Question 1

In comparison with the resting state, actively contracting human muscle tissue has a:

Accepted Answer

A)  higher concentration of ATP. 
B)  higher rate of lactate formation. 
C)  lower consumption of glucose. 
D)  lower rate of consumption of oxygen 
E)  lower ratio of NADH to NAD+. 
A)  higher concentration of ATP. 
B)  higher rate of lactate formation. 
C)  lower consumption of glucose. 
D)  lower rate of consumption of oxygen 
E)  lower ratio of NADH to NAD+.

Question 2

Why is an anaerobic fate of pyruvate necessary in skeletal muscle?

Accepted Answer

A)  It is required to maintain the reducing environment of the cytosol. 
B)  It allows for the re-oxidation of NADH to NAD+, as NAD+ is in limited supply during anaerobic conditions. 
C)  It decreases the pH of the skeletal muscle cell, thereby increasing release of oxygen from myoglobin. 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  It is required to maintain the reducing environment of the cytosol. 
B)  It allows for the re-oxidation of NADH to NAD+, as NAD+ is in limited supply during anaerobic conditions. 
C)  It decreases the pH of the skeletal muscle cell, thereby increasing release of oxygen from myoglobin. 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 3

The conversion of glucose into glucose 6-phosphate, which must occur in the breakdown of glucose, is thermodynamically unfavorable (endergonic). How do cells overcome this problem?

Accepted Answer

Cells overcome the thermodynamic challen

Question 4

Explain with words, diagrams, or structures why lactate accumulates in the blood during bursts of very vigorous exercise (such as a 100-meter dash).

Accepted Answer

During bursts of very vigorous exercise,

Question 5

Which amount of ATP and NADH identifies net production when 1 mol of DHAP is converted to 1 mol of pyruvate?

Accepted Answer

A)  2 mol of ATP and 2 mol of NADH 
B)  2 mol of ATP and 1 mol of NADH 
C)  2 mol ATP and 0 mol of NADH 
D)  1 mol ATP and 2 mol of NADH 
E)  1 mol ATP and 0 mol of NADH 
A)  2 mol of ATP and 2 mol of NADH 
B)  2 mol of ATP and 1 mol of NADH 
C)  2 mol ATP and 0 mol of NADH 
D)  1 mol ATP and 2 mol of NADH 
E)  1 mol ATP and 0 mol of NADH

Question 6

Which reaction in glycolysis produces ATP as a product?

Accepted Answer

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

Question 7

Yeast can metabolize D-mannose to ethanol and CO2. In addition to the glycolytic enzymes, the only other enzyme needed is phosphomannose isomerase, which converts mannose 6-phosphate to fructose 6-phosphate. If mannose is converted to ethanol and CO2 by the most direct pathway, which of the compounds and cofactors in this list are involved?
A. Lactate
B. Acetaldehyde
C. Acetyl-CoA
D. FAD
E. Glucose 6-phosphate
F. Fructose 1-phosphate
G. Pyruvate
H. Lipoic acid
I. Thiamine pyrophosphate
J. Dihydroxyacetone phosphate

Accepted Answer

Acetaldehyde
C: Acet

Question 8

In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?

Accepted Answer

A)  serine 
B)  threonine 
C)  tyrosine 
D)  histidine 
E)  arginine 
A)  serine 
B)  threonine 
C)  tyrosine 
D)  histidine 
E)  arginine

Question 9

Glucose, labeled with 14C in different carbon atoms, is added to a crude extract of a tissue rich in the enzymes of the pentose phosphate pathway. The most rapid production of 14CO2 will occur when the glucose is labeled in:

Accepted Answer

A)  C-1. 
B)  C-3. 
C)  C-4. 
D)  C-5. 
E)  C-6. 
A)  C-1. 
B)  C-3. 
C)  C-4. 
D)  C-5. 
E)  C-6.

Question 10

During strenuous activity, muscle tissue demands large quantities of ATP, compared with resting muscle. In white skeletal muscle (in contrast with red muscle), ATP is produced almost exclusively by fermentation of glucose to lactate. If a person had white muscle tissue devoid of the enzyme lactate dehydrogenase, how would this affect his or her metabolism at rest and during strenuous exercise?

Accepted Answer

Without the enzyme lactate dehydrogenase

Question 11

The first reaction in glycolysis that results in the formation of an energy-rich compound is catalyzed by:

Accepted Answer

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

Question 12

The pentose phosphate pathway is multifunctional with metabolic flexibility. Which statement is FALSE with respect to this pathway?

Accepted Answer

A)  All the enzymes in this pathway are located in the cytosol. 
B)  All intermediates in this pathway are phosphorylated. 
C)  The activities of transaldolases and transketolases link this pathway to gluconeogenesis. 
D)  It generates NADH for reductive biosynthesis. 
E)  In erythrocytes, this pathway is required to maintain glutathione in a reduced state. 
A)  All the enzymes in this pathway are located in the cytosol. 
B)  All intermediates in this pathway are phosphorylated. 
C)  The activities of transaldolases and transketolases link this pathway to gluconeogenesis. 
D)  It generates NADH for reductive biosynthesis. 
E)  In erythrocytes, this pathway is required to maintain glutathione in a reduced state.

Question 13

Describe the fate of pyruvate, formed by glycolysis in animal skeletal muscle, under two conditions: (a) at rest, and (b) during an all-out sprint. Show enough detail in your answer to explain why pyruvate metabolism is different in these two cases.

Accepted Answer

At rest, pyruvate formed by glycolysis i

Question 14

Briefly describe the possible metabolic fates of pyruvate produced by glycolysis in humans, and explain the circumstances that favor each.

Accepted Answer

Pyruvate, the end product of glycolysis,

Question 15

In the alcoholic fermentation of glucose by yeast, thiamine pyrophosphate is a coenzyme required by:

Accepted Answer

A)  aldolase. 
B)  hexokinase. 
C)  lactate dehydrogenase. 
D)  pyruvate decarboxylase. 
E)  transaldolase. 
A)  aldolase. 
B)  hexokinase. 
C)  lactate dehydrogenase. 
D)  pyruvate decarboxylase. 
E)  transaldolase.

Question 16

Which reaction in glycolysis requires ATP as a substrate?

Accepted Answer

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

Question 17

Two reactions in glycolysis produce ATP. For each of these, show the name and structure of reactant and product, indicate which cofactors participate and where, and name the enzymes.

Accepted Answer

The two reactions in glycolysis that pro

Question 18

In gluconeogenesis, how do animals convert pyruvate to phosphoenolpyruvate? Show structures, enzymes, and cofactors.

Accepted Answer

In gluconeogenesis, animals convert pyru

Question 19

Which compound(s) is/are a high-energy product(s) of glycolysis?

Accepted Answer

A)  fructose 1,6-bisphosphate 
B)  ATP and NADH 
C)  1,3-bisphosphoglycerate and phosphoenol pyruvate 
D)  fructose 1,6-bisphosphate, 1,3-bisphosphoglycerate, and phosphoenol pyruvate 
E)  ATP, NADH, 1,3-bisphosphoglycerate, and phosphoenol pyruvate 
A)  fructose 1,6-bisphosphate 
B)  ATP and NADH 
C)  1,3-bisphosphoglycerate and phosphoenol pyruvate 
D)  fructose 1,6-bisphosphate, 1,3-bisphosphoglycerate, and phosphoenol pyruvate 
E)  ATP, NADH, 1,3-bisphosphoglycerate, and phosphoenol pyruvate

Question 20

Which enzyme acts in the pentose phosphate pathway?

Accepted Answer

A)  6-phosphogluconate dehydrogenase 
B)  aldolase 
C)  glycogen phosphorylase 
D)  phosphofructokinase-1 
E)  pyruvate kinase 
A)  6-phosphogluconate dehydrogenase 
B)  aldolase 
C)  glycogen phosphorylase 
D)  phosphofructokinase-1 
E)  pyruvate kinase

Exam 14: Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

In comparison with the resting state, actively contracting human muscle tissue has a:

Why is an anaerobic fate of pyruvate necessary in skeletal muscle?

The conversion of glucose into glucose 6-phosphate, which must occur in the breakdown of glucose, is thermodynamically unfavorable (endergonic). How do cells overcome this problem?

Explain with words, diagrams, or structures why lactate accumulates in the blood during bursts of very vigorous exercise (such as a 100-meter dash).

Which amount of ATP and NADH identifies net production when 1 mol of DHAP is converted to 1 mol of pyruvate?

Which reaction in glycolysis produces ATP as a product?

In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?

Glucose, labeled with 14C in different carbon atoms, is added to a crude extract of a tissue rich in the enzymes of the pentose phosphate pathway. The most rapid production of 14CO2 will occur when the glucose is labeled in:

The first reaction in glycolysis that results in the formation of an energy-rich compound is catalyzed by:

The pentose phosphate pathway is multifunctional with metabolic flexibility. Which statement is FALSE with respect to this pathway?

Describe the fate of pyruvate, formed by glycolysis in animal skeletal muscle, under two conditions: (a) at rest, and (b) during an all-out sprint. Show enough detail in your answer to explain why pyruvate metabolism is different in these two cases.

Briefly describe the possible metabolic fates of pyruvate produced by glycolysis in humans, and explain the circumstances that favor each.

In the alcoholic fermentation of glucose by yeast, thiamine pyrophosphate is a coenzyme required by:

Which reaction in glycolysis requires ATP as a substrate?

Two reactions in glycolysis produce ATP. For each of these, show the name and structure of reactant and product, indicate which cofactors participate and where, and name the enzymes.

In gluconeogenesis, how do animals convert pyruvate to phosphoenolpyruvate? Show structures, enzymes, and cofactors.

Which compound(s) is/are a high-energy product(s) of glycolysis?

Which enzyme acts in the pentose phosphate pathway?

The Foundations of Biochemistry

Water

Amino Acids, Peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biological Membranes and Transport

Biosignaling

Bioenergetics and Biochemical Reaction Types

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, Nucleotides, and Related Molecules

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

Glucose, labeled with ¹⁴C in different carbon atoms, is added to a crude extract of a tissue rich in the enzymes of the pentose phosphate pathway. The most rapid production of ¹⁴CO₂ will occur when the glucose is labeled in: