Question 1

Which statement is FALSE regarding pepsin?

Accepted Answer

A)  This enzyme is activated by irreversible covalent modification. 
B)  This enzyme is classified as a hydrolase. 
C)  This enzyme is highly active at neutral pH. 
D)  This enzyme is secreted in response to protein ingestion. 
E)  This enzyme has a specificity for cleavage at aromatic amino acids. 
A)  This enzyme is activated by irreversible covalent modification. 
B)  This enzyme is classified as a hydrolase. 
C)  This enzyme is highly active at neutral pH. 
D)  This enzyme is secreted in response to protein ingestion. 
E)  This enzyme has a specificity for cleavage at aromatic amino acids.

Question 2

Suppose you are responsible for formulating the diet for a 4-year-old boy with phenylketonuria. How do you decide what kind and amount of protein to include in the diet?

Accepted Answer

Phenylketonuria (PKU) is a genetic disor

Question 3

The conversion of glutamate to an $\alpha$-keto acid and NH4+:

Accepted Answer

A)  does not require any cofactors. 
B)  is a reductive deamination. 
C)  is accompanied by ATP hydrolysis catalyzed by the same enzyme. 
D)  is catalyzed by glutamate dehydrogenase. 
E)  requires ATP. 
A)  does not require any cofactors. 
B)  is a reductive deamination. 
C)  is accompanied by ATP hydrolysis catalyzed by the same enzyme. 
D)  is catalyzed by glutamate dehydrogenase. 
E)  requires ATP.

Question 4

Which amino acid can be directly converted into a citric acid cycle intermediate by transamination?

Accepted Answer

A)  glutamic acid 
B)  serine 
C)  threonine 
D)  tyrosine 
E)  proline 
A)  glutamic acid 
B)  serine 
C)  threonine 
D)  tyrosine 
E)  proline

Question 5

Which cofactor is typically required in transamination reactions?

Accepted Answer

A)  pyridoxal-phosphate 
B)  coenzyme Q 
C)  biotin 
D)  thiamin pyrophosphate 
E)  nicotinamide adenine dinucleotide 
A)  pyridoxal-phosphate 
B)  coenzyme Q 
C)  biotin 
D)  thiamin pyrophosphate 
E)  nicotinamide adenine dinucleotide

Question 6

Describe the roles of glutamine synthetase and glutaminase in the metabolism of amino groups in mammals.

Accepted Answer

Glutamine synthetase and glutaminase pla

Question 7

If a person's urine contains unusually high concentrations of urea, which diet has he or she probably been eating recently?

Accepted Answer

A)  high carbohydrate, very low protein 
B)  very high carbohydrate, no protein, no fat 
C)  very very high fat, high carbohydrate, no protein 
D)  very high fat, very low protein 
E)  very low carbohydrate, very high protein 
A)  high carbohydrate, very low protein 
B)  very high carbohydrate, no protein, no fat 
C)  very very high fat, high carbohydrate, no protein 
D)  very high fat, very low protein 
E)  very low carbohydrate, very high protein

Question 8

Amino acid catabolism involves the breakdown of 20 amino acids all of which contain nitrogen but have different carbon skeletons. What overall strategy is used to deal with this problem? Illustrate the strategy with two examples.

Accepted Answer

The overall strategy used to deal with t

Question 9

Which compound is NOT transported across the inner mitochondrial membrane as part of either the urea cycle and aspartate-arginosuccinate shunt?

Accepted Answer

A)  fumarate 
B)  aspartate 
C)  ornithine 
D)  citrulline 
E)  neither fumarate nor citrulline 
A)  fumarate 
B)  aspartate 
C)  ornithine 
D)  citrulline 
E)  neither fumarate nor citrulline

Question 10

Serine or cysteine may enter the citric acid cycle as acetyl-CoA after conversion to:

Accepted Answer

A)  oxaloacetate. 
B)  propionate. 
C)  pyruvate. 
D)  succinate. 
E)  succinyl-CoA. 
A)  oxaloacetate. 
B)  propionate. 
C)  pyruvate. 
D)  succinate. 
E)  succinyl-CoA.

Question 11

The amino acids leucine, valine, and isoleucine are preferentially catabolized in muscle tissue, while other amino acids are catabolized primarily in the liver. Given the characteristics of these amino acids, why might this be advantageous? Where in the cell would you expect them to be catabolized?

Accepted Answer

The preferential catabolism of leucine,

Question 12

Which amino acids are converted to α-ketoglutarate?
 
1.  glycine
2.  glutamate
3.  histidine
4.  arginine
5.  proline

Accepted Answer

A) 	1, 3, and 5 
B) 	2, 3, and 4 
C) 	2, 3, and 5 
D) 	2, 3, 4, and 5 
E) 	3, 4, and 5 
A) 	1, 3, and 5 
B) 	2, 3, and 4 
C) 	2, 3, and 5 
D) 	2, 3, 4, and 5 
E) 	3, 4, and 5

Question 13

Give the name of the $\alpha$-keto acid resulting when the following amino acids undergo transamination with $\alpha$-ketoglutarate: (a) glutamate; (b) aspartate; (b) alanine.

Accepted Answer

Transamination is a chemical reaction th

Question 14

Alanine aminotransferase catalyzes the transamination of alanine and $\alpha$-ketoglutarate to pyruvate and glutamate, while aspartate transaminase converts aspartate and $\alpha$-ketoglutarate to oxaloacetate and glutamate. If you have a 50.0-mL reaction volume containing 0.100 M alanine, $\alpha$-ketoglutarate, glutamate, and oxaloacetate, what will the equilibrium concentration of aspartate be? Assume an equilibrium constant of 1.0 for both enzyme-catalyzed reactions.

Accepted Answer

To find the equilibrium concentration of

Question 15

Conversion of serine into glycine requires which cofactor?

Accepted Answer

A)  tetrahydrofolate 
B)  pyridoxal 5' phosphate 
C)  NADH 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  tetrahydrofolate 
B)  pyridoxal 5' phosphate 
C)  NADH 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 16

Transamination from alanine to $\alpha$-ketoglutarate requires the coenzyme:

Accepted Answer

A)  biotin. 
B)  NADH. 
C)  No coenzyme is involved. 
D)  pyridoxal phosphate (PLP). 
E)  thiamine pyrophosphate (TPP). 
A)  biotin. 
B)  NADH. 
C)  No coenzyme is involved. 
D)  pyridoxal phosphate (PLP). 
E)  thiamine pyrophosphate (TPP).

Question 17

The coenzyme required for all transaminations is derived from:

Accepted Answer

A)  niacin. 
B)  pyridoxine (vitamin B6). 
C)  riboflavin. 
D)  thiamin. 
E)  vitamin B12. 
A)  niacin. 
B)  pyridoxine (vitamin B6). 
C)  riboflavin. 
D)  thiamin. 
E)  vitamin B12.

Question 18

Urea synthesis in mammals takes place primarily in tissues of the:

Accepted Answer

A)  brain. 
B)  kidney. 
C)  liver. 
D)  skeletal muscle. 
E)  small intestine. 
A)  brain. 
B)  kidney. 
C)  liver. 
D)  skeletal muscle. 
E)  small intestine.

Question 19

In the treatment of diabetes, insulin is given intravenously. Why can't this hormone, a small protein, be taken orally?

Accepted Answer

Insulin, a hormone used in the treatment

Question 20

Phenylketoneuria is associated with disorders in the catabolism of which amino acid?

Accepted Answer

A)  phenylalanine 
B)  tyrosine 
C)  tryptophan 
D)  histidine 
A)  phenylalanine 
B)  tyrosine 
C)  tryptophan 
D)  histidine

Exam 18: Amino Acid Oxidation and the Production of Urea

Which statement is FALSE regarding pepsin?

Suppose you are responsible for formulating the diet for a 4-year-old boy with phenylketonuria. How do you decide what kind and amount of protein to include in the diet?

The conversion of glutamate to an α\alphaα -keto acid and NH4+:

Which amino acid can be directly converted into a citric acid cycle intermediate by transamination?

Which cofactor is typically required in transamination reactions?

Describe the roles of glutamine synthetase and glutaminase in the metabolism of amino groups in mammals.

If a person's urine contains unusually high concentrations of urea, which diet has he or she probably been eating recently?

Amino acid catabolism involves the breakdown of 20 amino acids all of which contain nitrogen but have different carbon skeletons. What overall strategy is used to deal with this problem? Illustrate the strategy with two examples.

Which compound is NOT transported across the inner mitochondrial membrane as part of either the urea cycle and aspartate-arginosuccinate shunt?

Serine or cysteine may enter the citric acid cycle as acetyl-CoA after conversion to:

The amino acids leucine, valine, and isoleucine are preferentially catabolized in muscle tissue, while other amino acids are catabolized primarily in the liver. Given the characteristics of these amino acids, why might this be advantageous? Where in the cell would you expect them to be catabolized?

Which amino acids are converted to α-ketoglutarate? 1. glycine 2. glutamate 3. histidine 4. arginine 5. proline

Give the name of the α\alphaα -keto acid resulting when the following amino acids undergo transamination with α\alphaα -ketoglutarate: (a) glutamate; (b) aspartate; (b) alanine.

Conversion of serine into glycine requires which cofactor?

Transamination from alanine to α\alphaα -ketoglutarate requires the coenzyme:

The coenzyme required for all transaminations is derived from:

Urea synthesis in mammals takes place primarily in tissues of the:

In the treatment of diabetes, insulin is given intravenously. Why can't this hormone, a small protein, be taken orally?

Phenylketoneuria is associated with disorders in the catabolism of which amino acid?

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

The conversion of glutamate to an $\alpha$ -keto acid and NH₄⁺:

Give the name of the $\alpha$ -keto acid resulting when the following amino acids undergo transamination with $\alpha$ -ketoglutarate: (a) glutamate; (b) aspartate; (b) alanine.

Transamination from alanine to $\alpha$ -ketoglutarate requires the coenzyme: