Deck 25: The Chemistry of Metabolism

Question 1

Why are nucleophiles more readily phosphorylated by ATP than by hydrogen phosphate?

Answer 1

Attack on ATP occurs more readily because the leaving group is a weaker base than the hydroxide leaving group were hydrogen phosphate used.

Question 2

A phosphoanhydride bond is known as a ________ bond.

A)low-energy
B)high-energy
C)hydrogen
D)disulfide
E)pericyclic

Answer 2

high-energy

Question 3

The DG°' of the hydrolysis of ATP is ________ kJ/mol.

A)+25.2
B)+7.6
C)-1.0
D)-30.5
E)-225.8

Answer 3

-30.5

Question 4

What carbon of the ribose residue in ATP is phosphorylated?

A)anomeric center
B)5'
C)4'
D)3'
E)2'

Question 5

What explains the kinetic stability of ATP in aqueous media at biological pH?

Question 6

What compounds are formed when a carboxylate is phosphorylated by the attack at the a-phosphorus of ATP?

Question 7

At biological pH, ADP has ________ negative charges per molecule.

A)4)0
B)3)3
C)2)8
D)1)1
E)0)6

Question 8

What compounds are formed when a carboxylate is phosphorylated by the attack at the g-phosphorus of ATP?

Question 9

Draw the chair form of the compound that results when D-glucopyranose reacts with ATP in the presence of an enzyme that catalyzes the phosphorylation of the 6-OH group.

Question 10

Describe what's happening mechanistically when glucose reacts with ATP to yield glucose-6-phosphate.

Question 11

What compounds are formed when a carboxylate is phosphorylated by the attack at the b-phosphorus of ATP?

Question 12

How does production of pyrophosphate as the byproduct in a phosphorylation mechanism result in irreversibility of the transfer?

Question 13

Why does phosphorylating a carboxylate make it more susceptible to nucleophilic attack?

Question 14

To what reaction are many endergonic metabolic processes coupled in order to make them exergonic?

Question 15

Complete the following concerning ATP's role as the universal carrier of chemical energy: "The energy ________ from the hydrolysis of ATP converts ________ reactions into ________ reactions."

A)released, exergonic, endergonic
B)released, endergonic, exergonic
C)consumed, exergonic, endergonic
D)consumed, endergonic, exergonic
E)consumed, oxidation, reduction

Question 16

What organic compound is the most important form of chemical energy?

Question 17

Among those listed below, identify all the phosphoryl transfer reactions.

A)Nucleophile attacks the a-phosphorus.
B)Nucleophile attacks the b-phosphorus.
C)Nucleophile attacks the g-phosphorus.
D)Nucleophile attacks the adenosine.
E)Nucleophile attacks the oxygen attached to the adenosine.

Question 18

What three factors contribute to the greater stability of ADP and phosphate compared to ATP?

Question 19

At biological pH, ATP has ________ negative charges per molecule.

A)4)0
B)3)3
C)2)8
D)1)1
E)0)6

Question 20

What chemical interactions allow certain enzymes to catalyze the hydrolysis of ATP?

Question 21

What coenzymes are required for the b-oxidation pathway?

A)CoASH only
B)FAD and CoASH only
C)NAD⁺ and FAD only
D)NAD⁺ and CoASH only
E)FAD, NAD⁺, and CoASH

Question 22

Give the number of ATP molecules formed from NADH in the fourth stage of catabolism.

A)one
B)two
C)three
D)four
E)none

Question 23

In the first stage of catabolism, carbohydrates are hydrolyzed to ________.

Question 24

In which stage of catabolism is the citric acid cycle found?

Question 25

What enzyme catalyzes the conversion of glycerol-6-phosphate to dihydroxyacetone phosphate?

Question 26

In what three areas of the body does first stage catabolism primarily occur?

Question 27

In the first stage of catabolism, fats are hydrolyzed to ________ and ________.

Question 28

In order to enter the citric acid cycle, a compound must be either an intermediate of the cycle or what other two molecules?

Question 29

Most of the energy provided by chemical nutrients is provided in what stage of catabolism?

Question 30

What class of enzyme puts a phosphoryl group on its substrate?

Question 31

Each passage through the b-oxidation pathway removes ________ carbons from the fatty acyl-CoA.

A)2
B)3
C)4
D)6
E)8

Question 32

In the first stage of catabolism, proteins are hydrolyzed to ________.

Question 33

In the citric acid cycle, each molecule of acetyl-CoA is converted into two molecules of what?

A)oxygen
B)pyruvate
C)lactic acid
D)acetone
E)carbon dioxide

Question 34

Identify the steps that occur in catabolism.

A)Fats, carbohydrates, and proteins are hydrolyzed.
B)digestion
C)NADH is converted to ATP.
D)citric acid cycle
E)All steps occur.

Question 35

Fatty acyl-CoA is converted to acteyl-CoA in a repeating pathway called ________.

A)glycolysis
B)b-oxidation
C)oxidative phosphorylation
D)the citric acid cycle
E)phosphoryl transfer

Question 36

The first reaction in the b-oxidation pathway produces ________.

A)an a,b-unsaturated fatty acyl-CoA
B)a b-hydroxy fatty acyl-CoA
C)an a-hydroxy fatty acyl-CoA
D)a b-keto fatty acyl-CoA
E)an a-keto fatty acyl-CoA

Question 37

The fourth step in the b-oxidation is a reverse ________.

A)Claisen condensation
B)aldol condensation
C)Michael addition
D)Diels Alder reaction
E)saponification

Question 38

Give the number of carbon dioxide molecules formed from each molecule of acetyl-CoA in the citric acid cycle.

A)one
B)two
C)three
D)four
E)none

Question 39

In the second stage of catabolism, compounds are converted into molecules that can directly enter ________.

A)the pyruvate dehydrogenase system
B)the citric acid cycle
C)glycolysis
D)the tyrosine aminotransferase pathway
E)the oxidative phosphorylation pathway

Question 40

________ is the only non-citric acid cycle intermediate that can enter the cycle.

A)vitamin A
B)acetyl-CoA
C)thiamine
D)tyrosine
E)glycerol

Question 41

Give the product for the following reaction.

A)
B)
C)
D)
E)

Question 42

Give the product(s)for the following reaction.

A)
B)
C)
D)
E)

Question 43

In glycolysis, each molecule of glucose is converted to two molecules of ________.

A)pyruvate
B)acetaldehyde
C)1,3-dihydroxyacetone
D)acetyl-CoA
E)glycerol

Question 44

What coenzyme is required to facilitate the conversion of glycerol-3-phosphate into dihydroxyacetone?

Question 45

Which step of the b-oxidation pathway is a conjugate addition of water to the organic substrate?

Question 46

Give the product(s)formed from the hydrolysis of a fat.

A)esters
B)aldehydes
C)glycerol
D)fatty acids
E)ketones

Question 47

Draw the structure of a fatty acyl-CoA.

Question 48

In glycolysis, what type of reaction converts the 6-carbon intermediate into two 3-carbon intermediates?

A)reverse aldol condensation
B)reverse Claisen condensation
C)a reverse Michael addition
D)a reverse Diels Alder reaction
E)a transesterification reaction

Question 49

Acetyl-CoA enters the citric acid cycle by reacting with ________ to form ________.

Question 50

Under anaerobic conditions, what compound in mammalian cells is used to oxidize NADH back to NAD⁺ so that glycolysis can continue?

Question 51

In glycolysis, conversion of a molecule of glucose into 2 molecules of pyruvate results in a net production of ________ molecules of ATP.

A)2
B)3
C)4
D)6
E)12

Question 52

Causing a burning sensation in the muscles, what compound builds up in muscle cells when glycolysis occurs under anaerobic conditions?

Question 53

Under anaerobic conditions in yeast cells, pyruvate is converted to acetaldehyde and ________, with the acetaldehyde being subsequently converted to ________ in a step that reoxidizes NADH to NAD⁺.

Question 54

Draw the structure of pyruvate.

Question 55

Of the following compounds, which are consumed in any step of the glycolytic conversion of glucose to pyruvate: ATP, ADP, NAD⁺, NADH, FAD, FADH₂, Acetyl-CoA.

Question 56

Of the following compounds, which are generated in any step of the glycolytic conversion of glucose to pyruvate: ATP, ADP, NAD⁺, NADH, FAD, FADH₂, acetyl-CoA.

Question 57

What coenzyme is required in the conversion of glycerol-6-phosphate to dihydroxyacetone phosphate?

Question 58

Under normal aerobic conditions in mammalian cells, into what two compounds is the pyruvate generated in glycolysis converted?

Question 59

Give the product from the beta-oxidation of a fatty acyl-CoA.

Question 60

What is the final product from the glycolysis of glucose?

A)one molecule of pyruvate
B)two molecules of pyruvate
C)one molecule of 3-phosphoglycerate
D)one molecule of 2-phosphoglycerate
E)one molecule of glyceraldehyde-3,P

Question 61

How many citric acid cycles would be needed to produce nine molecules of FADH₂?

A)nine citric acid cycles
B)one citric acid cycle
C)two citric acid cycles
D)four citric acid cycles
E)three citric acid cycles

Question 62

How many citric acid cycles would be needed to produce nine molecules of NADH?

A)nine citric acid cycles
B)one citric acid cycle
C)two citric acid cycles
D)four citric acid cycles
E)three citric acid cycles

Question 63

Identify the first step of the citric acid cycle.

A)Citrate is converted to isocitrate.
B)Conjugate addition of water to the double bond of fumarate forms (S)-malate.
C)Acetyl-CoA reacts with oxaloacetate to form citrate.
D)FAD oxidizes succinate to fumarate.
E)The secondary alcohol of isocitrate is oxidized to a ketone by NAD⁺ and the ketone loses CO₂.

Question 64

Identify the seventh step of the citric acid cycle.

A)Citrate is converted to isocitrate.
B)Conjugate addition of water to the double bond of fumarate forms (S)-malate.
C)Acetyl-CoA reacts with oxaloacetate to form citrate.
D)FAD oxidizes succinate to fumarate.
E)The secondary alcohol of isocitrate is oxidized to a ketone by NAD⁺ and the ketone loses CO₂.

Question 65

Each round of the citric acid cycle forms ________ molecule(s)of NADH.

A)3
B)0
C)1
D)2
E)4

Question 66

In the citric acid cycle, what type of intermediate occurs as succinyl-CoA is converted into succinate?

A)an acyl phosphate
B)isocitrate
C)a-ketoglutarate
D)an aminophosphate
E)an acyl radical

Question 67

For each molecule of FADH₂ that undergoes oxidative phosphorylation, ________ molecule(s)of ATP is (are)formed.

A)2
B)0
C)1
D)3
E)4

Question 68

Identify the third step of the citric acid cycle.

A)Citrate is converted to isocitrate.
B)Conjugate addition of water to the double bond of fumarate forms (S)-malate.
C)Acetyl-CoA reacts with oxaloacetate to form citrate.
D)FAD oxidizes succinate to fumarate.
E)The secondary alcohol of isocitrate is oxidized to a ketone by NAD⁺ and the ketone loses CO₂.

Question 69

How many molecules of ATP are formed by the citric acid cycle from one molecule of acetyl-CoA?

Question 70

Identify the sixth step of the citric acid cycle.

A)Citrate is converted to isocitrate.
B)Conjugate addition of water to the double bond of fumarate forms (S)-malate.
C)Acetyl-CoA reacts with oxaloacetate to form citrate.
D)FAD oxidizes succinate to fumarate.
E)The secondary alcohol of isocitrate is oxidized to a ketone by NAD⁺ and the ketone loses CO₂.

Question 71

In the citric acid cycle, the acetyl group of each molecule of acetyl-CoA is converted into two molecules of ________.

A)carbon dioxide
B)oxygen
C)acetone
D)acetaldehyde
E)ethanol

Question 72

Give the product(s)for the following reaction.

Question 73

In the citric acid cycle, FAD oxidizes succinate to ________.

Question 74

Each round of the citric acid cycle forms ________ molecule(s)of FADH₂.

A)1
B)0
C)3
D)2
E)4

Question 75

Give the product(s)for the following reaction.

A)
B)CH₃CH₂CH₂OH
C)CH₃CH₂OH
D)
E)

Question 76

In the second stage of the catabolism of phenylalanine, what two compounds are produced to enter the citric acid cycle?

Question 77

Identify the second step of the citric acid cycle.

A)Citrate is converted to isocitrate.
B)Conjugate addition of water to the double bond of fumarate forms (S)-malate.
C)Acetyl-CoA reacts with oxaloacetate to form citrate.
D)FAD oxidizes succinate to fumarate.
E)The secondary alcohol of isocitrate is oxidized to a ketone by NAD⁺ and the ketone loses CO₂.

Question 78

For each molecule of NADH that undergoes oxidative phosphorylation, ________ molecule(s)of ATP is (are)formed.

A)3
B)0
C)1
D)2
E)4

Question 79

Fumarate is an intermediate in the citric acid cycle. Draw its structure.

Question 80

a-Ketoglutarate is an intermediate in the citric acid cycle. Draw its structure.