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Biochemistry > Discussion 7 > Flashcards

Discussion 7 Flashcards

1
Q

In glycolysis ___ moles of ATP and ___ moles of NADH are produced per one mole of glucose consumption.

1, 2

2, 2

2, 1

1, 1

2, 10

A

2,2

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2
Q

The first committed step in glycolysis is mediated by ___________.

hexokinase

phosphofructokinase

triose phosphate isomerase

pyruvate kinase

A

phosphofructokinase

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3
Q

Which of the following features are common to all anabolic pathways?

They are oxidative.

Their overall free energy change is positive.

They require energy.

They break down complex molecules.

A

They require energy.

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4
Q

Which of the following is a method of directly regulating PFK-1?

Feedback inhibition by fructose-2,6-bisphosphate.

Feed forward activation by phosphoenolpyruvate.

By its phosphorylation in response to glucagon signaling.

Allosteric activation by ADP.

A

Allosteric activation by ADP.

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5
Q

When the energetic level (glucose) of the cell low glycolysis is ___________ and when plasma glucose level is low gluconeogenesis is ___________.

activated; inhibited

activated; activated

inhibited; activated

inhibited; inhibited

none of the above

A

activated; activated

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6
Q

The reactions of glycolysis that are bypassed in gluconeogenesis are catalyzed by the enzymes ___________.

hexokinase, phosphofructokinase, and pyruvate kinase

pyruvate carboxylase, aldolase, and phosphofructokinase

glucose-6-kinase, aldolase and enolase

glucose-6-phosphatase, fructose-1,6-bisphosphatase, pyruvate carboxylase, and phosphoenolpyruvate carboxylase

A

glucose-6-phosphatase, fructose-1,6-bisphosphatase, pyruvate carboxylase, and phosphoenolpyruvate carboxylase

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7
Q

In humans, which one of the following statements about gluconeogenesis is TRUE?

Can result in the conversion of protein into glucose

Helps to reduce blood glucose after a carbohydrate-rich meal

Is essential in the conversion of fatty acids to glucose

Requires the enzyme hexokinase

A

Can result in the conversion of protein into glucose

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8
Q

Which of the following statements regarding gluconeogenesis is TRUE?

Fructose-2,6-bisphosphate activates gluconeogenesis.

It occurs actively in skeletal muscle during periods of exercise.

It is likely to occur when cellular ATP levels are high.

Gluconeogenesis is reciprocally regulated with glycogen synthesis.

The conversion of phosphoenolpyruvate to 2-phosphoglycerate occurs in two steps.

A

It is likely to occur when cellular ATP levels are high.

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9
Q

Pyruvate dehydrogenase, the enzyme that catalyzes the conversion of pyruvate to acetyl-CoA, is a multi-subunit enzyme that requires which of the following vitamins and cofactors?

lipoic acid, thiamine, ferredoxin, vitamin D

thiamine pyrophosphate, lipoamide, nicotine adenine dinucleotide

thiamine, ascorbic acid, niacin, pantothenic acid

ferredoxin, thiamine, niacin, FMN

A

thiamine pyrophosphate, lipoamide, nicotine adenine dinucleotide

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10
Q

Which of the following is NOT a direct product of pyruvate metabolism?

A. Acetyl-CoA

B. Lactate

C. Oxaloacetate

D. Phosphoenolpyruvate

Both C and D are correct.

A

D. Phosphoenolpyruvate

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11
Q

The conversion of triacylglycerides into fatty acids for energy generation is an example of which of the following?

heterotropism

anaerobism

catabolism

anabolism

glycolysis

A

catabolism

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12
Q

Cells control or regulate the flux through metabolic pathways by means of

I. allosteric control of enzymes.
II. covalent modification of enzymes.
III. genetic control of the concentrations of enzymes.
IV. altering the ∆G value of reactions.

I, II, III, IV

II, III

I, II, IV

I, II, III

I, IV

A

I, II, III

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13
Q

In the catabolic pathway, major nutrients are _____ broken down mainly resulting in more _____ metabolites.

exergonically; reduced

endergonically; reduced

exergonically; oxidized

endergonically; oxidized

endergonically; phosphorylated

A

exergonically; oxidized

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14
Q

The products of glycolysis include ATP, NADH, and __________________.

A

Pyruvate.

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15
Q

The enzyme ______________ is the major control point for glycolysis.

A

Pyruvate Kinase or phosphofructokinase.

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16
Q

Which of the following enzymes catalyzes the transfer of a phosphoryl group from ATP to glucose?

hexokinase

phosphoglucose isomerase

glucose-6-phosphatase

phosphoglucose mutase

A transfer such as this does not occur in glycolysis.

A

Hexokinase

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17
Q

Which is the net equation for aerobic glycolysis?

Glucose + 2 ATP → 2 lactate + 2 ADP + 2 Pi

Glucose + 2 ADP + 2 Pi + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH + + 2 H2O + 4 H+

Glucose + 2 ADP + 2 Pi → 2 lactate + 4 ATP + 4 H+

Glucose + 2 ATP + 2 NAD+ → 2 pyruvate + 4 ATP + 4 NADH + 4 H+

Glucose + 2 ADP + 2 Pi + 2 NAD+ → 2 lactate + 4 ATP + 2 NADH + 4 H+

A

Glucose + 2 ADP + 2 Pi + 2 NAD+ → 2 pyruvate + 2 ATP + 2 NADH + + 2 H2O + 4 H+

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18
Q

Of the reaction types listed below, which type of reaction is NOT used in glycolysis?

oxidation

phosphorylation

dehydration

isomerization

All are used in glycolysis.

A

All are used in glycolysis.

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19
Q

During reactions using the enzymes shown below, in which case(s) is ATP produced?

I. phosphofructokinase (PFK)
II. phosphoglycerate kinase (PGK)
III. pyruvate kinase (PK)

I

II

III

I, II

II, III

A

II, III

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20
Q

In which of the following metabolic conversions is ATP required during glycolysis?

I. fructose-6-phosphate → fructose-1,6-bisphosphate
II. glucose → glucose-6-phosphate
III. fructose-1,6-bisphosphate → dihydroxyacetone phosphate + glyceraldehyde-3-phosphate
IV. glucose-6-phosphate → fructose-6-phosphate

I only

II only

I, II

I, III

I, IV

A

I, II

21
Q

The process of _____ converts glucose into _____.

electron transport; CO2

glycolysis; pyruvate

glycogenolysis; glycogen

gluconeogenesis; glycogen

glycogen synthesis; pyruvate

A

glycolysis; pyruvate

22
Q

Hexokinase is an example of a(n) _____ enzyme.

ligase

hydrolase

transferase

lyases

isomerase

A

Transferase

23
Q

Which enzyme is responsible for splitting a hexose into two trioses?

enolase

phosphoglycerate mutase

phosphofructose isomerase

triose phosphate isomerase

aldolase

A

Aldolase

24
Q

Which of the following is a potent activator of phosphofructokinase in mammals?

fructose-6-phosphate

glucose-6-phosphate

fructose-2,6-bisphosphate

fructose-1,6-bisphosphate

glyceraldehyde-3-phosphate

A

fructose-2,6-bisphosphate

25
Q

The active site of aldolase contains a Lys residue that forms a(n) _____ and a(n) Asp residue that participates in _____ reactions.

amide; acid-base

Schiff base; acid-base

secondary amine; acid-base

amide; isomerization

Schiff base; isomerization

A

Schiff base; acid-base

26
Q

Triose phosphate isomerase catalyzes a reaction that is most like that of _____.

phosphoglycerate mutase

phosphoglucose isomerase

hexokinase

aldolase

enolase

A

phosphoglucose isomerase

27
Q

Glyceraldehyde-3-PO4 is oxidized to _____, which can transfer a phosphate to _____.

phosphoenolpyruvate; ADP

phosphoenolpyruvate; AMP

1,3-bisphosphoglycerate; ADP

1,3-bisphosphoglycerate; AMP

3-phosphoglycerate; ADP

A

1,3-bisphosphoglycerate; ADP

28
Q

Why is phosphoglycerate kinase still considered a kinase even though ADP is converted to ATP?

The enzyme is freely reversible.

ATP is the ultimate source of the phosphate that is transferred to ADP.

The phosphate is transferred in conjunction with an oxidation reaction.

The reaction is metabolically irreversible.

None of the above

A

The enzyme is freely reversible.

29
Q

In which reaction below is ATP required?

I. 1,3-bisphosphoglycerate (BPG) → 3-phosphoglycerate(3PG)
II. Glucose → glucose-6-phosphate (G6P)
III. 2-Phosphoglycerate (2PG) → 3-phosphoglycerate (3PG)
IV. Glyceraldehyde-3-phosphate (GAP) → 1,3-bisphosphoglycerate (BPG)
V. Glucose-6-phosphate (G6P) → fructose-6-phosphate (F6P)

I, II

II only

III only

IV, V

None of the reactions I-V requires ATP.

A

II only

30
Q

Which reaction below is an oxidation reaction?

I. 1,3-bisphosphoglycerate (BPG) → 3-phosphoglycerate(3PG)
II. Glucose → glucose-6-phosphate (G6P)
III. 2-Phosphoglycerate (2PG) → 3-phosphoglycerate (3PG)
IV. Glyceraldehyde-3-phosphate (GAP) → 1,3-bisphosphoglycerate (BPG)
V. Glucose-6-phosphate (G6P) → fructose-6-phosphate (F6P)

I, III

II, III

III only

IV only

None of reactions I–V is oxidation reactions.

A

IV only

31
Q

In which reaction below is at least one NADH formed?

I. 1,3-bisphosphoglycerate (BPG) → 3-phosphoglycerate(3PG)
II. Glucose → glucose-6-phosphate (G6P)
III. 2-Phosphoglycerate (2PG) → 3-phosphoglycerate (3PG)
IV. Glycerol-3-phosphate (GAP) → 1,3-bisphosphoglycerate (BPG)
V. Glucose-6-phosphate (G6P) → fructose-6-phosphate (F6P)

II only

III only

IV only

IV, V

None of reaction I–V forms NADH.

A

IV only

32
Q

What type of enzyme is enolase, which catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate and water?

transferase

hydrolase

ligase

lyase

oxidoreductase

A

Lyase

33
Q

What sort of activity does fructose-1,6-bisphosphate have on pyruvate kinase?

no effect

competitive inhibitor

noncompetitive inhibitor

allosteric inhibitor

activator

A

activator

34
Q

Phosphofructokinase is allosterically _____ by high concentrations of _____.

I. activated; ATP
II. inhibited; ATP
III. inhibited; fructose-2,6-bisphosphate
IV. activated; fructose-2,6-bisphosphate

I, III

II, III

II, IV

I, IV

none of the above

A

II, IV

35
Q

Which of the following metabolic conversions is considered the major control point of glycolysis?

fructose-1,6-bisphosphate → dihydroxyacetone phosphate + glyceraldehyde-3-phosphate

glucose → glucose-6-phosphate

2-phosphoglyerate → phosphoenolpyruvate

fructose-6-phosphate → fructose-1,6-bisphosphate

phosphoenolpyruvate → pyruvate

A

fructose-6-phosphate → fructose-1,6-bisphosphate

36
Q

Which of the following is true regarding glycolysis?

I. There is a net oxidation of substrate carbon atoms.
II. There is no net release of free energy.
III. Pyruvate is generated only during aerobic glycolysis.
IV. There are 2 ATP formed for every 2 glucose molecules.

I only

I, IV

I, III, IV

IV only

II, IV

A

I only

37
Q

The reaction catalyzed by the enzyme aldolase has a G˚’ ≈ +23 kJ/mol. In muscle cells, the reaction proceeds in this same, forward direction. How can this occur?

This G˚’ means it is thermodynamically favored.

The enzyme changes the ∆G of the reaction in cells to something favorable.

The concentration of reactant(s) must be significantly greater than product(s) in cells.

The concentration of product(s) must be significantly greater than reactant(s) in cells.

None of the above

A

The concentration of reactant(s) must be significantly greater than product(s) in cells.

38
Q

Which of the following best describes the entry of mannose into glycolysis?

hydrolyzed into two glucose units, they enter normally

phosphorylated at C-1; UMP moiety transferred from UDP-glucose; epimerized at C-2; released from UMP moiety on next transfer as G1P

phosphorylated at C-1; UMP moiety transferred from UDP-glucose; epimerized at C-4; released from UMP moiety on next transfer as G1P

phosphorylated at C-6; epimerized at C-2 to produce G6P

phosphorylated at C-6; isomerized to produce F6P

A

phosphorylated at C-6; isomerized to produce F6P

39
Q

What pathway is used to make glucose from other metabolites such as pyruvate or lactate?

glycogen synthesis

glycogen degradation

glycolysis

pentose phosphate pathway

gluconeogenesis

A

gluconeogenesis

40
Q

How many equivalents of ATP are required to convert two molecules of pyruvate to glucose?

2

4

6

8

10

A

6

41
Q

Gluconeogenesis is most active in the _____.

muscles

brain

heart

liver

kidneys

A

Liver

42
Q

Which of the following is true concerning the reaction catalyzed by pyruvate dehydrogenase?

It is an oxidative decarboxylation.

It is activated by high concentrations of ATP.

The enzyme contains a pyridoxal phosphate prosthetic group.

The reaction is an anaplerotic reaction because it can replace citric acid intermediates that are removed for other pathways.

The enzyme contains two different types of subunits.

A

It is an oxidative decarboxylation.

43
Q

Which of the following is an inhibitor of pyruvate dehydrogenase?

CoA

pyruvate

FADH2

NADH

CO2

A

NADH

44
Q

Under aerobic conditions, pyruvate is converted to _____ by pyruvate dehydrogenase.

oxaloacetate

ethanol

lactate

glucose

acetyl-CoA

A

Acetyl-CoA

45
Q

What cellular location contains pyruvate dehydrogenase and most of the citric acid cycle enzymes?

cytosol

mitochondrial matrix

inner mitochondrial membrane

mitochondrial intermembrane space

outer mitochondrial membrane

A

mitochondrial matrix

46
Q

Under anaerobic conditions in skeletal muscle, pyruvate is converted into _____.

ethanol and CO2

propionate

acetyl-CoA

lactate

alanine

A

lactate

47
Q

Glycolysis forms ______________ under either aerobic or anaerobic conditions.

A

ATP

48
Q

In skeletal muscle cells, oxidation of NADH generated from anaerobic glycolysis occurs during which of the following reactions?

acetaldehyde → ethanol

lactate → pyruvate

phosphoenolpyruvate → pyruvate

pyruvate → lactate

glyceraldehyde-3-phosphate → 1,3-bisphosphoglycerate

A

pyruvate → lactate

Biochemistry (32 decks)

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