Question 1

Which compound can be described as exclusively ketogenic?

Accepted Answer

A)  leucine 
B)  isoleucine 
C)  lysine 
D)  both leucine and lysine 
E)  both isoleucine and lysine 
A)  leucine 
B)  isoleucine 
C)  lysine 
D)  both leucine and lysine 
E)  both isoleucine and lysine

Question 2

Which amino acid is used to transport nitrogen to the liver?

Accepted Answer

A)  alanine 
B)  asparagine 
C)  glutamine 
D)  glutamate 
E)  both alanine and glutamine 
A)  alanine 
B)  asparagine 
C)  glutamine 
D)  glutamate 
E)  both alanine and glutamine

Question 3

Which compound can be described as glucogenic?

Accepted Answer

A)  leucine 
B)  isoleucine 
C)  lysine 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  leucine 
B)  isoleucine 
C)  lysine 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 4

Methionine synthase uses what substrates to synthesize methionine?

Accepted Answer

A)  cysteine 
B)  S-adenosyl methionine 
C)  ATP 
D)  homocysteine 
A)  cysteine 
B)  S-adenosyl methionine 
C)  ATP 
D)  homocysteine

Question 5

During starvation, more urea production occurs. Explain this observation.

Accepted Answer

During starvation, the body's primary so

Question 6

Which statement is TRUE regarding glutamine synthetase?

Accepted Answer

A)  This enzyme is classified as a ligase. 
B)  An intermediate in the reaction catalyzed by this enzyme is an acyl phosphate. 
C)  This enzyme catalyzes a transamination reaction. 
D)  This enzyme is classified as a ligase, and an intermediate in the reaction catalyzed by this enzyme is an acyl phosphate. 
E)  This enzyme is classified as a ligase and catalyzes a transamination reaction. 
A)  This enzyme is classified as a ligase. 
B)  An intermediate in the reaction catalyzed by this enzyme is an acyl phosphate. 
C)  This enzyme catalyzes a transamination reaction. 
D)  This enzyme is classified as a ligase, and an intermediate in the reaction catalyzed by this enzyme is an acyl phosphate. 
E)  This enzyme is classified as a ligase and catalyzes a transamination reaction.

Question 7

Outline two paths by which 14N-labeled glutamate can lead to labeled products in the urea cycle.

Accepted Answer

The N-labeled glutamate can lead to labe

Question 8

If 14C-labeled glutamate is introduced into liver cells, what compounds in the urea cycle will be rapidly labeled with the carbon?

Accepted Answer

A)  ornithine 
B)  aspartate 
C)  arginine 
D)  urea 
E)  None of the answers is correct. 
A)  ornithine 
B)  aspartate 
C)  arginine 
D)  urea 
E)  None of the answers is correct.

Question 9

In which pair of compounds is the second molecule produced by the deamination of the first molecule?

Accepted Answer

A)  aspartic acid and oxaloacetate 
B)  glutamine and glutamate 
C)  alanine and pyruvate 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  aspartic acid and oxaloacetate 
B)  glutamine and glutamate 
C)  alanine and pyruvate 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 10

What processes are associated with the glucose-alanine cycle?

Accepted Answer

A)  Gluconeogenesis in the liver 
B)  Glutamate synthesis in both muscle and the liver 
C)  Glucose export from the liver 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  Gluconeogenesis in the liver 
B)  Glutamate synthesis in both muscle and the liver 
C)  Glucose export from the liver 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 11

Which amino acid can be considered to be both glucogenic and ketogenic?

Accepted Answer

A)  threonine 
B)  aspartate 
C)  leucine 
D)  isoleucine 
E)  both threonine and isoleucine 
A)  threonine 
B)  aspartate 
C)  leucine 
D)  isoleucine 
E)  both threonine and isoleucine

Question 12

Glutamate is metabolically converted to $\alpha$-ketoglutarate and NH4+ by a process described as:

Accepted Answer

A)  deamination. 
B)  hydrolysis. 
C)  oxidative deamination. 
D)  reductive deamination. 
E)  transamination. 
A)  deamination. 
B)  hydrolysis. 
C)  oxidative deamination. 
D)  reductive deamination. 
E)  transamination.

Question 13

In the human genetic disease maple syrup urine disease, the metabolic defect involves:

Accepted Answer

A)  a deficiency of the vitamin niacin. 
B)  oxidative decarboxylation. 
C)  synthesis of branched chain amino acids. 
D)  transamination of an amino acid. 
E)  uptake of branched chain amino acids into liver. 
A)  a deficiency of the vitamin niacin. 
B)  oxidative decarboxylation. 
C)  synthesis of branched chain amino acids. 
D)  transamination of an amino acid. 
E)  uptake of branched chain amino acids into liver.

Question 14

Nitrogen from protein is eliminated as what compound in animals?

