Deck 24: The Organic Chemistry of the Metabolic Pathways

Question 1

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

Answer 1

The negative charge on ATP is reduced by interactions with Mg²⁺ or positively charged side chains like those of Lys or Arg.With the negative charge reduced,nucleophiles (like water)can readily approach and attack the complexed ATP.

Question 2

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

Answer 2

Pyrophosphate is subsequently and irreversibly hydrolyzed to two equivalents of phosphate.

Question 3

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

Answer 3

an acyl phosphate and ADP

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

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

Question 6

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

Question 7

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

Question 8

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

Question 9

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 10

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 11

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

Question 12

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 13

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

Question 14

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 15

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

Question 16

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

Question 17

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

Question 18

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

Question 19

A phosphoanhydride bond is known as a ________ bond.

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

Question 20

Among those listed below,identify all the phosphoryl transfer reactions.You may choose more than one answer.

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 21

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 22

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 23

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

Question 24

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

Question 25

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

Question 26

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

Question 27

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 28

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 29

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 30

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 31

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

Question 32

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

Question 33

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

Question 34

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

Question 35

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 36

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 37

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

Question 38

________ 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 39

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 40

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 41

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 42

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

Question 43

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

Question 44

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

Question 45

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

Question 46

Draw the structure of pyruvate.

Question 47

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 48

Give the product(s)formed from the hydrolysis of a fat.You may choose more than one answer.

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

Question 49

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 50

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 51

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 52

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

Question 53

Give the product for the following reaction.

A)
B)
C)
D)
E)

Question 54

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

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

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

Question 57

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

Question 58

Draw the structure of a fatty acyl-CoA.

Question 59

Give the product(s)for the following reaction.

A)
B)CH₃CH₂CH₂OH
C)CH₃CH₂OH
D)
E)

Question 60

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 61

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

Question 62

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 63

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

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

Question 64

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 65

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 66

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

Question 67

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

Question 68

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 69

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 70

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 71

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 72

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 73

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 74

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

Question 75

Give the product(s)for the following reaction.

Question 76

Give the product(s)for the following reaction.

A)
B)CH₃CH₂CH₂OH
C)CH₃CH₂OH
D)
E)

Question 77

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

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

Question 78

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

Question 79

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 80

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.