Deck 13: Carbohydrate Metabolism: Glycolysis, gluconeogenesis, glycogen Metabolism, and the Pentose Phosphate Pathway

Question 1

Under conditions of strenuous exercise,gluconeogenesis occurs primarily in the _______ using _______ formed in the skeletal muscle

A)kidney;alanine
B)muscle;glycerol
C)liver;propionate
D)kidney;acetyl-CoA
E)liver;lactate

Answer 1

E

Question 2

During the energy investment phase of glycolysis,_____ reaction(s)use ATP as a substrate while during the energy generation phase,_____ reactions produce ATP as a product.

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

Answer 2

A

Question 3

Besides two molecules of pyruvate,what are the net products of glycolysis?

A)4 ATP and 2 NADH
B)2 ATP and 2 NADH
C)4 ATP and 4 NADH
D)2 ATP and 4 NADH
E)none of the above

Answer 3

B

Question 4

Which of the following enzymes is used by the gluconeogenic pathway but not the glycolytic pathway?

A)pyruvate kinase
B)phosphoenolpyruvate carboxykinase
C)glyceraldehyde-3-phosphate dehydrogenase
D)triose phosphate isomerase
E)hexokinase

Question 5

Which isoform of hexokinase is found in the vertebrate liver?

A)hexokinase I
B)hexokinase II
C)hexokinase III
D)hexokinase IV
E)all of the above

Question 6

In most bacteria that utilize glucose,what molecule both aids in transport of glucose into the cell and is phosphorylating agent for conversion of glucose to glucose-6-phosphate?

A)ATP
B)GTP
C)fructose-1,6-bisphosphate
D)1,3-bisphosphoglycerate
E)phosphoenolpyruvate

Question 7

Which enzyme catalyzes the primary regulation site of glycolysis?

A)hexokinase
B)phosphofructokinase-1
C)glyceraldehyde-3-phosphate dehydrogenase
D)phosphoglycerate kinase
E)pyruvate kinase

Question 8

Which of the following glycolytic reactions is freely reversible?

A)hexokinase
B)phosphofructokinase
C)triose phosphate isomerase
D)pyruvate kinase
E)none of the above

Question 9

During aerobic glycolysis,pyruvate is most likely oxidized to ________ while in anaerobic glycolysis,pyruvate is converted to _________.

A)acetaldehyde;ethanol
B)acetyl CoA;glyceraldehyde
C)acetyl CoA;lactate
D)acetaldehyde;lactate
E)none of the above

Question 10

The reaction catalyzed by triose phosphate isomerase is most similar in mechanism to which of the following glycolytic enzymes?

A)glucose-6-phosphate isomerase
B)fructose-1,6-bisphosphate aldolase
C)phosphoglycerate mutase
D)enolase
E)pyruvate kinase

Question 11

During the oxidation of glyceraldehyde-3-phosphate,what intermediate in the enzyme-catalyzed mechanism actually undergoes oxidation?

A)enediol
B)thioester
C)thiohemiacetal
D)carbinolamine
E)Schiff base

Question 12

The conversion of 3-phosphoglycerate to phosphoenolpyruvate requires two reactions.Which of the following correctly identifies the types of reactions in the proper order of glycolysis?

A)isomerization,hydration
B)hydration,isomerization
C)dehydration,isomerization
D)isomerization,dehydration
E)mutation,dehydration

Question 13

Conversion of pyruvate to acetaldehyde requires _______ while conversion of acetaldehyde to ethanol requires _______.

A)thiamine pyrophosphate;NAD⁺
B)pyridoxal phosphate;FADH₂
C)biotin;NADH
D)biotin;FAD
E)thiamine pyrophosphate;NADH

Question 14

Assuming that gluconeogenesis was active in a mammalian liver,under what conditions would PEPCK have more activity in the mitochondria than in the cytosol?

A)the activity of pyruvate carboxylase was very low
B)high levels of malate were being transported out of the mitochondria
C)lactate was serving as the primary carbon source for gluconeogenesis
D)glycerol was serving as the primary carbon source for gluconeogenesis
E)none of the above

Question 15

If unregulated,which of the following pairs of enzymes would represent a futile cycle?

A)pyruvate kinase and pyruvate carboxylase
B)pyruvate carboxylase and phosphoenolpyruvate carboxykinase
C)pyruvate kinase and fructose-1,6-bisphosphatase
D)fructose-1,6-bisphosphatase and phosphofructokinase
E)glucose-6-phosphatase and phosphofructokinase

Question 16

The conversion of phosphoenolpyruvate and ADP to pyruvate and ATP occurs in two distinct steps,first the transfer of the phosphate from PEP to ADP,then the conversion of enolpyruvate to pyruvate.Which of the following describes the reversibility of this process?

