the substrate
- Eit is responsible for substrate release
61Which answer below best explains how the histidine found in the catalytic triad of serine proteases contributes to the reaction cycle?
- AIt serves as an acid
- BIt serves as a base
- CIt serves as both an acid and a base
- DIt is responsible for binding the substrate
- Eit is responsible for substrate release
62Which strategy(ies) is/are used by serine proteases in stabilizing the charges in the transition state?
- Aapproximation, general acid, covalent catalysis, electrostatic interactions
- Bapproximation, electrostatic interactions
- Cgeneral base, covalent catalysis, electrostatic interactions
- Dapproximation, general base, covalent catalysis, electrostatic interactions
- Eapproximation
63A feature common to oxyanion holes in different Ser proteases is
- ATyr side chains
- BThe presence of amide groups positioned to stabilize the negatively charged
tetrahedral intermediate. - CThe presence of amide groups positioned to stabilize the positively charged tetrahedral intermediate
- DThe presence of carbonyl groups positioned to stabilize the positively charged
tetrahedral intermediate. - EThe presence of carbonyl groups positioned to stabilize the negatively charged tetrahedral intermediate
64A common feature of oxyanion holes in serine proteases is
- Athe presence of amide groups and a negative electrostatic environment
- Bthe presence of carbxyl groups and a negative electrostatic environment
- Cthe presence of carboxyl groups and a positive electrostatic environment
- Dthere are no common features as the oxyanion hole evolved divergently
- Ethe presence of amide groups and a positive electrostatic environment
65In the serine proteases, the oxyanion hole is an example of
- Aa general base (proton acceptor)
- Ba general acid (proton donor)
- Celectrostatic stabilization
- Da site for covalent attachment
66The “P1 pocket” of serine proteases is responsible for which of the following
- AIt serves as an acid
- BIt serves as a base
- CIt serves as both an acid and a base
- DIt is responsible for binding the substrate specificity
- EIt is responsible for substrate release
67In the laboratory you discover "crypsin", a proteolytic enzyme that cleaves peptides on the carboxy side of Asp and Glu. The "P1 pocket" of crypsin would probably contain what amino acid side chain?
- AAsp and Glu
- Blue
- CPhe
- DLys or Arg
- ETyr
68Which of the following best describes a cysteine protease?
- AThe active site contains two Cys side chains that work in concert for nucleophilic attack.
- BThey use a catalytic triad of Asp-His-Cys to catalyze peptide bond hydrolys
- CThey cleave peptides on the carboxy terminal side of Cys residues
- DThey cleave peptides on the amino terminal side of Cys residues
- EThe active site uses a His side chain to activate the Cys thiol for nucleophilic
attack.
69Which of the following best describes an aspartyl protease?
- AThe active site contains two Asp side chains that work in concert for nuclophilic attack
- BThey cleave peptides on the carboxy terminal side of Asp residues
- CThey cleave peptides on the amino terminal side of Asp residues
- DThe active site uses a His side chain to activated the Asp carboxyl for nucleophilic attack
- EThey use a catalytic triad of Asp-His-Set to catalyze peptide bond hydrolys
70The "HIV protease", which is essential for HIV replication, is what kind of protease?
- AA Ser protease
- BA metalloprotease
- CA glutamyl protease
- DA Cys protease
- EAn aspartyl protease
71Which of the following best describe metaloproteases?
- AThe active site uses a Cys side chain to activate the Asp carboxyl for nucleophilic attack
- BThey cleave peptides on at sites containing metals
- CThe active site contains two Asp side chains that work in concert for nucleophilic attack
- DThey use a catalytic triad of Asp-His-Ser to catalyze peptide bond hydrolysis
- EThey use metal ions (often zinc) to active water for nucleophilic attack
72In the carbonic anhydrase reaction, what directly serves as the nucleophile?
- Acarbon dioxide
- Bhydroxide ion
- CHis
- Dzinc
- EMg
73Carbonic anhydrases provided early examples of what catalytic strategy?
- Ause of an electrostatic interaction in catalysis
- Buse of a metal ion co-factor in catalysis
- Cuse of a covalent attachment in catalysis
- Duse of a general acid/base in catalysis
74How is zinc held into the active site of carbonic anhydrase?
