Biochemistry Chapter 14

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1

Ultimate electron acceptor in fermentation of glucose to ethanol is:

Acetaldehyde

2

In alcoholic fermentation of glucose by yeast, thiamine pyrophosphate is required by:

Pyruvate decarboxylase

3

What cannot serve as starting material for synthesis of glucose via gluconeogenesis?

Acetate

4

What CAN serve as starting material for synthesis of glucose via gluconeogenesis?

Glycerol,
Lactate,
Oxaloacetate,
α-ketoglutarate

5

Enzyme used in both glycolysis and gluconeogenesis is:

3-phosphoglycerate kinase

6

All of the following enzymes involved in the flow of carbon from glucose to lactate "(glycolysis) are also involved in reversal (gluconeogenesis) except: 1) 3-phosphoglycerate kinase
2) aldolase
3) enolase
4) phosphofructokinase
5) phosphoglucoisomerase

phosphofructokinase

7

In humans, gluconeogenesis:

can result in conversion of protein into blood glucose

8

What substrate cant contribute to net gluconeogenesis in mammalian liver?

palmitate

9

T/F: Pentose phosphate pathway provides precursors for synthesis of nucleotides

True

10

Main function of pentose pathway pathway is to:

supply pentoses and NADPH

11

Metabolic function of pentose phosphate pathway is:

generate NADPH and pentoses for biosynthesis of fatty acids and nucleic acids

12

T/F: Pentose phosphate pathway requires participation of molecular oxygen

False

13

Glucose breakdown in certain mammalian and bacterial cells can occur by mechanisms other than classic glycolysis. In most of these, glucose 6-phosphate is oxidized to 6-phosphogluconate, which is futher metabolized by:

Decarboxylation to produce keto- and aldopentoses

14

What is one enzyme acts in pentose phosphate pathway?

6-phosphogluconate dehydrogenase

15

Oxidation of 3 mol of glucose by pentose phosphate pathway may result in production of:

3 mol of pentose, 6 mol of NADPH, 3 mol of CO2

16

Glucose, labeled with 14C in different carbon atoms, is added to crude extract of a tissue rich in enzymes of pentose phosphate pathway. The most rapid production of 14CO2 will occur when glucose is labeled in:

C-1

17

In tissue that metabolizes glucose via pentose phosphate pathway, C-1 of glucose would be expected to end up in:

carbon dioxide

18

Glycolysis is an example of:

fermentation

19

anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied by net gain of:

2 mol of ATP

20

During exercise, NADH formed in glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis were to continue. Most important reaction involved in reoxidation of NADH is:

Pyruvate --> lactate

21

If glucose labeled with 14C in C-1 were fed to yeast carrying out the ethanol fermentation, where would 14C be in products?

C-2 (methyl group) of ethanol only

22

conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol pyruvate by glycolytic pathway results in net formation of:

2 mol of NADH and 4 mol of ATP

23

In anaerobic muscle preparation, lactate formed from glucose labeled in C-3 and C-4 would be labeled in

only Carboxyl carbon atom

24

T/F: Glycolysis in anaerobic muscle is an endergonic process

False

25

When muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts anaerobically because:

under aerobic conditions most of pyruvate generated as a result of glycolysis is oxidized by citric acid cycle rather than reduced to lactate

(aerobically --> oxidized; anaerobically --> reduced)

26

Glycolysis in erythrocyte produces pyruvate that is further metabolized to:

lactate

27

Glucose labeled with 14 C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:

methyl carbon

28

Glucose labeled with 14C at C-1 (aldehyde carbon) were metabolized in liver, first radioactive pyruvate formed would be labeled in:

methyl carbon

29

In anaerobic muscle prep, lactate formed from glucose labeled in C-2 would be labeled in:

only carbon atom carrying OH

30

Glucose labeled with 14C in C-3 is metabolized to lactate via fermentation, lactate wil contain 14C in:

carboxyl carbon atom

31

What cofactor participates directly in most oxidation-reduction reactions in fermentation of glucose to lactate?

NAD+ / NADH

32

In comparison with resting state, actively contracting human muscle tissue has a:

higher rate of lactate formation

33

Steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate do not involve:

oxidation of NADH to NAD+

34

First reaction in glycolysis that results in formation of energy-rich compound is catalyzed by:

glyceraldehyde 3-phosphate dehydrogenase

35

Which is cofactor in reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

NAD+

36

In phosphoglycerate muscle reaction, the side chain of which amino acid in enzyme is phosphorylated as part of reaction?

histidine

37

Inorganic fluoride inhibits enolase. In anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride?

