Deck 14: Bioenergetics and Oxidative Metabolism

Question 1

Which of the following contains high energy bonds?

A) glucose 6-phosphate.
B) creatine phosphate.
C) acetoacetate.
D) citric acid.
E) glutamine

Answer 1

creatine phosphate.

Question 2

The iron in the cytochromes function in biological systems by

A) undergoing oxygenation and deoxygenation.
B) undergoing oxidation and reduction.
C) combining with phosphate.
D) undergoing dehydration and hydration.
E) interchanging with the iron of adrenodoxin.

Answer 2

undergoing oxidation and reduction.

Question 3

Anaplerotic reactions

A) are generally endergonic.
B) are typified by that catalyzed by pyruvate kinase.
C) are defined as reactions which produce pyruvate.
D) increase the concentrations of intermediates of the Krebs cycle.
E) are typified by those catalyzed by pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase.

Answer 3

increase the concentrations of intermediates of the Krebs cycle.

Question 4

The effect of malonate on succinate dehydrogenase is

A) noncompetitive inhibition.
B) competitive inhibition.
C) irreversible inhibition.
D) uncompetitive inhibition.
E) no inhibition; it is the product of the reaction.

Question 5

The mammalian pyruvate dehydrogenase complex

A) catalyzes the conversion of pyruvate to acetyl-CoA and carbon dioxide.
B) catalyzes the conversion of pyruvate to oxaloacetate.
C) functions as a tetramer made up of two types of subunits which are identical to those of either muscle (M) or heart (H) origin.
D) utilizes NAD as the only required coenzyme.
E) catalyzes the oxidation of lactate to pyruvate.

Question 6

The tricarboxylic acid cycle does not occur in which cells in your body?

A) skeletal muscle cells
B) liver parenchymal cells
C) adipose cells
D) renal tubular epithelium
E) erythrocytes

Question 7

M1755lAll of the following concerning the human mitochondrial genetic apparatus are true EXCEPT

A) the mitochondrial genome is a circular DNA.
B) the mitochondrial genome codes for several essential proteins for oxidative phosphorylation.
C) the mitochondrial genome exhibits maternal inheritance.
D) the mitochondrial genome uses the same genetic code as the nuclear genome.
E) a mitochondrial DNA mutation results in Leber's Hereditary Optic Neuropathy.

Question 8

In order to be considered a high energy compound, a metabolic intermediate must have a free energy of hydrolysis, (delta G0 hydrolysis), equal to, or greater than ______ kilocalories / mole.

A) + 5.3
B) - 5.3
C) + 7.3
D) - 7.3
E) + 9.3

Question 9

The enzymes of the respiratory chain are

A) in the cytosol.
B) on the outer membrane of the mitochondria.
C) on the inner membrane of the mitochondria.
D) in the mitochondrial matrix.
E) in the lysosomes.

Question 10

Which coenzyme is NOT required for the activity of the pyruvate dehydrogenase complex?

A) biotin
B) lipoic acid
C) thiamine pyrophosphate
D) coenzyme A
E) flavin adenine dinucleotide

Question 11

An allosteric activator of mitochondrial NAD-linked isocitrate dehydrogenase is

A) alpha-ketoglutarate.
B) ADP.
C) NADH.
D) acetyl-CoA.
E) glucose 6-phosphate.

Question 12

How is uncoupling produced in brown adipose tissue?

A) Action of thyroid hormone on a mitochondrial thyroid receptor
B) Activation of UCP-1 by fatty acids
C) Induction of ATPase
D) Synthesis of a small non-protein uncoupling molecule
E) Transfer of protons out of the mitochondrial matrix

Question 13

All of the following are intermediates of the Krebs cycle EXCEPT

A) cis-aconitate.
B) pyruvate.
C) fumarate.
D) succinyl-CoA.
E) malate.

Question 14

All of the following reactions are observed in the tricarboxylic acid cycle EXCEPT

A) hydration of cis-aconitate to isocitrate
B) dehydration of citric acid to form cis-aconitic acid
C) oxidative decarboxylation of alpha-ketoglutaric acid to form succinyl-CoA
D) hydration of fumaric acid to form malic acid
E) decarboxylation of citric acid to form oxalosuccinic acid

Question 15

The prosthetic group in mitochondrial cytochromes is

A) FeS
B) NAD
C) heme
D) flavin
E) ADP

Question 16

Which of the following enzymes in the tricarboxylic acid cycle requires the same set of cofactors or coenzymes as the pyruvate dehydrogenase complex?