- Acoordination by tyrosine side chains
- Bit is held in a heme prosthetic group
- Ccoordination by histidine side chains
- Dit is not tightly held, and is free to dissociate
- Emultiple weak force interactions
75Some of the energy of binding of a restriction enzyme to its cognate (specific) DNA sequence is used to
- Adistort the DNA substrate to bring it near the magnesium sites of the enzyme
- Bovercome methylation of the DNA substrate
- Cmethylate the DNA substrate
- Dprevent distortion the DNA substrate to keep it near the magnesium sites of the enzyme
76The overall free energy of binding of a restriction enzyme to nonspecific DNA is ______ than that for binding to its cognate (specific) DNA sequence.
- Athe same
- Blessor
- Cnone of the above
- Dgreater
77The induced conformational change in restriction enzymes provides the binding site for:
- Athe hydrolytic water molecule
- Bnone of these
- Cthe magnesium co-factor
- Dthe cognate DNA substrate sequence
78The class of enzymes called myosins share which function
- Aphoto reception
- Bpeptide bond formation
- Cthe net synthesis of ATP from ADP and inorganic phosphate
- Dthe use of ATP to drive the motion of molecules within cells
- Eproteolysis
79The equilibrium constant for ATP formation from ADP + inorganic phosphate in the active site of myosin is:
- A~0.01
- B~100
- C~1
- D~ 1000
- Ethis cannot be measured
80You have an enzyme that catalyzes ATP hydrolysis. In your reactions with ATP, you add a high concentration of an irreversible inhibitor. Which of the following is true about subsequent catalysis?
- AThere will be little subsequent catalysis
- BThere will be little subsequent catalysis unless you add a lot more ATP.
- CThere will be little subsequent catalysis unless you dilute you enzyme.
- DThere will be little subsequent catalysis unless you heat your reaction
- EOnly the reverse reaction (ATP formation from ADP and Pi) will be observed.
81Both the Haber process and biological nitrogen fixation have as their endpoint which of the following major products?
- Anitrate
- BDNA
- Cdiatomic nitrogen
- Dammonia
- Eamino acids
82Which of the following best describes an “allosteric ” enzyme?
- Athe enzyme is made up of only one polypeptide subunit
- Bthe enzyme is regulated by phosphorylation
- Cthe enzyme binds only to substrate and not to any regulatory molecule
- Dbinding of a regulatory molecule to one site affects the ability of the enzyme to bind substrate at a distant catalytic site
83A positive allosteric effector would
- Ablock enzyme activity
- Breduce enzyme activity
- Cstimulate enzyme activity
- Dreduce Kcat
- Enone of the above
84A negative allosteric effector would
- ABlock the enzyme activity completely
- BReduce enzyme activity
- CStimulate enzyme activity
- DReduce kcat
- ENone of the above
85In your work with aspartate transcarbamoylase, you have a large concentration of CTP in your reaction mixture. What effect will this have on the reaction it catalyzes?
- Anothing will happen in this particular reaction
- Bthe reaction will be promoted
- Cthe reaction will be inhibited
- Dthere is not enough information provided
86ATP is most accurately characterized as what with respect to its interaction with aspartate transcarbamolyase?
- Aa homotropic activator
- Ba homotropic inhibitor
- Can allosteric activator
- Dan allosteric inhibitor
87The effect of CTP on aspartate transcarbomylase is best described as
- Aa homotropic inhibitor
- Ba homotropic activator
- Can allosteric inhibitor
- Dan allosteric activator
88ATCase is cross-linked in the T state so that it cannot shift to the R state. Which of
the following can it bind?- ACTP
- BATP
- Csubstrate (aspartate and carbomoyl phosphate)
- Dall of these
- Enone of these
89Which of the following quaternary structural organizations could NOT exhibit cooperativity?
- Atrimer
- Ball of these could exhibit cooperativity
- Cdimer
- Dtetramer
90Bisphosphoglycerate could be considered a (in terms of its allosteric regulation):
- Aa positive homotropic effector of hemoglobin
- Ba negative homotropic effector of hemoglobin
- Ca positive heterotropic effector of hemoglobin
- Da negative heterotropic effector of hemoglobin
- Enone of the above
91Oxygen could be considered a (in terms of its allosteric regulation):
- Aa positive homotropic effector of hemoglobin
- Ba negative homotropic effector of hemoglobin
- Cnone of the above
- Da negative heterotropic effector of hemoglobin
- Ea positive heterotropic effector of hemoglobin
92A positive heterotropic effector would do which of the following (in the MWC model for allostery)?
- ABind more tightly to the T state
- BBind more tightly to the R state
- CStabilize both the T and R states for maximal activity.
- DInhibit substrate binding
- ENone of the above
93You have an enzyme that is regulated by allostery. Regulator "A" binds to the T state of the protein and regulator "B" binds to the R state of the protein. If B is added to the solution, what happens in terms of the MWC model?
- ASome of the subunits in a single protein molecule will be R, others T
- BL will remain the same, the affinity of the R state will decrease
- CL will increase
- DL will remain the same, the affinity of the R state will increase
- EL will decrease
94The enzyme phosphofructokinase catalyzes an important step in glycolysis, converting fructose-6-phosphate to fructose-1,6-bisphosphate, eventually (several steps later) producing ATP from ADP. Phosphofructokinase is allosterically regulated. Which of the following is most likely to be an allosteric inhibitor of phosphofructokinase?
- AATP
- BADP
- Cfructose-6-phosphate
- Dnone of these
- Eall of these
95The enzyme phosphofructokinase catalyzes an important step in glycolysis, converting fructose-6-phosphate to fructose-1,6-bisphosphate, eventually (several steps later) producing ATP from ADP. Phosphofructokinase is allosterically regulated. Which of the following is most likely to be an allosteric activator of phosphofructokinase?
- AATP
- BADP
- Cfructose-6-phosphate
- Dnone of these
- Eall of these
96The enzyme phosphofructokinase catalyzes and important step in glycolysis, converting fructose-6-phosphate to fructose-1,6-bisphosphate, eventually (several steps later) producing ATP from ADP. Phosphofructokinase is allosterically regulated. Which of the following is most likely to be an allosteric effector of phosphofructokinase?
- AATP
- BADP
- CFructose-6-phosphate
- DFructose-1,6-bisphosphate
- EAll of these
97The enzyme fructose-1,6-bisphosphatase is allosterically activated by citrate, and allosterically inhibited by AMP. With respect to the MWC model for allosteric regulation, AMP binds more tightly to which conformation of fructose-1,6-bisphosphatase?
- AR state
- BT state
- CL state
- Dnone of these
- Eall of these
98The enzyme fructose-1,6-bisphosphatase is allosterically activated by citrate, and allosterically inhibited by AMP. With respect to the MWC model for allosteric regulation, citrate binds more tightly to which conformation of fructose-1,6-bisphosphatase?
- AR state
- BT state
- CL state
- Dnone of these
- Eall of these
99Which method of regulation provides the fastest control over enzymatic activity?
- APost-translational modification
- BAllostery
- CProteolytic degradation
- DTranscriptional
100What is the most basic, and most common means of controlling enzymatic activity?
- Areversible covalent modification
- Bproteolytic processing of a zymogen
- Callosteric regulation
- Dchanging enzyme expression level (amount present)
101Which of the following best describes the general type of enzymatic regulation distinguished as "covalent catalysis"
- Acovalent bonds in the substrate are broken when the product is formed
- Bcovalent disulfide bonds are formed or broken during the reaction
- Ccovalent bonds are broken by hydrolysis
- Das part of the reaction a covalent bond is formed between a functional group on the enzyme and the substrate
- Enew covalent bonds are formed during the reaction
102In studying a hydrolytic enzyme you observe that the stereochemistry of the product is the same as that of the substrate. What does this indicate about the enzymatic mechanism?
- AUse of approximation
- BUse of electrostatic interactions
- CUse of covalent catalysis
- DUse of a metal ion
- ENone of these
103An enzyme you are studying isolated in vitro is found to exceed catalytic perfection. How can you best explain this phenomenon?