2-phosphoglycerate

38

Glycogen is converted to monosaccharide units by:

Glycogen phosphorylase

39

T/F: Under anaerobic conditions, pyruvate doe not form because glycolysis does not occur

False

40

Which of the following steps occurs during the payoff phase of glycolysis?

A) the conversion of fructose 6-phosphate to fructose 1,6-biphosphate
B) the conversion of phosphoenolpyruvate to pyruvate
C) the conversion of glucose to glucose 6-phosphate
D) the conversion of glucose 6-phosphate to fructose 6-phosphate

B) the conversion of phosphoenolpyruvate to pyruvate

41

The phosphorylation of glucose to glucose-6-phosphate has a free energy change of +3.3 kcal/mol. So why does the reaction occur in almost every cell of our body?

A) Hexokinase is present.
B) Glucose becomes unstable intracellularly.
C) This reaction is coupled to another that has a much higher positive free energy change.
D) It is coupled to ATP hydrolysis.

NOT A.( Hexokinase)

42

In glycolysis, fructose-1,6-bisphosphate is converted to two products with a standard free-energy change (ΔG°') of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change (ΔG) be negative, enabling the reaction to proceed to the right?

A) Under standard conditions, enough energy is released to drive the reaction to the right.
B) If the concentrations of the two products are high relative to that of fructose-1,6-bisphosphate.
C) The reaction will not go to the right spontaneously under any conditions because ΔG°' is positive.
D) When there is a high concentration of fructose-1,6-bisphosphate relative to the concentration of products.
E) When there is a high concentration of products relative to the concentration of fructose-1,6-bisphosphate.

D) When there is a high concentration of fructose-1,6-bisphosphate relative to the concentration of products.

43

The first committed step in the glycolytic pathway is the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate.
True/ False

True

44

In the conversion of glucose to pyruvate via glycolysis, all of the following enzymes participate. Number the following enzymes 1 through 7 in the order in which they function.

_a_phosphofructokinase-1
_b_pyruvate kinase
_c_phosphoglycerate kinase
_d_triose phosphate isomerase
_e_phosphohexose isomerase
_f_glyceraldehyde-3-phosphate dehydrogenase
_g_phosphoglycerate mutase

e, a, d, f, c, g, b

45

The conversion of 2-phosphoglycerate to phosphoenolpyruvate is:

A) a reduction.
B) a lysis.
C) an oxidation.
D) an isomerization.
E) a dehydration.

E) a dehydration.

46

Which of these cofactors participates directly in most of the oxidation-reduction reactions in the fermentation of glucose to lactate?

A) glyceraldehyde-3-phosphate
B) FAD/FADH2
C) ATP
D) NAD+/NADH
E) ADP

D) NAD+/NADH

47

Gluconeogenesis differs from glycolysis because:
A) the irreversible steps of glycolysis are bypassed.
B) different enzymes are involved.
C) biotin is required for gluconeogenesis and not for glycolysis.
D) all of the above.
E) none of the above.

D) all of the above.

48

Mitochondria participate in the glycolytic pathway but not in the gluconeogenic pathway.

True/False

False

49

Gluconeogenesis must use "bypass reactions" to circumvent three reactions in the glycolytic pathway that are highly exergonic and essentially irreversible. Reactions carried out by which three enzymes must be bypassed in the gluconeogenic pathway?
A) hexokinase, phosphoglycerate kinase, phosphofructokinase-1
B) hexokinase, pyruvate kinase, triose phosphate isomerase
C) phosphoglycerate kinase, phosphofructokinase-1, pyruvate kinase
D) hexokinase, phosphofructokinase-1, pyruvate kinase
E) hexokinase, phosphoglycerate kinase, pyruvate kinase

D) hexokinase, phosphofructokinase-1, pyruvate kinase

50

The endoplasmic reticulum bound enzyme that hydrolyzes glucose-6-phosphate to glucose in liver is:
A) hexokinase.
B) phosphoglucomutase.
C) glucose oxidase.
D) glucose-6-phosphatase.
E) glucokinase.

NOT C

51

Glycolysis and the pentose phosphate pathway are the same in that:
A) they both generate NADH.
B) they both generate ATP.
C) they both involve oxidation of glucose.
D) they are reversible.

NOT b 

52

Which of the following enzymes acts in the pentose phosphate pathway?
A) pyruvate kinase
B) aldolase
C) 6-phosphogluconate dehydrogenase
D) glycogen phosphorylase
E) phosphofructokinase-1

C) 6-phosphogluconate dehydrogenase

53

Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. Glycolysis is an example of:

A) aerobic metabolism.
B) anabolic metabolism.
C) a net reductive process.
D) fermentation.
E) oxidative phosphorylation.

D) fermentation.

54

The anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied by a net gain of:

A) 1 mol of ATP.
B) 1 mol of NADH.
C) 2 mol of ATP.
D) 2 mol of NADH.
E) none of the above.

