Question 1

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

Accepted Answer

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 C

Question 2

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

Accepted Answer

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

Question 3

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 _________.

Accepted Answer

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 A

Question 4

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

Accepted Answer

The answer of Provide the missing names or structures for...

Question 5

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

Accepted Answer

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

Question 6

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

Accepted Answer

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

Question 7

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 ________.

Accepted Answer

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

Question 8

Fill in the missing two intermediates of glycolysis:

Accepted Answer

The answer of Fill in the missing two intermediates of...

Question 9

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

Accepted Answer

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

Question 10

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

Accepted Answer

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 11

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

Accepted Answer

The answer of For the interconversion of an aldose and...

Question 12

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

Accepted Answer

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

Question 13

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

Accepted Answer

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 14

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

Accepted Answer

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

Question 15

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?

Accepted Answer

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 16

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

Accepted Answer

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 17

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?

Accepted Answer

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

Question 18

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

Accepted Answer

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 19

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

Accepted Answer

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

Question 20

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

Accepted Answer

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

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