- Aallostery increases Vmax
- Bmolecular attraction (i.e., electrostatic attraction of the substrate to the active site)
- Callostery increases KM
- Dsteric hindrance
104Which of the following amino acid side chains could be phosphorylated by a kinase?
- ALys
- BArg
- CSer
- DTrp
- Enone of the above
105The function of the "pseudo substrate" sequence found in the regulatory subunit of protein kinase A is which of the following?
- Aactivating the kinase by accepting a phosphate group from the kinase
- Binhibiting the kinase by binding the kinase active site
- Cbinding AMP to inhibit the enzyme
- Dbinding ATP to inhibit the enzyme
- Enone
106The enzyme hexokinase has a Km fro glucose that is 0.15 mM. The concentration of glucose in the cytosol might fluctuate between 1-5 mM. Evaluate the following statement as true or false: Hexokinase activity is likely to be regulated physiologically be changes in glucose concentrations.
- AVerdadeiro
- BFalso
107Hexokinase has a Km of 0.05 mM for the substrate D-glucose and a Km of 1.5 mM for the substrate D-fructose. From this we can interpret that:
- AD-fructose is a better substrate for hexokinase than D-glucose (A)
- BIt takes 1.5mM D-fructose for the reaction to reach Vmax (B)
- CHexokinase has a greater affinity for D-fructose than for D-glucose (C)
- DHexokinase has a greater affinity for D-glucose than for D-fructose (D)
- EA, B, and D above
108How is protein kinase A kept inactive in the absence of its cAMP activator?
- Aphosphorylation block of protein substrate binding
- BcAMP is a critical enzymatic co-factor
- Ccompetitive binding of a pseudosubstrate
- Dphosphorylation block of ATP binding
- EcAMP is a co-substrate
109Protein kinase A is activated by binding to which of the following molecules?
- Aphosphate
- Bphosphatase
- Ccyclic AMP (cAMP)
- DATP
- EAMP
110Specific cleavage at single peptide bond can activate enzymes?
- AVerdadeiro
- BFalso
111Which of the following is FALSE about chymotrypsin?
- AChymotrypsin is made from chymotrypsinogen.
- BFormation of chymotrypsin requires the action of a protease enzyme
- CChymotrypsin is a reversibly activated form of chymotrypsinogen.
- DMature alpha-chymotrypsin is held together by disulfide bonds
- ENone of these statements are false
112Regulation of the process of blood clotting is best described as
- Aallosteric regulation
- Ba zymogen cascade
- Creversible, with little covalent modification of enzymes
- Dirreversible, with a lot of covalent modification of enzymes
- Eboth a zymogen cascade, and irreversible, with a lot of covalent modification of enzymes
113How is blood clotting initiated by even relatively small injuries?
- Aprotein phosphorylation
- Bnone of these
- Cisozyme variation in quaternary structure
- Dprotein glycosylation
- Eproteolytic-zymogen cascades
114Which distinguishes the "intrinsic" blood clotting pathway from the "extrinsic"?
- Aone causes internal clots, the other external
- Bone is reversible, the other irreversible
- Conly one uses cross-linked fibrin to build a clot
- Done is initiated by blood contacting a damaged surface, the other by signaling molecules released from the site of damage
- Enone of these
115Why does the pancreas produce an essentially irreversible inhibitor of trypsin?
- Ato prevent premature activation of digestive enzymes
- Bto enable activation of the trypsin inhibited immune system response
- Cto prevent inappropriate activation of the blood clotting cascade
- Dto prevent premature release of active insulin
116Which of the following most specifically describes the consequences of vitamin K deficiency?
- AHydroxyl proline is not produced in collagen
- BChymotrypsin is not produced from chymotrypsinogen
- CBlood clots are not cross-linked to form “hard” clots
- DCarboxyglutamate is not formed in prothrombin
- EEnteropeptidase is not activated to start digestion
117Which of the following statements about isoenzymes is FALSE?
- AIsoenzymes catalyze the same basic reaction.
- BKcat could vary among isoenzymes
- CKM could vary among isoenzymes
- DIsoenzymes are a specific example of zymogen regulation of enzyme function
- EAll of the above are true (there is no false answer).
