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XX. BioChemistry > Exam 4 > Flashcards

Exam 4 Flashcards

1
Q

Which of the following is incorrect about oxidative phosphorylation?
A. The reduced cofactors NAD+ and Q are re-oxidized by releasing their electrons
B. The free energy released in the process is conserved in a manner that powers ATP synthesis
C. The process is highly exergonic
D. Released electrons flow through a series
of electron carriers

A

A. The reduced cofactors NAD+ and Q are re-oxidized by releasing their electrons

NOT REDUCED

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2
Q

The reduction potential (E) indicates a substance’s ability to:
A. Accept electrons
B. Donate electrons
C. Be oxidized
D. Release its electrons
E. None of the other choices

A

A. Accept electrons

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3
Q

Which of the following has the highest affinity for electrons? The reduction potential (E) values are between parentheses.
A. Acetate (-0.581 V)
B. FAD (~0 V)
C. Oxygen (0.815 V)
D. Ubiquinone (0.045 V)
E. Lipoic acid (-0.29 V)

A

C. Oxygen (0.815 V)

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4
Q

If F is the Faraday constant and ∆E is the reduction potential change, the free energy change is equal to:
A. The (# of e-)x(F)x(∆E)
B. The (-) of (# of e-)x(F)x(∆E)
C. The (-) of (# of e-)x(F)/(∆E)
D. The (F)x(∆E)/(# of e-)
E. None of the other choices

A

B. The (-) of (# of e-)x(F)x(∆E)

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5
Q

Which of the following is incorrect?
A. Electron transport takes place in the mitochondria
B. The ATP translocase system exports ATP from the mitochondrial matrix
C. The ATP translocase system imports ADP to the mitochondrial matrix
D. A shuttle system moves NAD+ (formed in glycolysis) from the cytosol to the mitochondrial matrix

A

D. A shuttle system moves NAD+ (formed in glycolysis) from the cytosol to the mitochondrial matrix

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6
Q

Which of the following is incorrect about Complex I?
A. The donor of electrons is NADH
B. The acceptor of electrons is QH2
C. It contains FMN (flavin mononucleotide)
and Fe-S clusters
D. It translocates H+ from the mitochondria
matrix to the intermembrane space

A

B. The acceptor of electrons is QH2

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7
Q

Which of the following is incorrect?
A. TheFe-S clusters are prosthetic groups that transfer one electron
B. In the Fe-S clusters, Fe2+ accepts an electron becoming reduced to Fe3+
C. FMN (flavin mononucleotide) is a prosthetic group that transfers 2 electrons
D. FMN (flavin mononucleotide) accepts 2 electrons, becoming reduced to FMNH2
E. In Fe-S clusters, Fe3+ accepts an electron becoming reduced to Fe2+

A

B. In the Fe-S clusters, Fe2+ accepts an electron becoming reduced to Fe3+

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8
Q

Which of the following is incorrect?
A. Complex II of the electron transport chain is the enzyme succinate dehydrogenase of the citric acid cycle
B. Complex III contains cytochrome proteins
C. Complex III contains Fe-S clusters
D. Cytochrome proteins have heme groups
E. Heme groups of cytochrome proteins have an iron atom that can accept two electrons

A

E. Heme groups of cytochrome proteins have an iron atom that can accept two electrons

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9
Q

Which of the following is incorrect about the Q cycle?
A. Electrons are donated by QH2
B. Translocation of H+ occurs from the intermembrane space to the mitochondrial matrix
C. Electrons are transferred by cytochrome proteins and Fe-S clusters
D. Cytochrome c is the electron acceptor

A

B. Translocation of H+ occurs from the intermembrane space to the
mitochondrial matrix

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10
Q

Which of the following is incorrect about Complex IV?
A. Cytochrome c is the electron donor
B. Electrons are accepted by oxygen
C. Oxygen is oxidized to water
D. It translocates H+ from the matrix to the
intermembrane space
E. None; all the other choices are correct

A

C. Oxygen is oxidized to water

OXYGEN IS REDUCED TO WATER

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11
Q

Which of the following is incorrect about the chemiosmotic theory?
A. It connects the transport of electrons with the hydrolysis of ATP
B. Some of the complexes generate a H+ gradient across the inner mitochondrial membrane
C. Imbalance of H+ represents a source of free energy called the proton-motive force
D. Proton-motive force drives the activity of the enzyme ATP synthase

A

A. It connects the transport of electrons with the hydrolysis of ATP

SYNTHESIS OF ATP

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12
Q

Which of the following is incorrect about ATP synthase?
A. F0 is the catalytic component
B. The F0 and F1 components are
connected through the gamma subunit
C. F0 acts as a H+ channel
D. F0 is the membrane-bound component E. It is a multimeric enzyme

A

A. F0 is the catalytic component

F1 IS THE CATALYTIC COMPONENT

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13
Q

Which of the following is incorrect about the ATP synthase mechanism?
A. It is called the binding change mechanism
B. It explains how ATP is synthesized
C. It involves rotation-driven conformational changes that alter the affinity of each
catalytic subunit
D. At any moment, each catalytic site has a different conformation and binding affinity
E. None; all the other choices are correct

