Question 1

The Cori cycle

Accepted Answer

A)  transports pyruvate from working muscles to the liver, where it is converted back to glucose. 
B)  is important in organisms respiring aerobically. 
C)  involves the conversion of muscle pyruvate to alanine followed by transport to the liver. 
D)  relies on functioning lactate dehydrogenase in both muscle and liver tissues. 
A)  transports pyruvate from working muscles to the liver, where it is converted back to glucose. 
B)  is important in organisms respiring aerobically. 
C)  involves the conversion of muscle pyruvate to alanine followed by transport to the liver. 
D)  relies on functioning lactate dehydrogenase in both muscle and liver tissues.

Question 2

List the three enzymes in glycolysis that are bypassed in gluconeogenesis and match them with the enzymes in gluconeogenesis that replace them.

Accepted Answer

(1) Hexokinase is replaced by glucose-1-

Question 3

Give the overall balanced reaction for the gluconeogenesis pathway, beginning from pyruvate. Please include any energy currency molecules required by the pathway.

Accepted Answer

2 pyruvate + 2NADH + 4ATP + 2

Question 4

How many of the 10 glycolysis reactions use the same enzyme in the gluconeogenesis pathway?

Accepted Answer

A)  10 
B)  7 
C)  5 
D)  3 
A)  10 
B)  7 
C)  5 
D)  3

Question 5

What molecule activates the pentose phosphate pathway?

Accepted Answer

A)  NADP+ 
B)  ribulose-5-phosphate 
C)  ADP 
D)  NADH 
A)  NADP+ 
B)  ribulose-5-phosphate 
C)  ADP 
D)  NADH

Question 6

The glycogen phosphorylase enzyme

Accepted Answer

A)  makes $\alpha$(1,4) links at the nonreducing end of glycogen. 
B)  uses Pi (phosphate) as a nucleophile in the cleavage of glucose units off of the glycogen chain. 
C)  cleaves the $\alpha$(1,6) linkages of glucose units in the glycogen polymer. 
D)  releases free glucose units as its immediate product. 
A)  makes $\alpha$(1,4) links at the nonreducing end of glycogen. 
B)  uses Pi (phosphate) as a nucleophile in the cleavage of glucose units off of the glycogen chain. 
C)  cleaves the $\alpha$(1,6) linkages of glucose units in the glycogen polymer. 
D)  releases free glucose units as its immediate product.

Question 7

Which molecule allosterically activates pyruvate carboxylase?

Accepted Answer

A)  AMP 
B)  NAD+ 
C)  epinephrine 
D)  acetyl-CoA 
A)  AMP 
B)  NAD+ 
C)  epinephrine 
D)  acetyl-CoA

Question 8

The products of the oxidative portion of the pentose phosphate pathway are carbon dioxide and

Accepted Answer

A)  2 NADH + 1 hexose phosphate. 
B)  2 NADP+ + 1 pentose phosphate. 
C)  2 NADPH + 1 hexose phosphate. 
D)  2 NADPH + 1 pentose phosphate. 
A)  2 NADH + 1 hexose phosphate. 
B)  2 NADP+ + 1 pentose phosphate. 
C)  2 NADPH + 1 hexose phosphate. 
D)  2 NADPH + 1 pentose phosphate.

Question 9

Cori disease arises from a deficient debranching enzyme. Describe the consequences for glycogen metabolism.

Accepted Answer

Individuals with Cori disease

Question 10

How would individuals with decreased levels of the pentose phosphate enzyme glucose-6-phosphate dehydrogenase respond to oxidative stress?

Accepted Answer

A)  Higher than normal levels of NADPH would accumulate. 
B)  They would not have the ability to regenerate reduced glutathione as rapidly. 
C)  They would rapidly neutralize cellular levels of H2O2 and other reactive oxygen species. 
D)  They would compensate with higher than normal levels of pentose phosphate pathway activity. 
A)  Higher than normal levels of NADPH would accumulate. 
B)  They would not have the ability to regenerate reduced glutathione as rapidly. 
C)  They would rapidly neutralize cellular levels of H2O2 and other reactive oxygen species. 
D)  They would compensate with higher than normal levels of pentose phosphate pathway activity.

Question 11

Which statement of the debranching enzyme is true?

Accepted Answer

A)  It catalyzes the addition of free glucose to a nonreducing end of glycogen. 
B)  Its product is glucose-1-phosphate. 
C)  It evenly distributes branch points across the glycogen polymer. 
D)  It is one enzyme with three unique catalytic activities. 
A)  It catalyzes the addition of free glucose to a nonreducing end of glycogen. 
B)  Its product is glucose-1-phosphate. 
C)  It evenly distributes branch points across the glycogen polymer. 
D)  It is one enzyme with three unique catalytic activities.

Question 12

Name the enzymes of the gluconeogenesis pathway that are required to form the unstable phosphoenolpyruvate molecule from pyruvate starting material.

Accepted Answer

Pyruvate carboxylase

Question 13

What are the three main sources of carbon in animals making glucose with the gluconeogenesis pathway?

Accepted Answer

(1) Glycerol from fats, (2) la

Question 14

Which hormone slows down glycolysis while stimulating gluconeogenesis through the phosphorylation of phosphofructokinase 2 (PFK2) and fructose-2,6-bisphosphatase?

Accepted Answer

A)  insulin 
B)  protein kinase 
C)  ATP 
D)  glucagon 
A)  insulin 
B)  protein kinase 
C)  ATP 
D)  glucagon

Question 15

Explain how the Cori cycle leads to the regeneration of NAD+ for muscles with an active glycolysis pathway.

Accepted Answer

After glycolysis and the formation of py

Question 16

In the reaction catalyzed by pyruvate carboxylase (the first reaction in gluconeogenesis), CO2 is

Accepted Answer

A)  lost from oxaloacetate. 
B)  activated by ATP energy. 
C)  activated by the cofactor NADH. 
D)  added to the phosphoenolpyruvate product. 
A)  lost from oxaloacetate. 
B)  activated by ATP energy. 
C)  activated by the cofactor NADH. 
D)  added to the phosphoenolpyruvate product.

Question 17

The first two reactions of gluconeogenesis are required to reverse reaction 10 (or the last reaction) of glycolysis. How many ATP equivalents are used by these first two reactions of gluconeogenesis?

Accepted Answer

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

Question 18

Two moles of pyruvate molecules running through the gluconeogenesis pathway to give 1 mole of glucose requires the hydrolysis of moles of ATP equivalents.

Accepted Answer

A)  0 
B)  2 
C)  4 
D)  6 
A)  0 
B)  2 
C)  4 
D)  6

Question 19

What triggers the Cori cycle?

Accepted Answer

A)  a buildup of cellular NAD+ 
B)  oxygen-limited working muscle cells 
C)  low levels of glucose in the muscle cells 
D)  elevated glucagon levels 
A)  a buildup of cellular NAD+ 
B)  oxygen-limited working muscle cells 
C)  low levels of glucose in the muscle cells 
D)  elevated glucagon levels

Question 20

What is the name of the enzyme that removes phosphate groups from the regulated glycogen metabolism enzymes to reverse their activity?

Accepted Answer

A)  phosphorylase kinase 
B)  protein phosphatase 1 
C)  insulin 
D)  protein kinase A 
A)  phosphorylase kinase 
B)  protein phosphatase 1 
C)  insulin 
D)  protein kinase A

Exam 14: Carbohydrate Metabolism

The Cori cycle

List the three enzymes in glycolysis that are bypassed in gluconeogenesis and match them with the enzymes in gluconeogenesis that replace them.

Give the overall balanced reaction for the gluconeogenesis pathway, beginning from pyruvate. Please include any energy currency molecules required by the pathway.

How many of the 10 glycolysis reactions use the same enzyme in the gluconeogenesis pathway?

What molecule activates the pentose phosphate pathway?

The glycogen phosphorylase enzyme

Which molecule allosterically activates pyruvate carboxylase?

The products of the oxidative portion of the pentose phosphate pathway are carbon dioxide and

Cori disease arises from a deficient debranching enzyme. Describe the consequences for glycogen metabolism.

How would individuals with decreased levels of the pentose phosphate enzyme glucose-6-phosphate dehydrogenase respond to oxidative stress?

Which statement of the debranching enzyme is true?

Name the enzymes of the gluconeogenesis pathway that are required to form the unstable phosphoenolpyruvate molecule from pyruvate starting material.

What are the three main sources of carbon in animals making glucose with the gluconeogenesis pathway?

Which hormone slows down glycolysis while stimulating gluconeogenesis through the phosphorylation of phosphofructokinase 2 (PFK2) and fructose-2,6-bisphosphatase?

Explain how the Cori cycle leads to the regeneration of NAD+ for muscles with an active glycolysis pathway.

In the reaction catalyzed by pyruvate carboxylase (the first reaction in gluconeogenesis), CO2 is

The first two reactions of gluconeogenesis are required to reverse reaction 10 (or the last reaction) of glycolysis. How many ATP equivalents are used by these first two reactions of gluconeogenesis?

Two moles of pyruvate molecules running through the gluconeogenesis pathway to give 1 mole of glucose requires the hydrolysis of moles of ATP equivalents.

What triggers the Cori cycle?

What is the name of the enzyme that removes phosphate groups from the regulated glycogen metabolism enzymes to reverse their activity?

Principles of Biochemistry

Physical Biochemistry: Energy Conversion, Water, and Membranes

Nucleic Acid Structure and Function

Protein Structure

Methods in Protein Biochemistry

Protein Function

Enzyme Mechanisms

Cell Signaling Systems

Glycolysis: a Paradigm of Metabolic Regulation

The Citrate Cycle

Oxidative Phosphorylation

Photosynthesis

Carbohydrate Structure and Function

Lipid Structure and Function

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Metabolic Integration

DNA Replication, Repair, and Recombination

RNA Synthesis, Processing, and Gene Silencing

Protein Synthesis, Posttranslational Modification, and Transport

Gene Regulation

Filters

Explain how the Cori cycle leads to the regeneration of NAD⁺for muscles with an active glycolysis pathway.

In the reaction catalyzed by pyruvate carboxylase (the first reaction in gluconeogenesis), CO₂ is