118Which of the following is not an example of covalent modification of proteins for regulation of their functions?
- Azymogen cascades
- Bisozyme variation in quaternary structure
- Cprotein phosphorylation
- Dprotein glycolsylation
- Enone, they are all examples
119Why would doctors test for lactate dehydrogenase (LDH) isoforms in a patients
- ABecause LDH causes high blood pressure
- BBecause LDH isoforms are specific to different tissue types
- CBecause LDH is only found in the heart
- DBecause LDH is only found in the liver
- EBecause LDH isoforms change with age
120The enzyme alcohol dehydrogenase uses a zinc ion for structural support and folding, Alcohol dehydrogenase, including its zinc, could be referred to as a
- Aholoenzyme
- Bhaptoenzyme
- Capoenzyme
- Ddenatured enzyme
- Enone of the above
121The enzyme alcohol dehydrogenase uses a zinc ion for structural support and folding. If this zinc is removed, the resulting enzyme could be referred to as a:
- Aholoenzyme
- Bhaptoenzyme
- Capoenzyme
- Dnative enzyme
- Enone of the above
122Which of the following amino acid side chains could be dephosphorylated by a phosphate?
- ALys
- BArg
- CThr
- DTrp
- ENone of the above
123The following molecule is
- AD-glucose
- BL-glucose
- CD-galactose
- DL-galactose
- ED-fructose
- FL-fructose
124Which of the following compounds is D- glyceraldehyde?
- AA
- BB
- CC
- DD
- EE
- FF
125What is the stereo chemistry of these sugars?
- AAll D
- BAll L
- CA mixture of D and L
- Dnone of these
- Eyou can't tell from only these structures
126Which of the following is an epimer of glucose?
- AA
- BB
- CC
- DD
- EE
- Fnone of these
127The following molecule is:
- Aalpha-D-glucopyranose
- Bbeta-D-glucopyranose
- Calpha-D-ribopyranose
- Dbeta-D-g ribopyranose
- Ebeta-D-fructofuranose
- Fnone of the above
128What is the following structure?
- AAlpha glucopyranose
- BBeta glucopyranose
- CAlpha glucofuranose
- DBeta glucofuranose
- EBeta fructofuranose
- FNone of the above
129The molecule shown below is:
- Abeta-D-Fructose
- Balpha -D-Fructose
- Cbeta -D-Glucose
- Dalpha -D-Ribose
- Ebeta -D-Ribose
130Pentoses and hexoses will cyclize to:
- AFuranoses and pyranoses, respectively
- BBoth will cyclize to either furanoses or pyranoses
- CPyranoses and furanoses, respectively
- DPentoses only to furanoses, hexoses to both
131What is the most plausible reason that glucose is the most commonly found sugar?
- AIt’s more easily recognized than other sugars
- BIt provides more hydrogen bonding capacity than other hexoses
- CIn one chair conformation its hydroxyl’s are all equatorial
- DIt’s anomeric carbon is more reactive than other sugars
132The type of glycoside bond in the molecule shown below is:
- AN-glycoside
- BAlpha 1-6
- CBeta 1-6
- DAlpha 1-5
- EBeta 1-5
133Which of the following best describes why the annomeric carbon is reactive?
- AThe hydroxyl attached to this carbon can point up or down
- BThis carbon has two bonds to oxygen
- CThis carbon is found at the top of the pyranose chair conformation
- DThis carbon is more easily modified
134Which of the following statements about the anomeric carbon in the ring form of a hexose sugar is FALSE?
- Athe anomeric carbon is bonded to two oxygens
- Bthe anomeric carbon is always derived from carbon #1 of the hexose
- Cthe anomeric carbon can be in the alpha or beta configuration
- Dthe anomeric carbon can be involved in glycoside bonds
- Ethe anomeric carbon is derived from the carbonyl group of the linear form
135Maltose has a glycosidic linkage also found it which polysaccharide?
- ACellulose
- BStarch
- CGlycogen
- DMutan
- EChitin
- FStarch and Glycogen
136The conversion of alpha-D-Glucopyranose to beta-D-Glucopyranose is an example of what kind of chemistry?