A) alpha-ketoglutarate dehydrogenase
B) isocitrate dehydrogenase
C) succinate dehydrogenase
D) malate dehydrogenase
E) citrate synthase

Question 17

The structure of oxidized flavin differs from that of fully reduced flavin by

A) one proton.
B) one electron and one proton.
C) two electrons.
D) two protons.
E) two electrons and two protons.

Question 18

Oligomycin inhibits oxidative phosphorylation by:

A) Binding to cytochromes
B) Channeling protons
C) Binding to coenzyme Q
D) Oxidizing FAD
E) Inhibiting phosphorylation

Question 19

The free energy change for a reaction at equilibrium is

A) less than 1.
B) zero.
C) greater than 1.
D) equal to -RT 1n Keq.
E) can be utilized to do work in the cell.

Question 20

Which enzyme catalyzes substrate level phosphorylation?

A) succinyl-CoA synthase
B) citrate synthase
C) alpha-ketoglutarate dehydrogenase
D) aconitase
E) succinate dehydrogenase

Question 21

What thermodynamic parameters are compatible with the spontaneity of a chemical reaction?

A) positive standard free energy change only.
B) positive standard free energy change and high activation energy.
C) negative standard free energy change and high activation energy.
D) positive standard free energy change and low activation energy.
E) negative standard free energy change.

Question 22

What effect does the chemical uncoupler 2,4-dinitrophenol have on mitochondria?

A) inhibits electron transport and oxidative phosphorylation
B) allows electron transport to proceed without ATP synthesis
C) blocks the transfer of electrons from NADH to O2
D) stimulates ATP synthesis
E) blocks the transfer of electrons from complex I to complex II.

Question 23

All of the following statements about oxidative phosphorylation are correct EXCEPT

A) ATP synthesis is driven by a pH gradient and a membrane potential.
B) ATP synthase translocates ATP through mitochondrial membrane.
C) the respiratory chain consists of three enzyme complexes linked by two mobile electron carriers.
D) the process can be uncoupled by 2,4-dinitrophenol.

Question 24

A simple explanation of the action of an uncoupler of mitochondrial oxidative phosphorylation is that it is any agent that

A) blocks the oxidation of reduced cytochrome c by cytochrome oxidase.
B) prevents formation of ATP by interacting with and blocking proton transport through the proton translocating ATPase.
C) acts to conduct protons back into the mitochondrial matrix without accompanying formation of ATP.
D) blocks proton conductance and slows oxygen uptake rates.

Question 25

The enzyme which catalyzes the entrance of acetyl CoA into the Krebs cycle is

A) aconitase.
B) citrate synthase.
C) succinate thiokinase.
D) pyruvate dehydrogenase.
E) isocitric dehydrogenase.

Question 26

A simple explanation of the action of an uncoupler of mitochondrial oxidative phosphorylation is that it is any agent that

A) blocks the oxidation of reduced cytochrome c by cytochrome oxidase.
B) prevents formation of ATP by interacting with and blocking proton transport through the proton translocating ATPase.
C) acts to conduct protons back into the mitochondrial matrix without accompanying formation of ATP.
D) blocks proton conductance and slows oxygen uptake rates.

Question 27

Which of the following enzyme systems is most analogous to the pyruvate dehydrogenase complex?

A) oxaloacetate dehydrogenase
B) succinate dehydrogenase
C) fumarase
D) isocitrate dehydrogenase
E) alpha-ketoglutarate dehydrogenase

Question 28

Which of the following is the only mobile electron carrier in the electron transport system that is neither permanently associated nor covalently attached to a protein?

A) FMN
B) coenzyme Q
C) heme a3
D) FeS cluster
E) FAD

Question 29

Oxaloacetate moves through the mitochondrial membrane

A) after conversion to glycerol phosphate.
B) by passive diffusion.
C) after reaction with carnitine.
D) after oxidation to pyruvate.
E) after reduction to malate.

Question 30

How does the "binding-change model" for synthesis and hydrolysis of ATP in the inner mitochondrial membrane work? ?

