Question 1

During fasting,what role does gluconeogenesis play?

Accepted Answer

A) Aids in the release of glucose from stored glycogen in the liver. 
B) Uses alanine to restore blood glucose levels. 
C) Produces products that slow the oxidation of pyruvate. 
D) Helps transport glucose across the blood-brain barrier to maintain brain glucose levels. 
A) Aids in the release of glucose from stored glycogen in the liver. 
B) Uses alanine to restore blood glucose levels. 
C) Produces products that slow the oxidation of pyruvate. 
D) Helps transport glucose across the blood-brain barrier to maintain brain glucose levels. B

Question 2

Glycogen phosphorylase is ________ (more,less)active when phosphorylated,and it is ________ (activated,inhibited)by glucose 6-phosphate.

Accepted Answer

A) more;activated 
B) less;activated 
C) more;inhibited 
D) less;inhibited 
A) more;activated 
B) less;activated 
C) more;inhibited 
D) less;inhibited C

Question 3

Glycogen phosphorylase was the first enzyme shown to be regulated by ________.

Accepted Answer

A) covalent modification 
B) proteolytic cleavage 
C) a cascade reaction 
D) feedback inhibition 
A) covalent modification 
B) proteolytic cleavage 
C) a cascade reaction 
D) feedback inhibition A

Question 4

The interconversion of which pair of substrates is used as a regulatory point in gluconeogenesis?

Accepted Answer

A) Lactate and pyruvate. 
B) Dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. 
C) Fructose 1,6-bisphosphate and fructose 6-phosphate. 
D) Phosphoenolpyruvate and 2-phosphoglycerate. 
A) Lactate and pyruvate. 
B) Dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. 
C) Fructose 1,6-bisphosphate and fructose 6-phosphate. 
D) Phosphoenolpyruvate and 2-phosphoglycerate.

Question 5

Gluconeogenesis is regulated by

Accepted Answer

A) glucagon. 
B) allosteric modulation. 
C) concentration of its substrates. 
D) All of the above. 
A) glucagon. 
B) allosteric modulation. 
C) concentration of its substrates. 
D) All of the above.

Question 6

Two molecules of NADPH are generated for each molecule of glucose 6-phosphate that enters the pentose phosphate pathway.

Accepted Answer

A) True 
 B)False

Question 7

Glucose 1,6-bisphosphate is the primary starting substrate for the pentose phosphate pathway.

Accepted Answer

A) True 
 B)False

Question 8

The pentose phosphate pathway has two primary products.They are ________.

Accepted Answer

A) ATP and NADPH 
B) oxaloacetate and acetyl CoA 
C) sorbitol and fructose 
D) ribose-5-phosphate and NADPH 
A) ATP and NADPH 
B) oxaloacetate and acetyl CoA 
C) sorbitol and fructose 
D) ribose-5-phosphate and NADPH

Question 9

Glycogen degradation occurs in

Accepted Answer

A) muscle. 
B) liver. 
C) muscle and liver. 
D) saliva. 
E) brain cells. 
A) muscle. 
B) liver. 
C) muscle and liver. 
D) saliva. 
E) brain cells.

Question 10

Under fasting conditions the liver increases its rate of gluconeogenesis to maintain blood glucose levels,but this can only be maintained for a few days before the rate decreases.

Accepted Answer

A) True 
 B)False

Question 11

There are no branched polysaccharide chains in limit dextrin.

Accepted Answer

A) True 
 B)False

Question 12

Gluconeogenesis uses the same enzymatic reactions of glycolysis except for the ________.

Accepted Answer

A) pyruvate kinase catalyzed step 
B) 4 irreversible reactions in glycolysis 
C) 3 irreversible reactions in glycolysis 
D) 2 irreversible reactions in glycolysis 
A) pyruvate kinase catalyzed step 
B) 4 irreversible reactions in glycolysis 
C) 3 irreversible reactions in glycolysis 
D) 2 irreversible reactions in glycolysis

Question 13

Which is evidence for gluconeogenesis being a more ancient metabolic pathway than glycolysis?

Accepted Answer

A) The protein sequences for the gluconeogenesis enzymes are less conserved than those for glycolysis,indicating greater diversity developed by evolution. 
B) Many archaebacterial enzymes for gluconeogenesis have the same catalytic triad as those in modern mammals. 
C) Glycolysis in bacteria generally has fewer pathway steps,indicating that it has had less time to evolve. 
D) Some bacterial species that diverged very early in prokaryotic evolution have gluconeogenesis,but not glycolysis. 
A) The protein sequences for the gluconeogenesis enzymes are less conserved than those for glycolysis,indicating greater diversity developed by evolution. 
B) Many archaebacterial enzymes for gluconeogenesis have the same catalytic triad as those in modern mammals. 
C) Glycolysis in bacteria generally has fewer pathway steps,indicating that it has had less time to evolve. 
D) Some bacterial species that diverged very early in prokaryotic evolution have gluconeogenesis,but not glycolysis.

Question 14

Glucose is stored as ________ in bacteria and animals.

Accepted Answer

A) glucagon 
B) starch 
C) glycogen 
D) NADPH 
A) glucagon 
B) starch 
C) glycogen 
D) NADPH

Question 15

Which is true about glycogen phosphorylase in liver and muscle?

Accepted Answer

A) They are identical and activated in the same way. 
B) In liver glucose is an inhibitor;glucose is not an inhibitor in muscle. 
C) The liver enzyme is activated by phosphorylation,but the muscle version is activated by proteolytic cleavage. 
D) Glycogen phosphorylase is found only in liver,there is none in muscle tissue. 
A) They are identical and activated in the same way. 
B) In liver glucose is an inhibitor;glucose is not an inhibitor in muscle. 
C) The liver enzyme is activated by phosphorylation,but the muscle version is activated by proteolytic cleavage. 
D) Glycogen phosphorylase is found only in liver,there is none in muscle tissue.

Question 16

During fasting,when glycogen supplies are depleted,________ become a major source of carbon for gluconeogenesis.

Accepted Answer

A) amino acids 
B) nucleic acids 
C) fatty acids 
D) lactate and pyruvate 
A) amino acids 
B) nucleic acids 
C) fatty acids 
D) lactate and pyruvate

Question 17

Binding of epinephrine to a1-adrenergic receptors has what effect?

Accepted Answer

A) Elevates the degradation rate of glycogen. 
B) Activates protein kinase A. 
C) Lowers the rate of glycogen synthesis. 
D) Reduces the effects of insulin. 
E) All of the above. 
A) Elevates the degradation rate of glycogen. 
B) Activates protein kinase A. 
C) Lowers the rate of glycogen synthesis. 
D) Reduces the effects of insulin. 
E) All of the above.

Question 18

Unlike liver tissue,muscle and some other tissues differ in regulation of glycogen metabolism because

Accepted Answer

A) the enzymes are different. 
B) there is no effect of glucagon. 
C) there is no effect of insulin. 
D) inhibitor-1 controls protein phosphatase-1. 
E) there is no role for cyclic AMP. 
A) the enzymes are different. 
B) there is no effect of glucagon. 
C) there is no effect of insulin. 
D) inhibitor-1 controls protein phosphatase-1. 
E) there is no role for cyclic AMP.

Question 19

Which is not a function of the main products of the pentose phosphate pathway?

Accepted Answer

A) To maintain levels of NADPH. 
B) To provide reducing power for the synthesis of fatty acids. 
C) To serve as precursors in the biosynthesis of RNA and DNA. 
D) To raise the concentration of cAMP. 
A) To maintain levels of NADPH. 
B) To provide reducing power for the synthesis of fatty acids. 
C) To serve as precursors in the biosynthesis of RNA and DNA. 
D) To raise the concentration of cAMP.

Question 20

In addition to control of activity by phosphorylation,phosphorylase kinase is activated by

Accepted Answer

A) Calmodulin. 
B) Ca2+. 
C) cAMP. 
D) Inhibitor-1. 
A) Calmodulin. 
B) Ca2+. 
C) cAMP. 
D) Inhibitor-1.

Exam 12: Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

During fasting,what role does gluconeogenesis play?

Glycogen phosphorylase is ________ (more,less)active when phosphorylated,and it is ________ (activated,inhibited)by glucose 6-phosphate.

Glycogen phosphorylase was the first enzyme shown to be regulated by ________.

The interconversion of which pair of substrates is used as a regulatory point in gluconeogenesis?

Gluconeogenesis is regulated by

Two molecules of NADPH are generated for each molecule of glucose 6-phosphate that enters the pentose phosphate pathway.

Glucose 1,6-bisphosphate is the primary starting substrate for the pentose phosphate pathway.

The pentose phosphate pathway has two primary products.They are ________.

Glycogen degradation occurs in

Under fasting conditions the liver increases its rate of gluconeogenesis to maintain blood glucose levels,but this can only be maintained for a few days before the rate decreases.

There are no branched polysaccharide chains in limit dextrin.

Gluconeogenesis uses the same enzymatic reactions of glycolysis except for the ________.

Which is evidence for gluconeogenesis being a more ancient metabolic pathway than glycolysis?

Glucose is stored as ________ in bacteria and animals.

Which is true about glycogen phosphorylase in liver and muscle?

During fasting,when glycogen supplies are depleted,________ become a major source of carbon for gluconeogenesis.

Binding of epinephrine to a1-adrenergic receptors has what effect?

Unlike liver tissue,muscle and some other tissues differ in regulation of glycogen metabolism because

Which is not a function of the main products of the pentose phosphate pathway?

In addition to control of activity by phosphorylation,phosphorylase kinase is activated by

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Proteins: Three-Dimensional Structure and Function

Properties of Enzymes

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Glycolysis

The Citric Acid Cycle

Electron Transport and Atp Synthesis

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

DNA Replication, repair, and Recombination

Transcription and RNA Processing

Protein Synthesis

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Glycogen phosphorylase is (more,less)active when phosphorylated,and it is (activated,inhibited)by glucose 6-phosphate.