- Atransketolation
- Bisomerization
- Coxidation
- Dreduction
- Emutarotation
137Glycoproteins have sugars generally attached to which amino acid side chains?
- Aserine, threonine, and asparagine
- BTyrosine and asparagine
- Cnone of the above is correct
- Dserine and threonine
- Eserine, tyrosine, and asparagine
138When carbohdyrates are linked to proteins by an N-glycoside bond, the amino acid that is involved in the linkage is:
- Aserine
- Bthreonine
- Casparagine
- Dhistidine
- Elysine
139When carbohydrates are linked to proteins by an O-glycoside bond, the amino acid(s) that is involved in the linkage is:
- Aserine or threonine
- Bcysteine
- Casparagine
- Dhistidine
- Elysine
140This disaccharide sucrose is composted of
- AGlucose and fructose
- BFlucose and galactose
- CGalactose and maltose
- DAll of the above
- ENone of the above
141The disaccharide maltose is composed of
- AGlucose and fructose
- BGlucose and galactose
- CGlucose and glucose
- DFructose and fructose
- ENone of the above
142The disaccharide cellobiose is composed of:
- Aglucose and fructose
- Bglucose and galactose
- Cglucose
- Dfructose
- Enone of the above
143Cellobiose and maltose differ in what regard
- ATheir constituent simple sugars
- BThe stereochemistry of their glycosidic linkages
- CTheir degrees of polymerization
- DTheir degrees of branching
- ENone of the above
144Maltose and amylose differ in what regard
- Atheir constituent simple sugars
- Bthe stereochemistry of their glycosidic linkages
- Ctheir degress of polymerization
- Dtheir degrees of branching
- Enone of the above
145Cellobiose and cellulose differ in what regard
- Atheir constituent simple sugars
- Bthe stereochemistry of their glycosidic linkages
- Ctheir degrees of polymerization
- Dtheir degrees of branching
- Enone of the above
146Amylopectin and amylose are the principle components of
- ACellulose
- BStarch
- CInsect Cell Walls
- DGlycogen
- ENone of the Above
147The polysaccharide energy storage compound found in plants is:
- Acellulose
- Bchitin
- Chyaluronic acid
- Dglycogen
- Estarch
148The most abundant polysaccharide energy storage compound found in humans is
- Acellulose
- Bchitin
- Chyaluronic acid
- Dglycogen
- Estarch
149Amylopectin most closely resembles which polysaccharide
- Acelluose
- Bglycogen
- Cchitin
- Dpeptidoglycan
- Emutan
150Which of the following is NOT a function mediated by glycosylation of glycoproteins?
- ASorting signal
- BProtein stability
- CProtein folding
- DAll of these are functions of protein glycosylation
- ECell-cell adhesion
151The oligosaccharides in glycoproteins are
- Akey mediators of catalytic activity
- Bstatic structures that strictly serve a structural role
- Cenormous carbohydrates chains that strengthen the extracellular matrix
- Ddynamic structures that can be involved in organelle retention and targeting
152In N-linked glycosylation the resulting oligosaccharides can be best described as
- Ahaving a core structure in common
- Bbeing attached to asparagine in exposed NX(S/T) motifs
- Cbeing synthesized in the cytosol and ER, then trimmed in the ER and golgi
- Dall of the above
153Cell surface carbohydrates are involved in
- Acell-cell contact
- Ball of these
- Cbacterial contact
- Dimmune self/non-self recognition
- Evirus contact
154What type of glycoprotein glycosidic linkages occur at specific sequence motifs?
- AN-linked
- BO-linked
- CS-linked
155The “ABO” blood group antigens are best described as
- AProteins
- BLipids
- CGlycoproteins
- DStarch
- ECellobiose
156A person with type “O” blood makes which antibodies?
- AA
- BB
- CO
- DA and B
- ENone of these
157A person with type “AB” blood makes which antibodies
- AA
- BB
- CO
- DA and B
- ENone of these
Informações
- Descrição
- Quiz sobre BT2, criado por dummy dummy em 18-10-2018.
- Autor
- dummy dummy
- Idioma
- English
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