A) "Flipping" of orientation of F1Fo-ATP synthase in the membrane
B) A one-step rotation of 180o
C) Change in the binding constant for ATP on the T subunit
D) Conformation change of the b subunit resulting in release of protons
E) Rotation of the g subunit in 120o steps

Question 31

In the "Q cycle" for electron transfer and protein pumping in Complex III of the mitochondrial electron transport chain, how many proteins are taken up from the matrix side of the inner membrane and how many are released into the inner membrane space respectively?

A) 1 and 2
B) 2 and 2
C) 2 and 4
D) 4 and 2
E) 4 and 4

Question 32

All of the following molecules, without further metabolism, can cross the inner membrane of functioning mitochondria EXCEPT

A) ATP.
B) oxygen.
C) inorganic phosphate.
D) pyruvate.
E) acetyl CoA.

Question 33

The chemiosmotic hypothesis suggests that the potential energy of the electrons moving down the mitochondrial electron transport chain from a negative to a positive oxidation potential is initially conserved in the form of a

A) proton gradient across the membrane.
B) a high energy phosphate bond.
C) a different conformational form of the electron carriers.
D) a protonated form of coenzyme Q.
E) a reduced non-heme iron protein.

Question 34

The electron transport chain of mitochondria is specifically located in the

A) outer membrane.
B) intermembrane space.
C) inner membrane.
D) matrix.
E) tonoplast.

Question 35

What is the most visible sign of reactive oxygen species damage?

A) Age spots
B) Cataracts
C) Dental caries
D) Hair loss
E) Osteoporosis

Question 36

The definition of a high energy bond is a bond

A) with a high chemical bond energy.
B) which is highly unstable.
C) which is highly exergonic.
D) with a high phosphate group transfer potential.
E) with a large negative free energy change on hydrolysis.

Question 37

Respiratory control refers to the striking dependence of respiration on the availability of

A) O2
B) Glucose
C) ADP
D) ATP
E) electrons

Question 38

Employs a flavoprotein:

A) Glucose production from glycogen
B) Lactate production from glucose
C) Malate production from succinyl CoA
D) pyruvate production from fructose
E) Succinate production from succinyl CoA

Question 39

Which of the following is a potential oxidant?

A) FAD
B) NADPH
C) NADH
D) ATP
E) Fe2+

Question 40

Certain bacterial mutant lacks the kinase catalyzing the reaction ATP + GDP <==> ADP + GTP but otherwise possesses enzymes similar to those in mammals. This mutant could still produce GTP from GDP by utilizing the enzyme

A) phosphoglycerate kinase.
B) pyruvate kinase.
C) pyruvate carboxylase.
D) creatine kinase.
E) succinate thiokinase.

Question 41

Which molecule is involved in the major step for the production of superoxide in the mitochondrial electron transport chain?

A) cytochrome c
B) cytochrome oxidase
C) NADH dehydrogenase
D) Succinate dehydrogenase
E) Ubiquinone

Question 42

Which of the statements below is correct for the reaction NADH + FMN + H+ ---> NAD+ + FMNH2

A) the reaction involves only the transfer of a hydrogen atom.
B) NAD+ is the oxidant.
C) FMNH2 is the electron acceptor.
D) FMN is the reducing agent.
E) NADH is the electron donor.

Question 43

Oxaloacetate is a substrate of which enzyme?

A) isocitrate dehydrogenase
B) succinate dehydrogenase
C) fumarase
D) citrate synthase
E) aconitase

Question 44

Substrate level phosphorylation in mitochondria

A) Consumes ATP
B) Consumes NADH
C) Is catalyzed by a flavoprotein
D) Produces coenzyme A
E) Produces fumarate

Question 45

Which reaction in the citric acid cycle requires the participation of lipoic acid and thiamine pyrophosphate?

A) acetyl CoA + oxaloacetate ----> citrate
B) citrate ----> isocitrate
C) isocitrate ----> alpha-ketoglutarate
D) alpha-ketoglutarate ----> succinyl CoA
E) succinyl CoA ----> succinate

Question 46

The formation of GTP in the citric acid cycle is an example of

A) phosphorolysis.
B) oxidation.
C) oxidative phosphorylation.
D) reduction.
E) substrate level phosphorylation.

Question 47

Each of the following statements concerning mitochondrial protein synthesis are true EXCEPT which one?

A) Mitochondrial protein synthesis is inhibited by chloramphenicol.
B) The enzymes of the respiratory chain are all coded by mitochondrial genes.
C) Mitochondrial protein synthesis is initiated by N-formylmet-tRNA fmet.
D) The mitochondrial genome codes for only certain proteins of the inner mitochondrial membrane.
E) Protein synthesis in mitochondria is closely integrated with cytoplasmic protein synthesis.

Question 48

The activity of pyruvate dehydrogenase (PDH) decreases

A) as the concentration of acetyl CoA decreases.
B) as the concentration of NAD increases.
C) when the dephospho-enzyme is converted to its phospho form.
D) as the concentration of pyruvate increases.
E) as the concentration of AMP increases.

Question 49

Cyanide is toxic because it inhibits

A) succinate dehydrogenase.
B) NADH-dehydrogenase.
C) phosphorylase.
D) pyruvate dehydrogenase.
E) cytochrome oxidase.

Question 50

How does lack of oxygen in the cell decrease TCA cycle activity?

A) synthesis of lactic acid from pyruvate is inhibited
B) increased malonyl CoA inhibits carnitine acyl transferase I.
C) electron transport cannot be used to regenerate NAD+
D) epinephrine levels are increased
E) glycogenolysis is decreased, causing less requirement for the TCA cycle.

Question 51

In liver cells, substrate-level phosphorylation may be differentiated from mitochondrial oxidative phosphorylation in that all substrate-level phosphorylation

A) can continue in the presence of dinitrophenol.
B) requires inorganic phosphate.
C) forms GTP as the immediate product.
D) requires a proton gradient.
E) is characterized by all of the above.

Question 52

A substrate with a P:O ratio of 1.5 is:

A) Alpha-ketoglutarate
B) Isocitrate
C) Malate
D) pyruvate
E) Succinate

Question 53

Which is a flavoprotein?

A) isocitrate dehydrogenase
B) succinate dehydrogenase
C) carbonic anhydrase
D) citrate synthase
E) aconitase

Question 54

The uncoupling of oxidative phosphorylation in the human might be of physiological importance because it

A) allows storage of nutrients.
B) produces water.
C) increases carbon dioxide level in the blood.
D) produces heat.
E) raises the oxygen level in the blood.

Question 55

How many molecules of NAD are reduced as one molecule of pyruvate is metabolized through one turn of the Krebs cycle?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 56

A reaction between hydrogen peroxide and superoxide can produce hydroxyl radicals. What else can cause hydrogen peroxide to form this toxic species?

A) Fe2+
B) K+
C) Mg2+
D) Mn2+
E) Na+

Question 57

The ratio of NADH/NAD is greatest in

A) microsomes.
B) mitochondria.
C) nucleus.
D) cytosol.

Question 58

A major control point of the Krebs cycle is exerted at the level of

A) succinate dehydrogenase.
B) citrate synthase.
C) succinyl CoA synthase.
D) malate dehydrogenase.
E) aconitase.

Question 59

Which statement about the pyruvate dehydrogenase complex is true?

A) Lipoamide functions in the decarboxylation of pyruvate.
B) Coenzyme A is covalently bound to a lysine residue in one of the proteins of the complex.
C) phosphorylation catalyzed by a kinase results in decreased activity.
D) NADH is an allosteric activator of pyruvate oxidation.
E) The function of FAD is to oxidize NADH.

Question 60

Which enzyme occurs in mammals in both NAD- and NADP-linked forms?

A) isocitrate dehydrogenase
B) succinate dehydrogenase
C) alpha-ketoglutarate dehydrogenase
D) citrate synthase
E) aconitase

Question 61

The steady-state activity of pyruvate dehydrogenase (PDH) is reduced by increases in all of the following EXCEPT

A) acetyl CoA.
B) NADH.
C) cyclic AMP.
D) ingestion of ethanol.
E) ATP.

Question 62

Which of the following would NOT have an inhibitory effect on the flow of metabolites through the citric acid cycle?

A) High levels of ATP relative to ADP
B) Depletion of NADH by its conversion to NAD+
C) Limited availability of oxaloacetate
D) High levels of citrate
E) Depletion of acetyl-CoA

Question 63

Which is a tricarboxylic acid?

A) oxaloacetate
B) succinate
C) alpha-ketoglutarate
D) citrate
E) acetate

Question 64

What is the most reactive form of oxygen?

A) H2O
B) H2O2
C) O2
D) O2.-
E) OH.

Question 65

Oxidation of one molecule of pyruvate by the combined action of the pyruvate dehydrogenase complex and the enzymes of the citric acid cycle is thought to result in the generation of how many pairs of electrons which can move through the electron transport chain?

A) 3
B) 4
C) 5
D) 6
E) 7

Question 66

An enzyme which catalyzes the conversion of hydrogen peroxide to water and oxygen is

A) catalase.
B) invertase.
C) peroxide mutase.
D) a cytochrome.
E) glutathione peroxidase.

Question 67

Which is the immediate product of an anaplerotic reaction related to the Krebs cycle?

A) citrate
B) malate
C) oxaloacetate
D) acetyl CoA
E) pyruvate

Question 68

All of the following are found in, or associated with the mitochondrial electron transport chain EXCEPT

A) cytochromes.
B) coenzyme Q (ubiquinone).
C) proteins containing non_heme iron and sulfur.
D) proteins containing FMN.
E) substrate level phosphorylation.

Question 69

A radical is a molecule with a highly reactive unpaired electron in the outer shell. What does it need to attain its preferred state?

A) A pair of electrons
B) A proton
C) Another electron
D) Loss of a protein
E) Loss of the single electron

Question 70

All of the following statements about cytochrome c are correct EXCEPT which one?

A) The reduced form of the protein participates in electron transport by directly donating electrons to oxygen.
B) Unlike the other mitochondrial cytochromes, it is water soluble.
C) It contains iron which undergoes reversible oxidation and reduction during electron transport.
D) It is visibly colored.
E) It is reduced by the reduced form of the cytochrome bc1 complex.

Question 71

How many moles of ATP can be formed from ADP during the complete oxidation of one mole of pyruvate to carbon dioxide and water in normal liver cells?

A) 3
B) 9
C) 12
D) 15
E) 36

Question 72

All of the following items are requirements of the chemiosmotic mechanism of oxidative phosphorylation EXCEPT

A) a topologically closed, proton impermeable membrane.
B) an ATPase which can be driven in reverse by a proton gradient across the membrane.
C) a proton translocating system oriented asymmetrically across the membrane.
D) a direct coupling of electron transport to phosphorylation.

Question 73

In tightly coupled mitochondria, the rate of oxidative phosphorylation is governed by the concentration of

A) Acetyl-CoA
B) Pi
C) ADP
D) ATP
E) NADPH

Question 74

Which of the following would NOT be considered a high energy compound?

A) ATP
B) phosphoenolpyruvate
C) ADP
D) 1,3-bisphosphoglycerate
E) glyceraldehyde 3-phosphate

Question 75

Electrons from NADH produced in the cytosol by glycolysis may be transported into the mitochondrion and to the electron transport chain through which of the following compounds?

A) glutamate
B) lactate
C) malate
D) oxaloacetate
E) pyruvate

Question 76

All enzymes of the Krebs cycle, except for succinate dehydrogenase, are found in the

A) mitochondrial matrix.
B) inner mitochondrial membrane.
C) intermembrane space.
D) outer mitochondrial membrane.
E) cytosol.

Question 77

In ATP, the linkage between each of the phosphate groups is a

A) phosphomonoester.
B) phosphodiester.
C) phosphoamide.
D) phosphoanhydride.
E) phosphoenol.

Question 78

Oligomycin has a direct inhibitory effect on

A) the adenine nucleotide exchange protein.
B) ATP synthase.
C) site I of the respiratory chain.
D) site II of the respiratory chain.
E) site III of the respiratory chain.

Question 79

A typical enzyme-catalyzed reduction reaction occurring in a biosynthetic pathway would require the cofactor

A) NAD+
B) FADH2
C) FAD
D) NADPH
E) NADP+

Question 80

Succinate dehydrogenase is found in which subcellular fraction of the liver?

A) microsomes
B) mitochondrial matrix
C) Golgi apparatus
D) inner membrane of the mitochondrion
E) cytosol