Accepted Answer

A)  ammonia 
B)  urea 
C)  pyrimidine 
D)  both ammonia and urea 
E)  both urea and pyrimidine 
A)  ammonia 
B)  urea 
C)  pyrimidine 
D)  both ammonia and urea 
E)  both urea and pyrimidine

Question 15

Which statement is TRUE regarding the conversion of arginine to ornithine in the urea cycle?

Accepted Answer

A)  The enzyme catalyzing this reaction is a hydrolase. 
B)  This enzyme-catalyzed reaction occurs in the matrix. 
C)  One of the products of this reaction is fumarate. 
D)  The enzyme catalyzing this reaction is a ligase. 
E)  The enzyme catalyzing this reaction is a hydrolase, and the reaction occurs in a matrix. 
A)  The enzyme catalyzing this reaction is a hydrolase. 
B)  This enzyme-catalyzed reaction occurs in the matrix. 
C)  One of the products of this reaction is fumarate. 
D)  The enzyme catalyzing this reaction is a ligase. 
E)  The enzyme catalyzing this reaction is a hydrolase, and the reaction occurs in a matrix.

Question 16

Define zymogen and describe the role of one zymogen in protein digestion.

Accepted Answer

Zymogen is an inactive precursor form of

Question 17

Diagram the degradative pathway from proline to an intermediate of either glycolysis or the citric acid cycle. Show structures of intermediates and indicate where cofactors are involved.

Accepted Answer

The degradative pathway from proline to

Question 18

Which amino acid is catabolized to both succinyl-CoA and acetyl-CoA?

Accepted Answer

A)  leucine 
B)  isoleucine 
C)  lysine 
D)  valine 
E)  both isoleucine and valine 
A)  leucine 
B)  isoleucine 
C)  lysine 
D)  valine 
E)  both isoleucine and valine

Question 19

Which reaction is a hydrolysis reaction?

Accepted Answer

A)  the conversion of arginine into urea and ornithine by arginase 
B)  the conversion of glutamine into glutamate by glutamase 
C)  the conversion of tyrosine into phenylalanine by phenylalanine hydroxylase 
D)  both the conversion of the arginine into urea and ornithine by arginase and the conversion of glutamine into glutamate by glutamase 
E)  both the conversion of glutamine into glutamate by glutamase and the conversion of tyrosine into phenylalanine by phenylalanine hydroxylase 
A)  the conversion of arginine into urea and ornithine by arginase 
B)  the conversion of glutamine into glutamate by glutamase 
C)  the conversion of tyrosine into phenylalanine by phenylalanine hydroxylase 
D)  both the conversion of the arginine into urea and ornithine by arginase and the conversion of glutamine into glutamate by glutamase 
E)  both the conversion of glutamine into glutamate by glutamase and the conversion of tyrosine into phenylalanine by phenylalanine hydroxylase

Question 20

The E3 subunit of pyruvate dehydrogenase, $\alpha$-ketoglutarate dehydrogenase and the branched-chain $\alpha$-keto acid dehydrogenase complex is identical in each multi-enzyme complex. What reaction is catalyzed by this subunit, and why it does it make sense that it is common while E1 and E2 are not?

Accepted Answer

The E3 subunit of pyruvate dehydrogenase

Exam 18: Amino Acid Oxidation and the Production of Urea

Which compound can be described as exclusively ketogenic?

Which amino acid is used to transport nitrogen to the liver?

Which compound can be described as glucogenic?

Methionine synthase uses what substrates to synthesize methionine?

During starvation, more urea production occurs. Explain this observation.

Which statement is TRUE regarding glutamine synthetase?

Outline two paths by which 14N-labeled glutamate can lead to labeled products in the urea cycle.

If 14C-labeled glutamate is introduced into liver cells, what compounds in the urea cycle will be rapidly labeled with the carbon?

In which pair of compounds is the second molecule produced by the deamination of the first molecule?

What processes are associated with the glucose-alanine cycle?

Which amino acid can be considered to be both glucogenic and ketogenic?

Glutamate is metabolically converted to α\alphaα -ketoglutarate and NH4+ by a process described as:

In the human genetic disease maple syrup urine disease, the metabolic defect involves:

Nitrogen from protein is eliminated as what compound in animals?

Which statement is TRUE regarding the conversion of arginine to ornithine in the urea cycle?

Define zymogen and describe the role of one zymogen in protein digestion.

Diagram the degradative pathway from proline to an intermediate of either glycolysis or the citric acid cycle. Show structures of intermediates and indicate where cofactors are involved.

Which amino acid is catabolized to both succinyl-CoA and acetyl-CoA?

Which reaction is a hydrolysis reaction?

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

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

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

Outline two paths by which ¹⁴N-labeled glutamate can lead to labeled products in the urea cycle.

If ¹⁴C-labeled glutamate is introduced into liver cells, what compounds in the urea cycle will be rapidly labeled with the carbon?

Glutamate is metabolically converted to $\alpha$ -ketoglutarate and NH₄⁺ by a process described as: