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XX. BioChemistry > Exam 3 Multiple Choice > Flashcards

Exam 3 Multiple Choice Flashcards

1
Q

The entire set of chemical reactions occurring in a living system is referred to as:
A. Anabolism
B. Catabolism
C. Metabolism
D. Digestion
E. Coupled process

A

C. Metabolism

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2
Q

The oxidative process of breaking down large molecules is referred to as:
A. Anabolism
B. Catabolism
C. Metabolism
D. Digestion
E. Hydrolysis

A

B. Catabolism

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3
Q

Digestion of the macromolecular nutrients (proteins, polysaccharides, and triacylglycerols) to their components involves their:
A. Hydrolysis
B. Reduction
C. Hydration
D. Phosphorylation
E. Condensation

A

A. Hydrolysis

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4
Q

Which of the following is incorrect?
A. Digestion of polysaccharides occurs by the action of amylases
B. Digestion of proteins occurs by the action of several proteases
C. Digestion of triacylglycerols occurs by the action of lipases
D. Digestion products must be stored, since they cannot be degraded any further
E. None; all the other choices are correct

A

D. Digestion products must be stored, since they cannot be degraded any further

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5
Q

Which of the following is incorrect?
A. Glucose can be converted to glycogen, but this cannot be stored
B. Triacylglycerols can be long-term stored in the adipocytes
C. Fatty acids are transported by the protein albumin or linked to cholesterol
D. Glycogen is broken down through phosphorolysis (not hydrolysis)
E. Free fatty acids cannot be stored

A

A. Glucose can be converted to glycogen, but this cannot be stored

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6
Q

Which of the following is incorrect?
A. Metabolic pathways are series of consecutive reactions
B. Metabolic pathways involve mostly intermediates called metabolites
C. A few of the intermediates may be used as precursors
D. Pyruvate cannot be used as a precursor
E. None; all the other choices are correct

A

D. Pyruvate cannot be used as a precursor

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7
Q

Which of the following is incorrect?
A. In carbon dioxide (CO2), C is in the most oxidized form
B. The -(HCOH)- group is more reduced than the -(CH2)- group
C. Less energy can be obtained when oxidizing the -(HCOH)- group than the -(CH2)- group
D. The more reduced a C atom, the more energy can be extracted when oxidized
E. In methane (CH4), C is in the most reduced form

A

B. The -(HCOH)- group is more reduced than the -(CH2)- group

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8
Q

Which of the following is incorrect?
A. Some cofactors undergo oxidation- reduction in metabolism
B. NAD+ accepts electrons in the form of a hydride ion
C. NAD+ contains adenosine
D. NAD+ functions as an electron donor
E. When ubiquinol (QH2) releases electrons, it is being oxidized to ubiquinone (Q)

A

D. NAD+ functions as an electron donor

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9
Q

Which of the following is incorrect?
A. Metabolic pathways are regulated
B. Not all the metabolic pathways are
found in all cells
C. Organisms may be metabolically
interdependent
D. Cells have a unique metabolic
repertoire
E. None; all the other choices are correct

A

E. None; all the other choices are correct

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10
Q

Some amino acids and fatty acids are called “essential” because:
A. They are essential for life
B. They need to be included in our diet
C. They help enzymes perform their
functions
D. They are needed in anabolism
E. They are needed in catabolism

A

B. They need to be included in our diet

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11
Q

Which of the following is incorrect about the free energy change?
A. It is the driving force that reactants experience to reach their equilibrium
B. The biochemical standard state includes a 1 M concentration of all reactants (water included)
C. The biochemical standard state includes pH =7
D. The biochemical standard state includes a temperature of 25 oC (298 K)

A

B. The biochemical standard state includes a 1 M concentration of all reactants (water included)

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12
Q

Which of the following is incorrect when combining ATP hydrolysis and glucose phosphorylation?
A. They represent a coupled process
B. ATP hydrolysis provides the energy for
glucose phosphorylation
C. Phosphorylation of glucose provides
the energy for the hydrolysis of ATP
D. They represent the combination of a
favorable reaction with an unfavorable one E. Phosphorylation of glucose is not a
favorable reaction

A

C. Phosphorylation of glucose provides
the energy for the hydrolysis of ATP

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13
Q

Which of the following is incorrect about the ATP cycle?
A. ATP is generated in catabolism
B. ATP is hydrolyzed in anabolism
C. ATP is hydrolyzed to provide the
energy to degrade the nutrients
D. The cycle refers to the interconversion
between ATP and ADP + Pi
E. None; all the other choices are correct

A

C. ATP is hydrolyzed to provide the
energy to degrade the nutrients

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14
Q

ATP hydrolysis releases a significant amount of energy because of all the following, except:
A. Electrostatic repulsion is lowered in the products
B. Products are resonance-stabilized
C. Products are better hydrated
D. Electrostatic repulsion is increased in
the products

