Deck 21: The Organic Chemistry of Metabolism

Question 1

Which describes Step 4 of glycolysis, the cleavage of fructose 1,6-bisphosphate to two trioses?

A) Claisen condensation
B) aldol addition reaction
C) reverse-Claisen condensation
D) reverse-Aldol reaction

Answer 1

reverse-Aldol reaction

Question 2

Which reagents are necessary in the glycolysis of glucose to pyruvate?
I. NAD⁺
II. ADP
III. HPO₄^2-
IV. FAD
V. ATP

A) I, II, III, V
B) II, III, IV, V
C) I, III, V
D) III, IV, V

Answer 2

I, II, III, V

Question 3

Which describes the effect of lactate fermentation of glucose on blood pH and CO₂ concentration?

A) pH increases, CO₂ concentration increases
B) pH decreases, CO₂ concentration is unchanged
C) pH is unchanged, CO₂ concentration decreases
D) pH decreases, CO₂ concentration decreases

Answer 3

pH decreases, CO₂ concentration is unchanged

Question 4

Which is the oxidizing agent for the following reaction?

A) FAD
B) FADH₂
C) NAD⁺
D) NADH

Question 5

If deuterium is substituted for hydrogen in NADH, where will the deuterium be in the final product of the metabolic reduction of pyruvate to lactate?

A) I
B) II
C) III
D) II, III

Question 6

Which are agents for energy storage and transport?
I. ATP
II. ADP
III. NAD⁺ / NADH
IV. FAD / FADH₂

A) I, II
B) III, IV
C) I, III
D) II, IV

Question 7

How many moles of ethanol and CO₂ are produced in the glycolysis and fermentation of sucrose?

A) 2 moles ethanol, 2 moles CO₂
B) 2 moles ethanol, 4 moles CO₂
C) 4 moles ethanol, 2 moles CO₂
D) 4 moles ethanol, 4 moles CO₂

Question 8

Which is the oxidizing agent for the following reaction?

A) FAD
B) FADH₂
C) NAD⁺
D) NADH

Question 9

How many steps are there in the fatty acid $\beta$ -oxidation pathway?

A) 4
B) 6
C) 8
D) 10

Question 10

The following are key steps in fatty acid metabolism. What is the best description for the first step (A)?

A) oxidation
B) hydration
C) reverse-Claisen condensation
D) selective reduction

Question 11

If carbon atom 3 of glucose is labeled with ¹³C, which carbon atom is labeled after oxidation to pyruvate?

A) carbon atom 1
B) carbon atom 2
C) carbon atom 3
D) carbon atoms 1 and 2

Question 12

The following are key steps in fatty acid metabolism. What is the best description for the second step (B)?

A) oxidation
B) hydration
C) reverse-Claisen condensation
D) selective reduction

Question 13

Which is reagent X and product Y in this reaction?

A) X= acetyl CoA, Y= coenzyme A
B) X=coenzyme A, Y= acetyl CoA
C) X= FAD, Y= FADH₂
D) X= NAD+, Y= NADH

Question 14

If carbon 2 of glucose is labeled with ¹³C, which carbon is labeled in the alcohol fermentation products?

A) CO₂
B) ethanol carbon 1
C) ethanol carbon 2
D) ethanol carbon 1 and carbon 2

Question 15

Which statement is true concerning the balanced half reaction for the oxidation of glucose to pyruvate?

A) The reaction produces two moles of oxygen.
B) The reaction is a four-electron oxidation.
C) The reaction uses two moles of NAD+.
D) The reaction uses two moles of FAD

Question 16

The following are key steps in fatty acid metabolism. What is the best description for the third step (C)?

A) oxidation
B) hydration
C) reverse-Claisen condensation
D) selective reduction

Question 17

Which statements about carbohydrate digestion and absorption are true?
I. The main function of carbohydrates is as a carbon source.
II. Hydrolysis begins in the mouth with $\alpha$ -amylase in saliva.
III. Starch is hydrolyzed directly to glucose.
IV. Hydrolysis is completed in the small intestine.

A) I, III
B) II, IV
C) I, IV
D) II, III

Question 18

Which is the key intermediate in the enzyme catalyzed reverse-aldol reaction of fructose 1,6-bisphosphate to two trioses?

A) an amine
B) an aldehyde
C) an imine
D) an amide

Question 19

How many steps are there in the glycolysis pathway?

A) 4
B) 6
C) 8
D) 10

Question 20

Which reactions are involved in the conversion of pyruvate to ethanol?
I. oxidation
II. reduction
III. decarboxylation
IV. keto-enol tautomerization

A) I, III
B) II, IV
C) II, III
D) III, IV

Question 21

Which agent initially activates fatty acids for further reaction?

A) NAD⁺
B) FAD
C) Coenzyme A + ATP
D) ADP

Question 22

If palmitic acid is labeled at carbon 2 with ¹³C, which carbon will be labeled in acetyl-CoA after $\beta$ -oxidation?

A) the methyl carbon
B) the carbonyl carbon
C) both carbons
D) neither carbon

Question 23

Which of the following structures represents coenzyme Q?

A) I
B) II
C) III
D) IV

Question 24

What could a patient suffering from ketoacidosis do in the absence of any carbohydrate source?
I. Eat proteins: aminoacids (e.g. glutamic acid and aspartic acid) are coupled to the citric acid cycle via transamination reactions.
II. Eat fats: Acetyl-CoA from the fatty acid metabolism can be integrated in the citric acid cycle

A) I
B) II
C) both I and II

Question 25

Provide the product of the following reaction.

Question 26

Provide the product of the following reaction.

Question 27

Which best describes this reaction?

A) reverse aldol reaction
B) aldol reaction
C) reverse-Claisen condensation
D) Claisen condensation

Question 28

Which of the following structures represents coenzyme A?

A) I
B) II
C) III
D) IV

Question 29

Which statements describing $\beta$ -oxidation of fatty acid are true?
I. More energy is released in the oxidation of fatty acids than sugars.
II. Only NAD⁺ / NADH are involved in the reactions.
III. The series of four reactions is repeated until the entire fatty acid chain is degraded to acetyl-
CoA)
IV. The activated fatty acid is a carboxylic-diphosphoric mixed anhydride.

A) II, IV
B) I, III
C) II, III
D) I, IV

Question 30

Complete the structure of nicotinamide adenine dinucleotide (NAD).

Question 31

Complete the following reaction mechanism by providing the correct mechanism arrows.

Question 32

Provide the products of the following reaction.

Question 33

Provide the product of the following reaction.

Question 34

Which are oxidation / reduction reagents in the metabolism of fatty acids?
I. ATP
II. ADP
III. NAD⁺ / NADH
IV. FAD / FADH₂

A) I, II
B) III, IV
C) I, III
D) II, IV

Question 35

Provide the product of the following reaction.

Question 36

In the absence of oxaloacetate in the mitochondria . Beside a severe acidification of the body, acetoacetic acid can undergo spontaneous decarboxylation to form what aliphatic compound, which is quite toxic?

A) 2-butanone
B) 2-propanone (acetone)
C) 1-butanone
D) acetic acid

Question 37

The biosynthesis of butanoic acid proceeds via a Claisen reaction of Acetyl-CoA. If the starting material is labeled at the methyl carbon atom, which atoms will be labeled in the product?

A) I, II
B) I, III
C) II, III
D) II, IV

Question 38

Provide the product of the following reaction.

Question 39

Unsaturated fatty acids require an additional enzyme in the metabolic pathway. Which process involves this enzyme?

A) oxidation
B) reduction
C) enol / keto isomerization
D) cis / trans isomerization

Question 40

Which of the following structures represents GTP?

A) I
B) II
C) III
D) IV

Question 41

Succinic dehydrogenase catalyzes the synthesis of fumarate from succinate under simultaneous reduction of coenzyme Q. Draw the structure of fumarate in the box.

Question 42

Oxidation of D-isocitrate and simultaneous reduction of NAD⁺ to NADH and H⁺, followed by subsequent decarboxylation, leads to $\alpha$ -ketoglutarate. Complete the reaction scheme.

Question 43

The fumarase-catalyzed addition of water to fumarate leads to L-malate. Draw the structure of L-malate in the
box.

Question 44

Water-addition to cis-aconitate leads to D-isocitrate. Complete the reaction scheme.

Question 45

Provide the product of the following reaction.

Question 46

Pyruvate is the conjugate base of a $\beta$ -keto carboxylic acid.

Question 47

The following reaction is a reduction of the alcohol, oxidation of NAD⁺.

Question 48

Oxidation of L-malate by NAD⁺ catalyzed by malate dehydrogenase reduces NAD⁺ to NADH⁺ + H⁺ and transforms malate into oxaloacetate. Complete the reaction scheme and begin the next cycle

Question 49

The second reaction of the Citric Acid cycle is the water-elimination from citrate. Complete the reaction scheme.

Question 50

Transamination (amino-group transfer) of L-glutamic acid provides a link between the metabolism of sugars and amino acids. Complete the reaction scheme.

Question 51

FAD is reduced in the following reaction.

Question 52

The following structure is ADP.

Question 53

Provide the product of the following reaction.

Question 54

Acetyl-CoA is derived from the degradation of food.

Question 55

Transamination (amino-group transfer) of L-asparaginic acid provides a link between the metabolism of sugars and amino acids. Complete the reaction scheme.

Question 56

$\alpha$ -Ketoglutarate reacts under simultaneous decarboxylation and NAD⁺ - reduction to NADH and H⁺, followed by GTP-formation (guanosine-triphosphate, an ATP-analog) from GDP and phosphate, to succinate. Complete the reaction scheme.

Question 57

The cleavage of fructose-1,6-bisphosphate to two triose phosphates (reaction 4 of the glycolysis sequence) is an example of an aldol reaction.

Question 58

The Citric Acid Cycle starts with the aldol-type of reaction of acetyl-CoA with oxaloacetate. Complete the reaction scheme

Question 59

The following structure is FAD.

Question 60

Cleavage of the $\beta$ -ketoacyl-CoA in reaction 4 of the $\beta$ -oxidation of fatty acids is an example of a reverse Claisen condensation.

Question 61

The Citric acid cycle is the main metabolic pathway under anaerobic conditions.

Question 62

The Citric acid cycle oxidizes acetyl-CoA to CO₂, producing NADH and FADH₂.