Wiley-Chs. 17-19 Flashcards

1
Q

… catalyzes a substrate-level phosphorylation reaction within the citric acid cycle

A

succinyl-CoA synthetase

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2
Q

a membrane-bound enzyme of the citric acid cycle that catalyzes an oxidation reaction is….

A

succinate dehydrogenase

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3
Q

the compound … is a structural analog and competitive inhibitor of the enzyme succinate dehydrogenase

A

malonate

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4
Q

which of the following coenzymes is required by E1 of the pyruvate dehydrogenase complex for catalytic activity? …

A

thiamine pyrophosphate

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5
Q

E2 of the pyruvate dehydrogenase complex contains a lipoyl group that is covalently attached via an amide linkage to a … residue on the enzyme

A

lysine

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6
Q

condensation of …. with oxaloacetate yield citrate

A

acetyl-CoA

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7
Q

the reaction catalyzed by pyruvate carboxylase is an example of a … reaction because it replenishes the citric acid cycle intermediates that have been siphoned off for use in other reactions

A

anaplerotic

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8
Q

the isomerization of citrate to isocitrate:

A) is one major regulatory step for the citric acid cycle because it functions as a rate limiting step

B) protects cells from the toxic effects of arsenite ion

C) converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized

D) is the rxn of the citric acid cycle that occurs spontaneously without enzymatic catalysis

A

C) converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized

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9
Q

Which of the following is(are) True concerning the metabolic rxn shown below?

Pyruvate + NAD+ + CoA-SH –> Acetyl-CoA + NADH + H+ + CO2

I. the enzyme that catalyzes this reaction contains a pyridoxal phosphate prosthetic group

II. this reaction is an oxidative decarboxylation

III. The enzyme that catalyzes this metabolic conversion is activated by high concentrations of ATP

A

II only

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10
Q

which of the following coenzymes is required by the pyruvate dehydrogenase complex for reoxidation of E3?

A

NAD+

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11
Q

which of the following enzymes of the citric acid cycle is inhibited by ATP?

A. succinyl-CoA synthetase

B. alpha-ketoglutarate dehydrogenase

C. citrate synthase

D. isocitrate dehydrogenase

A

isocitrate dehydrogenase

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12
Q

which of the following organisms does not utilize the glyxolate cycle?

A. trees
B. bacteria
C. fungi 
D. mammals 
E. all of the above utilize the glyxolate cycle when necessary
A

D. mammals

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13
Q

which of the following citric acid cycle intermediates can be converted to aspartate via transamination?

A

oxaloacetate

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14
Q

Consider the following reaction which has a delta G of about +30 kJ/mol:

malate + NAD+ –> oxaloacetate + NADH + H+
in muscle cells, the reaction proceeds as written. which of the following explains how the reaction occurs as written despite the positive value for delta G?

A. it is thermodynamically favored under standard conditions

B. In the cell, it is kinetically favored, even though it’s thermodynamically unfavorable

C. the concentration of malate must be higher than oxaloacetate for this reaction to occur in the cell

D. [H+] must be higher in muscle than under standard conditions, thus altering delta G to delta G’

E. none of the above

A

C. the concentration of malate must be higher than oxaloacetate for this rxn to occur in the cell

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15
Q

Germinating plant seeds can convert acetyl-CoA (obtained from fatty acids stored as oils) into carbohydrates, whereas animals are incapable of converting fatty acids into glucose. this difference is due to the fact that:

A. plants use the glyoxylate cycle to convert two acetyl CoA to oxaloacetate, a precursor for gluconeogenesis

B. animals have glycogen and don’t need to make glucose from fatty acids

C. animals use the citric acid cycle selectively for energy production, whereas plants primarily use glycolysis

D. plant seeds use photosynthesis to make sugar

A

A. plants use the glyoxylate cycle to convert two acetyl CoA to oxaloacetate, a precursor for gluconeogenesis

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16
Q

An individual with a shortage of B vitamins (which include thiamine and riboflavin) may feel fatigued as a result of decreased pyruvate dehydrogenase activity. which of the following would be TRUE regarding this shortage?

A. the amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased

B. a decrease in the amount of NADH would likely decrease activity of citrate synthase

C. flux through the citric acid cycle would cease until adequate pyruvate is available

D. none of the above

E. all of the above

A

A. the amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased

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17
Q

which of the following steps of the citric acid cycle conserves the energy of a high energy thioester bond?

A. the rxn catalyzed by succinate dehydrogenase

B. the rxn that produces oxaloacetate

C. the condensation rxn that produces citrate

D. the rxn catalyzed by alpha-ketoglutarate dehydrogenase

E. the conversion of citrate to isocitrate

A

D. the rxn catalyzed by alpha-ketoglutarate dehydrogenase

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18
Q

which of the following enzymatic rxns is favorable both under physiological conditions and under standard conditions?