A

D. Electrostatic repulsion is increased in
the products

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15
Q

Which of the following is not a high energy compound? Their free energy change of hydrolysis are between the parentheses.
A. Phosphocreatine (– 43.1 kJ/mol)
B. Phosphoenolpyruvate (– 61.9 kJ/mol)
C. 1,3-Bisphosphoglycerate (– 49.4 kJ/mol)
D. Glucose-1-phosphate (– 20.9 kJ/mol)

A

D. Glucose-1-phosphate (– 20.9 kJ/mol)

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16
Q

Which of the following is incorrect?
A. Regulation of a pathway occurs at steps with large (-) free energy changes
B. Not all the steps of a pathway are regulatory steps
C. Regulation of a pathway occurs at steps with minimal (~ 0) free energy changes
D. Regulatory steps are irreversible
E. None; all the other choices are correct

A

C. Regulation of a pathway occurs at steps with minimal (~ 0) free energy changes

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17
Q

ATP hydrolysis provides the energy for

A

glucose phosphorylation

18
Q

Which of the following is incorrect about glycolysis?
A. It is an anabolic pathway
B. It is the conversion of one glucose to two
pyruvates
C. It has ten steps or reactions divided into two phases
D. It is an energy-generating pathway
E. None; all the other choices are correct

A

A. It is an anabolic pathway

19
Q

Which of the following is incorrect about glycolysis?
A. The 1st phase is called the preparatory or investment phase
B. The 2nd phase is called the payoff phase
C. Some released free energy is “captured” in the form of ATP
D. Some released free energy is “captured” in the form of NAD+
E. The input of ATP occurs in the 1st phase

A

D. Some released free energy is “captured” in the form of NAD+

20
Q

Which of the following is incorrect about the first reaction of glycolysis in which glucose is converted to glucose-6-phosphate?
A. It is a reversible reaction
B. ATP is invested
C. It can be regulated
D. It is catalyzed by hexokinase

A

A. It is a reversible reaction

21
Q

Which of the following is incorrect about the third reaction of glycolysis in which fructose- 6-phosphate is converted to fructose-1,6- bisphosphate?
A. It is an irreversible reaction
B. ATP is invested
C. It is not regulated
D. It is catalyzed by phosphofructokinase (PFK)
E. None; all the other choices are correct

A

C. It is not regulated

22
Q

Which of the following is incorrect about the enzyme that catalyzes the third reaction of glycolysis in which fructose-6-phosphate is converted to fructose-1,6-bisphosphate?
A. ADP activates the enzyme
B. Phosphoenolpyruvate (PEP) inhibits the enzyme
C. Fructose-2,6-bisphosphate activates the enzyme
D. ATP activates the enzyme
E. None; all the other choices are incorrect

A

D. ATP activates the enzyme

23
Q

Which of the following is incorrect about step 6 of glycolysis in which glyceraldehyde- 3-phosphate, Pi, and NAD+ are converted to 1,3-bisphosphoglycerate and NADH?
A. Substrate is phosphorylated without using ATP
B. The aldehyde group is being oxidized
C. Reaction products are considered “high energy” compounds
D. The released electrons are being accepted by NADH
E. None; all the other choices are correct

A

D. The released electrons are being accepted by NADH

24
Q

Which of the following is incorrect about the conversion of pyruvate to acetyl-CoA and
CO2?
A. It is the normal (aerobic) fate of pyruvate
B. It is referred to as an oxidative
decarboxylation
C. Product (acetyl-CoA) is a thioester D. Pyruvate is being decarboxylated
E. It occurs under anaerobic conditions

A

E. It occurs under anaerobic conditions

25
Q

Which of the following is incorrect about the conversion of pyruvate and NADH to lactate and NAD+?
A. It is the normal (aerobic) fate of pyruvate
B. Pyruvate is being reduced
C. Electrons are donated by NADH
D. It occurs in the muscles during exercise
E. It occurs under anaerobic conditions

A

A. It is the normal (aerobic) fate of pyruvate

26
Q

Which of the following is incorrect about the conversion of pyruvate (with 3 C) and CO2 to oxaloacetate (with 4 C) catalyzed by pyruvate carboxylase?
A. Pyruvate is being carboxylated
B. Pyruvate carboxylase is not a regulatory enzyme
C. Pyruvate carboxylase uses biotin
(a vitamin) as a cofactor
D. The reaction is irreversible
E. None; all the other choices are correct

A

B. Pyruvate carboxylase is not a regulatory enzyme

27
Q

Which of the following is incorrect about glycogen synthesis?
A. It starts with glucose-6-phosphate
B. It requires UTP
C. The addition of glucose is catalyzed by glycogen synthase
D. It is not regulated
E. None; all the other choices are correct

A

D. It is not regulated

28
Q

Which of the following is correct about glycogen degradation?
A. It requires ATP
B. It requires UTP
C. Removal of glucose is catalyzed by
glycogen phosphorylase
D. It is not regulated
E. None; all the other choices are incorrect

A

B. It requires UTP

29
Q

Which of the following is incorrect about the pentose phosphate pathway (PPP)?
A. It starts with glucose-6-phosphate
B. A major product is ribose-5-phosphate
C. It generates NADPH for biosynthesis
D. It generates NADH for catabolism
E. None; all the other choices are correct

A

D. It generates NADH for catabolism

30
Q

Which of the following is incorrect about the pyruvate dehydrogenase reaction?
A. It links glycolysis and the citric acid cycle
B. It is not regulated
C. It is an oxidative decarboxylation
D. It is catalyzed by the pyruvate
dehydrogenase complex (PDC)
E. It is irreversible

A

B. It is not regulated

31
Q

Which of the following is incorrect about the cofactors used in the pyruvate dehydrogenase reaction?
A. Thiamine pyrophosphate (TPP) is catalytic since it is recycled
B. Lipoamide has a disulfide bond which is the active portion
C. Coenzyme A is a co-substrate cofactor since it is consumed
D. FAD is a co-substrate cofactor since it is consumed
E. None; all the other choices are correct

A

D. FAD is a co-substrate cofactor since it is consumed

32
Q

Which of the following is incorrect about the mechanism of the pyruvate dehydrogenase reaction?
A. Thiamine pyrophosphate (TPP) having a (-) charge attacks the C=O of pyruvate
B. Coenzyme A having a thiol group attacks the C=O of the acetyl group
C. FAD accepts electrons and transfers them to NAD+
D. NAD+ accepts electrons and transfers them to FAD
E. None; all the other choices are correct

A

D. NAD+ accepts electrons and transfers them to FAD

33
Q

Which of the following is correct about the enzyme that catalyzes the pyruvate dehydrogenase reaction?
A. It is inhibited by acetyl-CoA
B. It is activated by NADH
C. It is inhibited by pyruvate
D. It is activated by acetyl-CoA E. It is activated by ATP

A

A. It is inhibited by acetyl-CoA

34
Q

Which of the following is incorrect about the citric acid cycle?
A. It has three regulatory steps
B. It is highly exergonic
C. The “energy products” are NADH, QH2
and GTP
D. It has three irreversible steps
E. None; all the other choices are correct

A

E. None; all the other choices are correct

35
Q

Which of the following is incorrect about the 1st step of the citric acid cycle in which oxaloacetate is reacted with acetyl-CoA?
A. It is a reversible step
B. It is a condensation
C. It is regulated
D. It is catalyzed by citrate synthase
E. None; all the other choices are correct

A

A. It is a reversible step

36
Q

Which of the following is incorrect about the 3rd step of the citric acid cycle in which isocitrate and NAD+ are converted to α-ketoglutarate, NADH and CO2?
A. It is an oxidative decarboxylation
B. It generates an “energy” compound C. Electrons are collected by NAD+
D. It is not regulated
E. It is irreversible

A

D. It is not regulated

37
Q

Which of the following is incorrect about the 4th step of the citric acid cycle in which a- ketoglutarate, NAD+ and CoA are converted to succinyl-CoA, NADH and CO2?
A. It is an oxidative decarboxylation
B. It generates an “energy” compound C. Electrons are collected by NAD+
D. It is not regulated
E. It is irreversible

A

D. It is not regulated

38
Q

Which of the following is incorrect about the 8th step (conversion of a secondary alcohol group in malate to a keto group in oxaloacetate) of the citric acid cycle?
A. It involves the oxidation of the alcohol group
B. It is not regulated
C. Electrons are collected by NAD+
D. The reaction is irreversible
E. None; all the other choices are correct

A

D. The reaction is irreversible

39
Q

Which of the following is correct?
A. NADH inhibits the citric acid cycle
B. The citric acid cycle is not regulated
C. ADP inhibits the citric acid cycle
D. ATP activates the citric acid cycle
E. None; all the other choices are incorrect

A

A. NADH inhibits the citric acid cycle

40
Q

Which of the following cannot be made from intermediates of the citric acid cycle?
A. Glucose
B. Amino acids
C. Fatty acids
D. Vitamins

A

D. Vitamins

41
Q

Which of the following is incorrect?
A. Citrate can be moved out of the mitochondria to the cytosol
B. In the cytosol, citrate, is split into acetyl-CoA and oxaloacetate
C. Acetyl-CoA in the cytosol is used for lipid biosynthesis
D. None; all the other choices are correct

A

D. None; all the other choices are correct

42
Q

The so-called anaplerotic reactions “replenish” intermediates of the citric acid cycle. Which of the following is the major source of citric acid cycle intermediates?
A. Glucose
B. Amino acids
C. Fatty acids
D. Cholesterol

A

B. Amino acids

XX. BioChemistry (15 decks)

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