A)both steps are freely reversible
B)step 1 is freely reversible,step 2 is irreversible
C)step 1 is irreversible,step 2 is freely reversible
D)both steps are irreversible
E)the reversibility of the reaction depends completely upon the concentrations of products and reactants

Question 17

Which of the following is the fate of pyruvate in a blood cell?

A)acetyl CoA
B)carbon dioxide
C)lactate
D)ethanol
E)none of the above

Question 18

With respect to carbons 1 and 2 of the intermediate in the conversion of glucose-6-phosphate to fructose-6-phosphate,which of the following would best describe this intermediate?

A)vicinal diol
B)enediol
C)aldehyde
D)ketone
E)enol

Question 19

Which of the following pairs of phosphorylated molecules contains an intermediate of glycolysis with high phosphate transfer potential and one with low phosphate transfer potential?

A)fructose-1,6-bisphosphate and fructose-6-phosphate
B)phosphoenolpyruvate and glyceraldehyde-3-phosphate
C)fructose-1,6-bisphosphate and 3-phosphoglycerate
D)1,3-bisphosphoglycerate and phosphoenolpyruvate
E)1,3-bisphosphoglycerate and pyruvate

Question 20

What is the initial step in the mechanism of fructose-1,6-bisphosphate aldolase when the substrate is fructose-1,6-bisphosphate in its open-chain form?

A)attack of C-2 carbonyl group by the amine of lysine
B)deprotonation of C-3 hydroxyl by aspartate
C)protonation of C-2 carbonyl oxygen by histidine
D)attack of C-2 carbonyl group by the thiol of cysteine
E)none of the above

Question 21

When glucagon binds to receptors on mammalian liver cells,which of the following occurs due to enzyme phosphorylation?

A)activation of PFK-2 followed by activation of glycolysis
B)activation of FBPase-2 followed by inhibition of gluconeogenesis
C)activation of PFK-2 followed by activation of gluconeogenesis
D)activation of FBPase-2 followed by activation of gluconeogenesis
E)activation of PFK-2 followed by inhibition of glycolysis

Question 22

What sequence of enzymes allows for the synthesis of glycogen from glucose-6-phosphate?

A)UDP-glucose pyrophosphorylase,phosphoglucomutase,glycogen synthase,amylo-(1,4 $\to$ 1,6)-transglycosylase
B)phosphoglucomutase,UDP-glucose pyrophosphorylase,amylo-(1,4 $\to$ 1,6)-transglycosylase,glycogen synthase
C)phosphoglucomutase,amylo-(1,4 $\to$ 1,6)-transglycosylase,UDP-glucose pyrophosphorylase,glycogen synthase
D)UDP-glucose pyrophosphorylase,phosphoglucomutase,amylo-(1,4 $\to$ 1,6)-transglycosylase,glycogen synthase
E)phosphoglucomutase,UDP-glucose pyrophosphorylase,glycogen synthase,amylo-(1,4 $\to$ 1,6)-transglycosylase

Question 23

Which of the following activators is correctly paired with the glycolytic or gluconeogenic enzyme that it activates?

A)glucose-6-phosphate: hexokinase
B)AMP: fructose-1,6-bisphosphatase
C)ATP: pyruvate kinase
D)fructose-2,6-bisphosphate: phosphofructokinase
E)citrate: fructose-1,6-bisphosphatase

Question 24

The oxidative phase of the pentose phosphate pathway has _____ oxidation reactions,effectively oxidizing an ___________ to ____________.

A)2;alcohol;a carboxylic acid
B)2;aldehyde;a carboxylic acid
C)2;aldehyde;carbon dioxide
D)3;alcohol;a carboxylic acid
E)3;alcohol;carbon dioxide

Question 25

In the vertebrate liver,which major regulatory point is bypassed during fructose metabolism,often leading to conversion of excess fructose into fat?

A)hexokinase
B)phosphofructokinase
C)glyceraldehyde-3-phosphate dehydrogenase
D)pyruvate kinase
E)none of the above

Question 26

Which of the following intermediates is a feed-forward activator of pyruvate kinase?

A)glucose-6-phosphate
B)fructose-1,6-bisphosphate
C)fructose-2,6-bisphosphate
D)glyceraldehyde-3-phosphate
E)phosphoenolpyruvate

Question 27

Which of the following is correctly paired with the glycolytic intermediate that serves as its precursor?

A)ribulose-5-phosphate: fructose-6-phosphate
B)serine: phosphoenolpyruvate
C)glycogen: glucose-6-phosphate
D)glycerol-3-phosphate: glyceraldehyde-3-phosphate
E)glucosamine: fructose-1,6-bisphosphate

Question 28

Fill in the missing two intermediates of glycolysis:

Question 29

Which of the following enzymes is activated when acted on by phosphoprotein phosphatase 1?

A)glycogen synthase
B)glycogen phosphorylase
C)phosphorylase kinase
D)phosphoprotein phosphatase inhibitor 1
E)protein kinase A

Question 30

A transketolase enzyme transfers a _____ carbon fragment from a(n)________ to a(n)________.

A)2;aldose;ketose
B)2;ketose;aldose
C)2;ketose;ketose
D)3;aldose;ketose
E)3;ketose;aldose

Question 31

When lipid biosynthesis is active using carbohydrates as a source of carbon,three things are needed: NADPH,ATP and acetyl-CoA (from pyruvate).Which of the following best explains the operation of the pentose phosphate pathway (PPP)under such conditions? G6P = glucose-6-phosphate,F6P = fructose-6-phosphate,G3P = glyceraldehyde-3-phosphate

A)3 G6P $\to$ 2 F6P + 1 G3P with the F6P recycled to G6P to re-enter the PPP while G3P continues through glycolysis to make acetyl-CoA and ATP
B)6 G6P $\to$ 4 F6P + 2 G3P with 1 G3P converted to DHAP,the other G3P + DHAP giving F6P with all F6P recycled to G6P to re-enter the PPP
C)3 G6P $\to$ 2 F6P + 1 G3P with the F6P and G3P continuing through glycolysis to make acetyl-CoA and ATP
D)3 G6P $\to$ 2 F6P + 1 G3P with all G3P continuing through glycolysis.Some F6P is recycled to G6P while some continues through glycolysis-the amount dependent upon the requirements for NADPH,ATP and acetyl-CoA
E)none of the above

Question 32

In the mammalian liver,hexokinase IV is sequestered in _______ when glucose concentrations are low.When glucose concentrations are high,it is found in the cytosol bound to the enzyme ________.

A)nucleus;PFK-2
B)Golgi apparatus;PFK-2
C)endoplasmic reticulum;PFK-2
D)nucleus;PFK-1
E)Golgi apparatus;PFK-1

Question 33

When glucagon binds to its receptor on a liver cell,which of the following sequence of events occurs to activate protein kinase A?

A)activation of adenylate cyclase,activation of G protein,production of cAMP
B)activation of G protein,activation of adenylate cyclase,production of cAMP
C)activation of G protein,production of cAMP,activation of adenylate cyclase
D)production of cAMP,activation of adenylate cyclase,activation of G protein
E)none of the above

Question 34

Provide the missing names or structures for the following scheme of the fermentation of pyruvate

Question 35

The conversion of ribulose-5-phosphate to xylulose-5-phosphate requires what enzyme?

A)phosphopentose isomerase
B)phosphopentose epimerase
C)transketolase
D)transaldolase
E)lactonase

Question 36

Experiments that investigated the Pasteur effect showed that when oxygen is introduced to cells where glycolysis is occurring,all intermediates beginning with ________ become depleted due to inhibition of the enzyme _________.

A)fructose-1,6-bisphosphate;phosphofructokinase
B)glucose-6-phosphate: hexokinase
C)fructose-6-phosphate;phosphofructokinase
D)fructose-1,6-bisphosphate;fructose-1,6-bisphosphate aldolase
E)phosphoenolpyruvate;pyruvate kinase

Question 37

If a residue of glucose in glycogen is removed from the glycogen molecule and then allowed to proceed through glycolysis to pyruvate,what is the net production of ATP?

A)1
B)2
C)3
D)4
E)5

Question 38

In its non-phosphorylated state,glycogen phosphorylase can be activated by which of the following molecules?

A)ATP
B)glucose-6-phosphate
C)glucose
D)AMP
E)none of the above

Question 39

Besides its role in glycogen synthesis,which of the following directly relies on UDP-glucose?

A)glycolysis
B)gluconeogenesis
C)fructose metabolism
D)sucrose metabolism
E)galactose metabolism

Question 40

For the interconversion of an aldose and ketose,show the intermediate of the reaction.