A. the rxn catalyzed by isocitrate dehydrogenase

B. the rxn catalyzed by malate dehydrogenase

C. the rxn catalyzed by succinate dehydrogenase

D. all of the above

E. none of the above

A

A. the rxn catalyzed by isocitrate dehydrogenase

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19
Q

One turn of the citric acid cycle generates

A

1 GTP, 3 NADH, 1 FADH2

20
Q

one method used by newborn mammals to generate heat is referred to as nonshivering thermogenesis. this method utilizes a protein channel called … which is present in high levels inside the mitochondria of … tissue

A

thermogenin; brown adipose

21
Q

Which of the following statements about the mitochondrial inner membrane is TRUE?
I. the inner membrane is permeable to CO2, H2O, and small ions

II. the inner membrane contains several transport proteins and membrane bound enzymes.

III. In general, a higher inner membrane surface area correlates to a higher rate of respiration

IV. the number of cristae reflects the respiratory activity of the cell

A

II, III, IV

22
Q

Which of the following is TRUE regarding the complexes within the electron transport system?
I. Complex II contributes twice as many protons to the gradient than Complex I

II. inhibition of complex II would decrease the total number of electrons moving through the electron transport chain

III. inhibition of complex II would NOT alter the amount of free energy generated from electrons originating from NADH

IV. complex I can accept electrons with higher potential than Complex II is able to accept

A

II, III

23
Q

Which of the following correctly ranks redox centers found in Complex I from lower to higher potential? a correct answer will contain redox centers which are found in only Complex I and will also rank those redox centers in order of lower to higher reduction potential.

A. FMN, Heme b560, [2Fe-2S], CoQ

B. ubiquinone, [4Fe-4S], [2Fe-2S], FMN

C. FMN, [2Fe-2S], [4Fe-4S]

D. Heme b560, [2Fe-2S], [4Fe-4S], FAD

E. FAD, [2Fe-2S], [4Fe-4S], Heme b560

A

C. FMN, [2Fe-2S], [4Fe-4S]

24
Q

which of the prosthetic groups listed can accept/donate either one or two electrons due to the stability of the semiquinone state?

A

CoQ

25
Q

Which of the following statements is(are) TRUE about oxidative phosphorylation?

I. electron transport provides energy to pump protons into the intermembrane space

II. an electrochemical gradient is formed across the inner mitochondrial membrane

III. potassium and sodium ions form an ionic gradient across the inner mitochondrial membrane

IV. complexes I, II, III, IV actively transport protons into the intermembrane space during electron transport.

A

I, II

26
Q

Consider the following half-reactions:
= –0.315 V

NAD+ + H+ + 2 e– NADH
= 0.815 V

1/2 O2 + 2 H+ + 2 e– H2O

What is the for the following redox equation?
O2 + 2 NADH + 2 H+ 2 H2O + 2 NAD+

A

+1.130 V

27
Q

Cyanide (CN-):
I. inhibition can be restored by addition of succinate
II. inhibition can be restored by addition of cytochrome c
III. inhibits electron transport which stops consumption of oxygen
IV. blocks transfer of electrons from CoQ to Complex III

A

III only

28
Q

Rotenone and amytal:
I. inhibition can be restored by addition of succinate
II. inhibition can be restored by addition of cytochrome c
III. blocks consumption of oxygen
IV. blocks transfer of electrons from CoQ to Complex III

A

I, II, III

29
Q

Antimycin A:
I. inhibition can be restored by addition of succinate

II. inhibition can be restored by addition of cytochrome c.

III. blocks consumption of oxygen

IV. blocks transfer of electrons from CoQ to Complex III

A

II, III, IV

30
Q

Which of the following best describes the function of cytochrome c oxidase?

A. cytochrome c oxidase oxidizes four consecutive cytochrome c molecules, via one-electron transfers, while simultaneously reducing one O2 to two H2O

B. Cytochrome c oxidase oxidizes two consecutive cytochrome c molecules, via two-electron transfers, while simultaneously reducing one O2 to two H2O

C. cytochrome c oxidase oxidizes four consecutive cytochrome c molecules, via one-electron transfers, while simultaneously reducing two O2 to two H2O

D. cytochrome c oxidase oxidase two consecutive cytochrome c molecules, via two-electron transfers, while simultaneously reducing two O2 to two H2O

A

A. cytochrome c oxidase oxidizes four consecutive cytochrome c molecules, via one-electron transfers, while simultaneously reducing one O2 to two H2O

31
Q

Which statement concerning the mitochondrial F0F1 ATP synthase is FALSE?

I. The F1 subunit includes rotating sets of alpha beta dimers

II. The F0 subunit includes a ring of between 9 and 12 proton-carrying polypeptides

III. The F1 subunit undergoes a series of conformational changes throughout the course of reaction

A

I only

32
Q

In theory how many protons could be pumped under standard state conditions by Complex III per mol of CoQ oxidized, considering the following information? (NOTE: mt = mitochondria)

Rxn 1: coenzyme Q + 2H+ + 2 e- coenzyme QH2
Eo≈ 0.040 V

Rxn 2: cytochrome c (Fe3+) + e- cytochrome c (Fe2+)
Eo ≈ 0.270 V

Rxn 3: H+ (outside mt) H+ (inside mt)
∆G ≈ -20 kJ/mol

Faraday constant (F) ≈ 100 kJ/V mol
Nernst equation: ∆Gº' = -nF∆E0'

A) four or less protons

B) greater than four protons but less than/equal to six protons

C) greater than six protons but less than/equal to eight protons

D) greater than 8 protons

E) cannot be determined from the information provided

A

B) greater than four protons but less than/equal to six protons

33
Q
ATP forms (is produced): 
I. upon transition from the loose to the tight form of the alpha and beta subunit complex of ATP synthase 

II. as a result of the flux of electrons through the channel formed by Fo

III. As a result of the positive ions pumped into the matrix of the mitochondrion

A. I, II, III
B. II, III
C. I, III 
D. I only 
E. II only
A

D. I only

34
Q

In a newly discovered electron transport complex a researcher has identified the redox center Fe-S, cytochrome c, and coenzyme Q. The researcher also knows that this complex ultimately passes its electrons to oxygen. What is most likely the redox center which completes this task?

A

cytochrome c

35
Q

An assembly of antenna pigments, or light harvesting complex,

A. are often cytosolic proteins containing multiple chlorophylls

B. are nearly identical in structure from species to species

C. are likely optimized to allow efficient transfer of energy throughout pigments

D. contain an alternating structure of lipid molecules and chlorophylls allowing maximal incorporation in the membrane

E. none of the above

A

C. are likely optimized to allow efficient transfer of energy throughout pigments

36
Q

Synthesis of sucrose requires which of the following?

I. glyceraldehyde-3-phosphate and/or dihydroxyacetone phosphate

II. sucrose phosphate kinase

III. sucrose phosphate phosphatase

IV. UTP

A

I, III, IV

37
Q

beta-carotene is an example of a common …

A

accessory pigment

38
Q

… are often used to ensure complete coverage of the spectrum for photosynthesis

A

carotenoids

39
Q

… aids in light absorption for photosynthesis

A

beta-carotene

40
Q

which statement about carotenoids is false?

A. beta-carotene is an example of a common accessory pigment

B. carotenoids are often used ensure complete coverage of the spectrum

C. carotenoids are contained in the prosthetic ring structure of chlorophylls

D. beta-carotene aides in light absorption for photosynthesis

E. all of the above statements are true

A

C. carotenoids are contained in the prosthetic ring structure of chlorophylls

41
Q

… oxygenates ribulose bisphosphate to form 2-phosphoglycolate and 3-phosphoglycerate

A

RuBP carboxylates

42
Q

The … minimizes the need for photorespiration

A

C4 cycle

43
Q

… and … compete for binding the RuBP carboxylase active site

A

CO2; O2

44
Q

… is thought to function as a protective mechanism to allow dissipation of unused energy

A

photorespiration

45
Q

which of the following is(are) FALSE about photorespiration?

A. RuBP carboxylase oxygenates ribulose bisphosphate to form 2-phosphoglycolate and 3-phosphoglycerat e

B. The reaction provides an additional mechanism to generate ATP and NADPH

C. The C4 cycle minimizes the need for photorespiration

D. CO2 and O2 compete for binding the RuBP carboxylase active site

E. photorespiration is thought to function as a protective mechanism to allow dissipation of unused energy

A

B. The reaction provides an additional mechanism to generate ATP and NADPH

46
Q

Based on comparison of oxidative phosphorylation to photophosphorylation, which of the following is TRUE?

A. photophosphorylation cannot be uncoupled by an ionophore like can be done with oxidative phosphorylation

B. the formation of a proton gradient is required for adequate function of both photo- and oxidative phosphorylation

C. although sequence similarities exist between the ATP synthases from each process, little structural similarity is observed

D. photophosphorylation is not dependent on spontaneous electron flow whereas oxidative phosphorylation requires that electron flow be spontaneous

E. none of the above is true

A

B. the formation of a proton gradient is required for adequate function of both photo- and oxidative phosphorylation