C) 2 mol of ATP.

55

During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most important reaction involved in the reoxidation of NADH is:

A) dihydroxyacetone phosphate → glycerol 3-phosphate
B) glucose 6-phosphate → fructose 6-phosphate
C) isocitrate → α-ketoglutarate
D) oxaloacetate → malate
E) pyruvate → lactate

E) pyruvate → lactate

56

The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of:

A) 1 mol of NAD+ and 2 mol of ATP.
B) 1 mol of NADH and 1 mol of ATP.
C) 2 mol of NAD+ and 4 mol of ATP.
D) 2 mol of NADH and 2 mol of ATP.
E) 2 mol of NADH and 4 mol of ATP.

E) 2 mol of NADH and 4 mol of ATP.

57

Which of the following statements is not true concerning glycolysis in anaerobic muscle?

A) Fructose 1,6-bisphosphatase is one of the enzymes of the pathway.
B) It is an endergonic process.
C) It results in net synthesis of ATP.
D) It results in synthesis of NADH.
E) Its rate is slowed by a high [ATP]/[ADP] ratio.

B) it is an endergonic process.

58

When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts anaerobically because:

A) glycolysis does not occur to significant extent under aerobic conditions.
B) muscle is metabolically less active under aerobic than anaerobic conditions.
C) the lactic acid generated is rapidly incorporated into lipids under aerobic conditions.
D) under aerobic conditions in muscle, the major energy-yielding pathway is the pentose phosphate pathway, which does not produce lactate.
E) under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidized by the citric acid cycle rather than reduced to lactate.

E) under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidized by the citric acid cycle rather than reduced to lactate.

59

Glycolysis in the erythrocyte produces pyruvate that is further metabolized to:

A) CO2.
B) ethanol.
C) glucose.
D) hemoglobin.
E) lactate.

E) lactate.

60

When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which one of the following statements is most nearly correct, when applied to the reaction below (R = 8.315 J/mol·K and T = 298 K)?

Glucose 6-phosphate ↔ fructose 6-phosphate

A) ΔG'° is +1.7 kJ/mol.
B) ΔG'° is -1.7 kJ/mol.
C) ΔG'° is incalculably large and negative.
D) ΔG'° is incalculably large and positive.
E) ΔG'° is zero.

A) ΔG'° is +1.7 kJ/mol.

61

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change (ΔG'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change (ΔG) be negative, enabling the reaction to proceed to the right?

A) If the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate.
B) The reaction will not go to the right spontaneously under any conditions because the ΔG'° is positive.
C) Under standard conditions, enough energy is released to drive the reaction to the right.
D) When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.
E) When there is a high concentration of products relative to the concentration of fructose 1,6-bisphosphate.

D) When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.

62

Which of these cofactors participates directly in most of the oxidation-reduction reactions in the fermentation of glucose to lactate?

A) ADP
B) ATP
C) FAD/FADH2
D) Glyceraldehyde 3-phosphate
E) NAD+/NADH

E) NAD+/NADH

63

In comparison with the resting state, actively contracting human muscle tissue has a:

A) higher concentration of ATP.
B) higher rate of lactate formation.
C) lower consumption of glucose.
D) lower rate of consumption of oxygen
E) lower ratio of NADH to NAD+.

B) higher rate of lactate formation.

64

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except:

A) ATP synthesis.
B) catalysis by phosphoglycerate kinase.
C) oxidation of NADH to NAD+.
D) the formation of 1,3-bisphosphoglycerate.
E) utilization of Pi.

C) oxidation of NADH to NAD+.

65

The first reaction in glycolysis that results in the formation of an energy-rich compound (i.e., a compound whose hydrolysis has a highly negative ΔG'°) is catalyzed by:

A) glyceraldehyde 3-phosphate dehydrogenase.
B) hexokinase.
C) phosphofructokinase-1.
D) phosphoglycerate kinase.
E) triose phosphate isomerase.

A) glyceraldehyde 3-phosphate dehydrogenase.

66

Which of the following is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

A) ATP
B) Cu2+
C) heme
D) NAD+
E) NADP+

D) NAD+

67

Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride?

A) 2-phosphoglycerate
B) Glucose
C) Glyoxylate
D) Phosphoenolpyruvate
E) Pyruvate

A) 2-phosphoglycerate

68

Glycogen is converted to monosaccharide units by:

A) glucokinase.
B) glucose-6-phosphatase
C) glycogen phosphorylase.
D) glycogen synthase.
E) glycogenase.

C) glycogen phosphorylase.

69

Which of the following statements is incorrect?

A) Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle.
B) In anaerobic muscle, pyruvate is converted to lactate.
C) In yeast growing anaerobically, pyruvate is converted to ethanol.
D) Reduction of pyruvate to lactate regenerates a cofactor essential for glycolysis.
E) Under anaerobic conditions pyruvate does not form because glycolysis does not occur.

E) Under anaerobic conditions pyruvate does not form because glycolysis does not occur.

70

The ultimate electron acceptor in the fermentation of glucose to ethanol is:

A) acetaldehyde.
B) acetate.
C) ethanol.
D) NAD+.
E) pyruvate.

A) acetaldehyde.

71

In the alcoholic fermentation of glucose by yeast, thiamine pyrophosphate is a coenzyme required by:

A) aldolase.
B) hexokinase.
C) lactate dehydrogenase.
D) pyruvate decarboxylase.
E) transaldolase.

D) pyruvate decarboxylase.

72

Which of the following compounds cannot serve as the starting material for the synthesis of glucose via gluconeogenesis?

A) acetate
B) glycerol
C) lactate
D) oxaloacetate
E) α-ketoglutarate

A) acetate

73

An enzyme used in both glycolysis and gluconeogenesis is:

A) 3-phosphoglycerate kinase.
B) glucose 6-phosphatase.
C) hexokinase.
D) phosphofructokinase-1.
E) pyruvate kinase.

A) 3-phosphoglycerate kinase.

74

Which one of the following statements about gluconeogenesis is false?

A) For starting materials, it can use carbon skeletons derived from certain amino acids.
B) It consists entirely of the reactions of glycolysis, operating in the reverse direction.
C) It employs the enzyme glucose 6-phosphatase.
D) It is one of the ways that mammals maintain normal blood glucose levels between meals.
E) It requires metabolic energy (ATP or GTP).

B) It consists entirely of the reactions of glycolysis, operating in the reverse direction.

75

All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis) are also involved in the reversal of this flow (gluconeogenesis) except:

A) 3-phosphoglycerate kinase.
B) aldolase.
C) enolase.
D) phosphofructokinase-1.
E) phosphoglucoisomerase.

D) phosphofructokinase-1.

76

In humans, gluconeogenesis:

A) can result in the conversion of protein into blood glucose.
B) helps to reduce blood glucose after a carbohydrate-rich meal.
C) is activated by the hormone insulin
D) is essential in the conversion of fatty acids to glucose.
E) requires the enzyme hexokinase.

A) can result in the conversion of protein into blood glucose.

77

Which of the following substrates cannot contribute to net gluconeogenesis in mammalian liver?

A) alanine
B) glutamate
C) palmitate
D) pyruvate
E) α-ketoglutarate

C) palmitate

78

Which of the following statements about the pentose phosphate pathway is correct?

A) It generates 36 mol of ATP per mole of glucose consumed.
B) It generates 6 moles of CO2 for each mole of glucose consumed
C) It is a reductive pathway; it consumes NADH.
D) It is present in plants, but not in animals.
E) It provides precursors for the synthesis of nucleotides

E) It provides precursors for the synthesis of nucleotides.

79

The main function of the pentose phosphate pathway is to:

A) give the cell an alternative pathway should glycolysis fail.
B) provide a mechanism for the utilization of the carbon skeletons of excess amino acids.
C) supply energy.
D) supply NADH.
E) supply pentoses and NADPH.

E) supply pentoses and NADPH.

80

The metabolic function of the pentose phosphate pathway is:

A) act as a source of ADP biosynthesis.
B) generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.
C) participate in oxidation-reduction reactions during the formation of H2O.
D) provide intermediates for the citric acid cycle.
E) synthesize phosphorus pentoxide.

B) generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.

81

Which of the following statements about the pentose phosphate pathway is incorrect?

A) It generates CO2 from C-1 of glucose.
B) It involves the conversion of an aldohexose to an aldopentose.
C) It is prominant in lactating mammary gland.
D) It is principally directed toward the generation of NADPH.
E) It requires the participation of molecular oxygen.

E) It requires the participation of molecular oxygen.

82

Which of the following enzymes acts in the pentose phosphate pathway?

A) 6-phosphogluconate dehydrogenase
B) Aldolase
C) Glycogen phosphorylase
D) Phosphofructokinase-1
E) Pyruvate kinase

A) 6-phosphogluconate dehydrogenase

83

The oxidation of 3 mol of glucose by the pentose phosphate pathway may result in the production of:

A) 2 mol of pentose, 4 mol of NADPH, and 8 mol of CO2.
B) 3 mol of pentose, 4 mol of NADPH, and 3 mol of CO2.
C) 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2.
D) 4 mol of pentose, 3 mol of NADPH, and 3 mol of CO2.
E) 4 mol of pentose, 6 mol of NADPH, and 6 mol of CO2.

C) 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2.