A

E. None; all the other choices are correct

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14
Q

Which of the following lipoproteins has the lowest amount of protein and highest amount of lipids?
A. Chylomicrons
B. VLDL
C. LDL
D. HDL
E. IDL

A

A. Chylomicrons

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15
Q

The lipoproteins that carry lipids from the small intestine to the liver and other tissues are the:
A. Chylomicrons
B. VLDL
C. LDL
D. HDL
E. IDL

A

A. Chylomicrons

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16
Q

Which of the following is incorrect?
A. Degradation of fatty acids occurs in the mitochondrial matrix
B. Degradation of fatty acids is energetically unfavorable
C. Synthesis of fatty acids occurs in the cytosol
D. Degradation of fatty acids is referred to as β oxidation
E. None; all the other choices are correct

A

B. Degradation of fatty acids is energetically unfavorable

FAVORABLE -> CATABOLISM -> OXIDATIVE -> RELEASES ELECTRONS -> CREATES ENERGY

17
Q

Which of the following is incorrect about the activation of fatty acids?
A. It occurs in the cytosol
B. They are reacted with coenzyme A to
form an acyl-CoA (fatty acyl-CoA)
C. ATP is consumed
D. None; all the other choices are correct

A

D. None; all the other choices are correct

18
Q

Which of the following is used to tag fatty acids for their translocation across the inner mitochondrial membrane?
A. Coenzyme A
B. Carnitine
C. ATP
D. UTP
E. Acyl carrier protein (ACP)

A

B. Carnitine

19
Q

What type of reaction is the 1st step (formation of a double bond from a single bond) of fatty acids degradation?
A. Reduction
B. Oxidation
C. Hydrolysis
D. Hydration
E. Hydrogenation

A

B. Oxidation

20
Q

What type of reaction is the 2nd step (addition of water across a double bond) of fatty acids degradation?
A. Reduction
B. Oxidation
C. Hydrolysis
D. Hydration
E. Hydrogenation

A

D. Hydration

21
Q

The role of NAD+ in the degradation of fatty acids is to:
A. Donate electrons
B. Accept electrons
C. Activate the fatty acids
D. Reduce the fatty acids
E. None of the other choices

A

B. Accept electrons

22
Q

Which of the following is incorrect about the conversion of acetyl-CoA (2 C) to malonyl-CoA (3 C)?
A. It is irreversible
B. It is not regulated
C. It is a carboxylation
D. It is the 1st step of fatty acid synthesis E. None; all the other choices are correct

A

B. It is not regulated

23
Q

Which of the following is incorrect about fatty acid synthesis?
A. NADH is the reducing agent
B. The growing chain of the fatty acid is attached to the acyl carrier protein (ACP)
C. It occurs in the cytosol
D. It is energetically unfavorable
E. The growing chain of the fatty acid is not attached to coenzyme A

A

A. NADH is the reducing agent

NADPH

24
Q

The multifunctional enzyme that catalyzes most of the steps of the synthesis of fatty acids is:
A. Fatty acid synthase
B. Acetyl-CoA carboxylase
C. Malonyl synthase
D. Acyl synthetase
E. Fatty acid synthetase

A

A. Fatty acid synthase

25
Q

Which of the following is incorrect about acetyl-CoA carboxylase?
A. It is the regulatory enzyme of fatty acids synthesis
B. It is inhibited by fatty acids (i.e. product inhibition)
C. It is activated by citrate
D. It catalyzes a reversible reaction
E. None; all the other choices are correct

A

D. It catalyzes a reversible reaction

26
Q

Which of the following is incorrect about the synthesis of the so-called ketone bodies?
A. They are made from acetyl-CoA
B. The process is called ketogenesis
C. The process is not regulated
D. It does not occur in the liver
E. None; all the other choices are correct

A

D. It does not occur in the liver

27
Q

Which of the following is the precursor of glycerophospholipids?
A. Acetyl-CoA
B. Phosphatidate
C. Cholesterol
D. Malonyl-CoA
E. None of the other choices

A

B. Phosphatidate

28
Q

Which of the following is incorrect about the synthesis of cholesterol?
A. It is a pathway of over 30 steps
B. It starts with acetyl-CoA
C. It is regulated
D. It occurs in the mitochondrial matrix
E. None; all the other choices are correct

A

D. It occurs in the mitochondrial matrix

CYSTOSOL IS THE SITE FOR BIOSYNTHESIS

29
Q

The regulatory enzyme of cholesterol synthesis is:
A. Acetyl-CoA carboxylase
B. HMG-CoA reductase
C. Cholesterol synthase
D. Cholesterol synthetase

A

B. HMG-CoA reductase

30
Q

Which of the following is incorrect?
A. The regulatory enzyme of cholesterol synthesis is activated by drugs called statins
B. Synthesized cholesterol can be incorporated into the cell membrane to reduce its fluidity
C. Synthesized cholesterol can have attached a fatty acid to form a cholesteryl ester
D. Cholesterol can be used to make steroid hormones and bile acids
E. None; all the other choices are correct

A

A. The regulatory enzyme of cholesterol synthesis is activated by drugs called statins

XX. BioChemistry (15 decks)

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