Deck 22: Carbohydrate Metabolism

Question 1

Circle the carbon atoms in the molecule of glucose shown that enter the citric acid cycle as -CH₃ groups.

Answer 1

Question 2

Thiamin diphosphate (TPP)is a coenzyme

A)frequently encountered in oxidation-reduction reactions
B)required for the phosphorylation of ADP
C)involved in transfers of two-carbon groups
D)involved in transfers of one-carbon groups

Answer 2

involved in transfers of two-carbon groups

Question 3

Which of the following types of reactions are involved in glycolysis? Select all that apply.

A)nucleophilic acyl substitution
B)oxdation
C)aldol
D)reduction
E)hydrolysis
F)isomerization

Answer 3

nucleophilic acyl substitution
oxdation
aldol
isomerization

Question 4

In the course of the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate

A)an alcohol group is phosphorylated
B)an alcohol is oxidized to an aldehyde
C)an alcohol is oxidized to a carboxylic acid
D)an aldehyde is oxidized to a carboxylic acid

Question 5

In humans,what aspect(s)are the mechanism of glycosidase hydrolysis of starch by inversion and retention of stereochemistry similar?

A)formation of an oxomium ion intermediate
B)involve two inversions
C)S_N2-like inversion
D)occurs only in the small intestine
E)all of these

Question 6

Which enzyme is used in gluconeogenesis,but NOT in glycolysis?

A)PEP carboxykinase
B)enolase
C)phosphohexose isomerase
D)3-phosphoglycerate dehydrogenase

Question 7

The reaction of fructose 1,6-bisphosphate to give glyceraldehyde-3-phosphate and dihydroxyacetone phosphate is an example of

A)a reverse aldol condensation
B)hydrolysis
C)oxidation
D)dehydration

Question 8

The order of compounds in the conversion of glucose to pyruvic acid is as follows: (PEP = phosphoenolpyruvate)

A)Fructose-bisphosphate,fructose-6-phosphate,1,3-phosphoglyceric acid,3-phosphoglyceric acid,PEP.
B)Fructose-6-phosphate,fructose-bisphosphate,PEP,1,3-phosphoglyceric acid,3-phosphoglyceric acid.
C)Fructose-6-phosphate,fructose-bisphosphate,1,3-phosphoglyceric acid,3-phosphoglyceric acid,PEP.
D)Fructose-6-phosphate,fructose-bisphosphate,3-phosphoglyceric acid,1,3-phosphoglyceric acid,PEP.
E)Fructose-bisphosphate,fructose-6-phosphate,3-phosphoglyceric acid,1,3-phosphoglyceric acid,PEP.

Question 9

Which enzyme catalyzes a reaction that is a major control point for glycolysis?

A)Glyceraldehyde-3-phosphate dehydrogenase
B)Enolase
C)Phosphofructokinase
D)Aldolase

Question 10

Consider the structure of amylopectin below to answer the following questions.

a) Circle the glycosidic links that are hydrolyzed in the small intestine.
b) What is the final product of complete hydrolysis of amylpectin?

Question 11

Gluconeogenesis differs from glycolysis because

A)it does not produce ATP
B)different enzymes are involved
C)biotin is required for gluconeogenesis and not for glycolysis
D)all of these

Question 12

At the beginning of polysaccharide catabolism,a-amylase catalyzes:

A)internal (1®6)links
B)internal (1®4)links
C)terminal (1®6)links
D)terminal (1®4)links
E)all of these

Question 13

Biotin is important in gluconeogenesis for all of these reasons,except:

A)It is necessary to add CO₂ to certain intermediates in this pathway.
B)CO₂ becomes one or more of the 6 carbons in the glucose product.
C)Biotin is capable of binding covalently to CO₂.
D)Biotin helps synthesize an important precursor of phosphoenolpyruvate.
E)All of these reactions require the vitamin coenzyme.

Question 14

In the reaction catalyzed by aldolase,the substrate is bound to the enzyme

A)by an ester linkage
B)as a Schiff base
C)by a peptide bond
D)by hydrogen bonds

Question 15

Which enzyme catalyzes the reaction shown?

A)an epimerase
B)an isomerase
C)a mutase
D)a dehydrogenase

Question 16

Consider the following reaction.
Which of the following describes this reaction?

A)is so strongly exergonic that it does not require a catalyst
B)is an exergonic reaction not coupled to any other reaction
C)is an endergonic reaction that takes place because it is coupled to the exergonic hydrolysis of ATP
D)is an exergonic reaction that is coupled to the endergonic hydrolysis of ATP

Question 17

Consider the following reversible reaction.
This reaction:

A)is catalyzed by the enzyme triose phosphate isomerase
B)requires several enzymes
C)requires coenzyme A
D)requires thiamine pyrophosphate

Question 18

Consider the glycolytic intermediate below to answer the following questions.
a) What is the name of the glycolytic intermediate?”
a.1-phosphoglycerate
b. glyceraldehyde-3-phosphate
c. dibydraryacetone phosphate
d. 1,3-bisphosphoglycerate

b) Draw the sucture of the product of the reaction of this intermediate with ADP

Question 19

During the complete catabolism of a molecule of glucose,the ultimate fate of the carbon atoms are

A)pyruvate
B)AcetylCoA
C)carbon dioxide
D)fructose-6-phosphate
E)a,b or c

Question 20

Which group of small molecules best fit the boxes associated with the reaction shown?
A b c

A)ATP ADP H₂O
B)NADH NAD⁺ P_i
C)NAD⁺ NADH H₂O
D)NAD⁺ NADH P_i

Question 21

Which of the reactions of the citric acid cycle requires FAD as a coenzyme?

A)the conversion of isocitrate to a-ketoglutarate
B)the conversion of a-ketoglutarate to succinyl-CoA
C)the conversion of succinate to fumarate
D)the conversion of malate to oxaloacetate

Question 22

If gluconeogenesis were the exact reverse of glycolysis,which of the following would not be possible?

A)production and breakdown of glucose involving simpler precursors
B)formation of phosphorylated intermediates in both anabolism and catabolism of glucose
C)endergonic anabolism and catabolism of glucose
D)independent control of the anabolism and catabolism of glucose
E)c and d

Question 23

Which group of small molecules best fit the boxes associated with the reaction shown?
A b

A)ADP + 2 P_i ATP
B)NAD⁺ NADH
C)NADP⁺ NADPH
D)FAD FADH₂

Question 24

Instructions: Consider the reaction below to answer the following question(s).
Refer to instructions.This reaction:

A)is catalyzed by an oxidase.
B)involves a ring opening
C)requires ATP
D)occurs in the citric acid cycle

Question 25

Draw the structure of the ultimate organic glycolysis product of a-glucose.

Question 26

When acetyl-CoA reacts with oxaloacetate to form citrate

A)a new carbon-carbon bond is formed
B)an oxidative decarboxylation reaction takes place
C)a dehydration reaction takes place
D)a rearrangement takes place

Question 27

Which of the following are not involved in both glycolysis and gluconeogenesis?

A)pyruvate
B)oxaloacetate
C)glucose-6-phosphate
D)fructose-6-phosphate
E)all of these

Question 28

The citric acid cycle is considered to be the central metabolic pathway for all the following reasons,except:

A)It is involved in the metabolism of sugars and amino acids.
B)It is involved in the metabolism of amino acids and lipids.
C)It links anaerobic metabolism to aerobic metabolism.
D)Many of its intermediates are starting points for synthesis of a variety of compounds.
E)All of these are reasons why the citric acid cycle is considered to be the central pathway.

Question 29

Draw and name the major product of the reaction of a-glucose with ATP.

Question 30

The enzyme pyruvate carboxylase

A)is not subject to allosteric control
B)requires biotin for activity
C)catalyzes a reaction that does not require ATP
D)is inhibited by acetyl-CoA

Question 31

Which group of small molecules best fit the boxes associated with the reaction shown?
A b

A)GDP GTP
B)NADP⁺ NADPH
C)ADP + P_i ATP
D)FAD FADH₂

Question 32

The following reactions all occur during oxidative decarboxylation of pyruvate,except:

A)Removal of CO₂.
B)Oxidation of an acetate group.
C)Addition of Coenzyme A to a 2-carbon fragment.
D)Reduction of NAD⁺
E)All of these reactions take place during oxidative decarboxylation.

Question 33

Which enzymes in the citric acid cycle catalyze oxidative decarboxylation reactions?

A)isocitrate dehydrogenase and the a-ketoglutarate dehydrogenase complex
B)aconitase and succinate dehydrogenase
C)the a-ketoglutarate dehydrogenase complex and succinate thiokinase
D)fumarase and succinate dehydrogenase

Question 34

Which enzyme catalyzes the reaction shown?

A)isocitrate dehydrogenase
B)malate dehydrogenase
C)fumarase
D)succinate dehydrogenase

Question 35

The order of compounds and intermediates found in the citric acid cycle is as follows:

A)Iso-Citrate ® Aconitate ® a-Ketoglutarate ® Fumarate ® Malate ® Oxaloacetate
B)Aconitate ® iso-Citrate ® Oxaloacetate ® a-Ketoglutarate ® Malate ® Fumarate
C)Aconitate ® iso-Citrate ® a-Ketoglutarate ® Fumarate ® Malate ® Oxaloacetate
D)Aconitate ® iso-Citrate ® a-Ketoglutarate ® Malate ® Fumarate ® Oxaloacetate
E)Iso-Citrate ® Aconitate ® a-Ketoglutarate ® Malate ® Oxaloacetate ® Fumarate

Question 36

Which group of small molecules best fit the boxes associated with the reaction shown?
A b

A)ADP + 2 P_i ATP
B)NAD⁺ NADH
C)ATP ADP + 2 P_i
D)FAD FADH₂

Question 37

Instructions: Match a term or structure from the list below to each of the following definitions or names.

Question 38

The first reaction of gluconeogenesis is
This reaction is classified as:

A)an oxidative decarboxylation
B)a carboxylation
C)a redox reaction
D)a phosphate transfer

Question 39

The citric acid cycle is linked to the electron transport chain via:

A)NADH
B)FAD⁺
C)O₂
D)all of these
E)a and b

Question 40

Instructions: Consider the reaction below to answer the following question(s).


Refer to instructions.This reaction proceeds through a common enol structure.Draw the structure of the glucose/fructose enol.

Question 41

Glyceraldehyde-3-phosphate reacts with the SH group of a cysteine residue (abbreviated (Enz-SH))of a dehydrogenase to produce a hemithioaectal intermediate.Draw its structure.