Deck 3: Bioenergetics and Metabolism

Question 1

If the equilibrium constant for the reaction A $\leftrightarrow$ B is 0.5, and the initial concentration of A is 30 mM and of B is 15 mM, then the reaction

A) will proceed in the direction it is written, producing a net increase in the concentration of B.
B) will produce energy, which can be used to drive ATP synthesis.
C) will proceed in the reverse direction, producing a net increase in the concentration of A.
D) is at equilibrium.

Answer 1

is at equilibrium.

Question 2

The free-energy change of a reaction is determined by the

A) intrinsic properties of reactants and products.
B) concentrations of reactants and products.
C) temperature of reactants and products.
D) All of the above

Answer 2

D

Question 3

The $\Delta$ G°' for hydrolysis of ATP to ADP and P_i is _______ kcal/mole.

A) +14
B) +7.3
C) -7.3
D) -0.5

Answer 3

-7.3

Question 4

The hydrolysis of ATP to ADP and phosphate allows glucose-6-phosphate to be synthesized from glucose and phosphate because the

A) heat produced from ATP hydrolysis drives glucose-6-phosphate synthesis.
B) enzymatic coupling of these two reactions allows the energy of ATP hydrolysis to drive the synthesis of glucose-6-phosphate.
C) energy of glucose phosphorylation drives ATP splitting.
D) All of the above

Question 5

Under aerobic conditions, the end product of glycolysis is

A) ethanol.
B) lactate.
C) phosphoenolpyruvate.
D) pyruvate.

Question 6

Glycolysis produces four molecules of ATP from each molecule of fructose-1,6-bisphosphate because

A) two molecules of ATP are required to convert glucose to fructose-1,6-bisphosphate.
B) fructose-1,6-bisphosphate is converted into two molecules of 1,3-bisphosphoglycerate, each of which produces two ATPs when metabolized to pyruvate.
C) fructose-1,6-bisphosphate is converted into four molecules of 1,3-bisphosphoglycerate, each of which produces one ATP when metabolized to pyruvate.
D) Both a and b

Question 7

In glycolysis, the key control enzyme that is inhibited by excess ATP is

A) hexokinase.
B) phosphofructokinase.
C) alcohol dehydrogenase.
D) fructose-1,6-bisphosphate.

Question 8

Under anaerobic conditions, NADH produced by glycolysis is recycled by a reaction that produces NAD⁺ and

A) ethanol.
B) lactate.
C) pyruvate.
D) ethanol or lactate.

Question 9

Which of the following is a product of glycolysis that is transported into the mitochondria?

A) Acetate as acetyl CoA
B) Pyruvate
C) Ethanol
D) Lactic acid

Question 10

In eukaryotic cells, the citric acid cycle occurs in the

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

Question 11

The citric acid cycle consists of the oxidation of _______ to produce _______.

A) pyruvate; CO₂, NADH, and FADH₂
B) acetyl CoA; CO₂, NADH, and FADH₂
C) pyruvate; CO₂
D) acetate; CO₂

Question 12

Through the oxidation process, fatty acids produce approximately _______ energy per gram compared to carbohydrates.

A) the same
B) 50% more
C) 2.5 times more
D) 5 times more

Question 13

Fatty acids are broken down in a stepwise process, _______ carbon(s) at a time.

A) one
B) two
C) four
D) six

Question 14

Protons are freely permeable across

A) both mitochondrial membranes.
B) the inner, but not the outer, mitochondrial membrane.
C) the outer, but not the inner, mitochondrial membrane.
D) neither mitochondrial membrane.

Question 15

The inner mitochondrial membrane contains proteins that

A) synthesize ATP.
B) pump protons.
C) transport pyruvate and fatty acids.
D) All of the above

Question 16

The $\Delta$ G°' for the transfer of two electrons from NADH to O₂ through the electron transport chain is _______ kcal/mol.

A) +52.5
B) -52.5
C) +7.5
D) -7.5

Question 17

When electrons from the cofactors reduced by breakdown of one glucose are transferred to oxygen in mitochondria, the process is coupled to the formation of _______ molecules of ATP.

A) 2
B) 10-12
C) 22-24
D) 32-34

Question 18

Electron transport and oxidative phosphorylation are performed by protein complexes in the mitochondrial

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

Question 19

Coenzyme Q carries electrons from complex _______ to complex _______.

A) I; II
B) II; III
C) I; III
D) III; IV

Question 20

Peter Mitchell received the Nobel Prize in 1978 for his revolutionary hypothesis of oxidative phosphorylation, which is called the _______ hypothesis.

A) electron transport
B) substrate-level phosphorylation
C) endosymbiotic
D) chemiosmotic

Question 21

Photosynthesis uses light energy to chemically convert

A) CO and H₂O into CH₄ and O₂.
B) CH₃OH into C₆H₁₂O₆.
C) C₆H₁₂O₆ and O₂ into CO₂ and H₂O.
D) CO₂ and H₂O into C₆H₁₂O₆ and O₂.

Question 22

Photosynthesis takes place in two stages, referred to as

A) light reactions and dark reactions.
B) oxygen requiring and oxygen releasing reactions.
C) H₂O splitting and sugar synthesizing reactions.
D) chlorophyll dependent and independent reactions.

Question 23

In the light reactions of photosynthesis,

A) sugars are synthesized from CO₂ and water.
B) H₂O is converted to O₂ and NADP⁺ is reduced to NADPH.
C) oxidative phosphorylation produces ATP.
D) All of the above

Question 24

Light-dependent generation of ATP in photosynthesis occurs in the

A) stroma.
B) inner membrane.
C) thylakoid membrane.
D) thylakoid lumen.

Question 25

The electron carrier that transports electrons from cytochrome bf to photosystem I where NADP⁺ is reduced to NADPH is

A) Cytochrome c.
B) plastocyanin.
C) plastoquinone.
D) Q_A.

Question 26

ATP is synthesized in photosynthesis by which of the following means?

A) Light energy stored by chlorophyll of photosystem I is directly transferred to ATP synthase, which uses the energy to synthesize ATP.
B) Light energy absorbed by photosystems I and II generate energetic electrons that cause the cytochrome bf complex to pump protons across the thylakoid membrane; these protons drive ATP synthase to synthesize ATP.
C) Light energy absorbed by photosystems I and II generate energetic electrons that cause the cytochrome bf complex to pump protons across the inner chloroplast membrane; these protons drive ATP synthase to synthesize ATP.
D) Light energy is used to synthesize glucose, which is then metabolized to produce ATP.

Question 27

The dark reactions occur in the

A) outer membrane.
B) inner membrane.
C) thylakoid membrane.
D) stroma.

Question 28

The Calvin cycle can occur

A) in the absence of CO₂.
B) only in the presence of light.
C) in the absence of light.
D) only in the absence of oxygen.

Question 29

In the synthesis of glycogen, glucose-1-phosphate reacts with a nucleotide triphosphate to form _______-glucose.

A) ADP
B) GDP
C) CDP
D) UDP

Question 30

Gluconeogenesis can produce glucose beginning with

A) lactate.
B) pyruvate.
C) fatty acids.
D) All of the above

Question 31

The production of one glucose from two pyruvates requires _______ more than is obtained through glycolysis.

A) 2 NADH
B) 2 ATP and 2 GTP
C) 2 NADH and 2 ATP
D) 4 ATP

Question 32

The most energetically favorable reactions in glycolysis are catalyzed in reverse in gluconeogenesis by

A) shifting their equilibrium.
B) the glycolytic enzymes using ATP.
C) the use of different enzymes coupled with energy from ATP or NADH.
D) accumulation of high substrate concentrations.

Question 33

The fixation of atmospheric nitrogen can be carried out by

A) a few species of bacteria.
B) bacteria, fungi, and plants.
C) plants.
D) all eukaryotes.

Question 34

For humans, _______ essential amino acids must be provided by the diet.

A) 2
B) 4
C) 9
D) 18

Question 35

The incorporation of each amino acid into a protein is coupled to the hydrolysis of _______ molecule(s).

A) one ATP
B) two ATP
C) one ATP and one GTP
D) one ATP and two GTP

Question 36

6-Mercaptopurine is a potent inhibitor of

A) protein translation.
B) DNA synthesis.
C) conversion of pyruvate to oxaloacetate in gluconeogenesis.
D) glycogen biosynthesis.

Question 37

A nucleotide is a

A) base found in nucleic acids.
B) purine or pyrimidine base plus a five-carbon sugar.
C) purine or pyrimidine base, a five-carbon sugar, and one or more phosphate groups.
D) purine or pyrimidine base, a five-carbon sugar, and three phosphate groups.

Question 38

In anaerobic cells, the oxidation of glucose yields _______ molecules of ATP per molecule of glucose.

Question 39

Under anaerobic conditions, pyruvate can be converted to either lactic acid or _______.

Question 40

The citric acid cycle involves the addition of two carbons from the compound _______ to the four-carbon oxaloacetate to produce the six-carbon compound _______.

Question 41

The acceptor of acyl groups from pyruvate is _______.

Question 42

In addition to the three molecules of NADH produced per molecule of acetate introduced into the citric acid cycle, one molecule of an additional reduced cofactor called _______ is produced.

Question 43

The citric acid cycle produces two reduced cofactors, NADH and _______.

Question 44

During oxidation of a fatty acid, the fatty acid is joined to the molecule _______ and is broken down by stepwise removal of _______-carbon units as part of the molecule _______, which can then enter the citric acid cycle to be metabolized.

Question 45

In aerobic cells, the complete oxidation of glucose via glycolysis and the citric acid cycle yields between _______ and _______ molecules of ATP per molecule of glucose, depending on how the electrons from NADH enter the mitochondria.

Question 46

ATP is produced in mitochondria by a process called _______.

Question 47

The reduced cofactors NADH and FADH₂ transfer their electrons to O₂ to produce H₂O via a set of four membrane-bound complexes collectively called the _______. These complexes pump _______ across the _______ membrane.

Question 48

The mobile carrier that transfers electrons from Complex I or II to Complex III of the electron transport chain is called _______.

Question 49

The ultimate acceptor of electrons from the electron transport chain is _______.

Question 50

The only complex in the mitochondrial electron transport chain that is not involved directly in the transport of protons is complex _______.

Question 51

The _______ produced by the electron transport chain drives a flow of these ions through a complex of proteins called _______ to produce ATP from ADP and P_i.

Question 52

The light reactions in photosynthesis produce _______ and _______ while the dark reactions produce _______.

Question 53

In chloroplasts, the proton gradient that drives ATP production is established across the _______ membrane.

Question 54

In photosystem II, water is split to produce _______ and _______, while in photosystem I the movement of electrons is coupled to the reduction of _______.

Question 55

Photosystem II is also involved in cyclic electron flow in which electrons are transferred to _______. This electron transfer is coupled to the generation of a _______ gradient and ultimately to the generation of _______.

Question 56

The ATP and NADPH produced by photosynthesis are used to synthesize _______ from _______ and _______.

Question 57

In the dark reactions, _______ is synthesized in the chloroplast stroma by the _______ cycle.

Question 58

Plants store glucose in the form of _______, and animals store glucose in the form of _______.

Question 59

_______ differs from a reverse of glycolysis in that energetically unfavorable reverse steps of glycolysis are replaced with energetically favorable reactions catalyzed by different enzymes.

Question 60

Amino acids are synthesized from intermediates in _______ and from the _______.

Question 61

In the process of protein synthesis, _______ serves as a template for translation.

Question 62

The reduction of atmospheric N₂ to NH₃ by certain species of bacteria is referred to as _______.

Question 63

Polymerization of DNA and RNA is driven by _______ as activated precursors.

Question 64

The compound 6-mercaptopurine has been used successfully to treat _______.

Question 65

ATP serves to transfer energy from energy-producing to energy-requiring reactions.

Question 66

Glycolysis can act on glucose or fatty acids as initial substrates.

Question 67

Per unit weight, carbohydrates are more efficient energy storage molecules than lipids.

Question 68

Most of the ATP derived from the breakdown of glucose in aerobic cells is derived from glycolysis.

Question 69

Most of the ATP derived from the breakdown of glucose in anaerobic cells is derived from glycolysis.

Question 70

The oxidation of NADH via the electron transport chain is a highly efficient process with little or no energy loss to heat.

Question 71

The electron transport chain consists of four complexes, I through IV.

Question 72

The final electron acceptor in oxidative phosphorylation is O₂.

Question 73

The potential energy stored in the proton gradient that drives oxidative phosphorylation is totally chemical in nature.

Question 74

The mode of action of mitochondrial ATP synthase involves mechanical coupling between protein subunits and hence can be considered an example of a rotary motor.

Question 75

In photosynthesis, energy from sunlight is used to drive the synthesis of ATP and NADPH.

Question 76

Photosystems I and II share the property of absorbing light and transferring energy to chlorophyll.

Question 77

Plastoquinone (PQ) can carry electrons from both photosystems I and II to cytochrome bf.

Question 78

Photosystems I and II both contribute electrons to cytochrome bf to generate a proton gradient that powers ATP generation by the chloroplast ATP synthase.

Question 79

The dark reactions of photosynthesis are directly coupled to chlorophyll and light energy.

Question 80

The Calvin cycle in plants, in which glucose is synthesized from CO₂, is an example of a light reaction.