Question 1

Show the reaction in which ammonia is formed from glutamate;include any required cofactors and/or intermediates.

Accepted Answer

This is the reaction

Question 2

Describe (briefly)the role of (a)gastrin, (b)pepsinogen, (c)cholecystokinin,and (d)enteropeptidase in protein digestion.

Accepted Answer

(a)The hormone gastrin stimulates secret

Question 3

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

Nitrogen is removed by transam

Question 4

Which of the following reactions involving an amino acid cannot be catalyzed via a PLP-dependent mechanism?

Accepted Answer

A) Hydrolysis 
B) Decarboxylation 
C) Racemization 
D) Transamination 
E) Transimination 
A) Hydrolysis 
B) Decarboxylation 
C) Racemization 
D) Transamination 
E) Transimination

Question 5

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 6

Name one amino acid whose oxidation proceeds via the intermediate shown: (a)pyruvate; (b)oxaloacetate; (c)$\alpha$-ketoglutarate; (d)succinyl-CoA; (e)fumarate.

Accepted Answer

The question asks to name one amino aci

Question 7

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

Accepted Answer

In tissues that are metabolizing the car

Question 8

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 9

Which of the following amino acids are essential for humans?

Accepted Answer

A) Alanine 
B) Aspartic acid 
C) Asparagine 
D) Serine 
E) Threonine 
A) Alanine 
B) Aspartic acid 
C) Asparagine 
D) Serine 
E) Threonine

Question 10

Explain why one might provide high concentrations of the amino acid Arg to patients who have a deficiency in one of the first three enzymes of the urea cycle.

Accepted Answer

The Arg is converted efficiently to urea

Question 11

The amino acids serine,alanine,and cysteine can be catabolized to yield:

Accepted Answer

A) fumarate. 
B) pyruvate. 
C) succinate. 
D) ($\alpha$-ketoglutarate.) 
E) None of the above 
A) fumarate. 
B) pyruvate. 
C) succinate. 
D) ($\alpha$-ketoglutarate.) 
E) None of the above

Question 12

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

Accepted Answer

A zymogen is an inactive form of an enzy

Question 13

If you received a laboratory report showing the presence of a high concentration of phenylalanine and its metabolites in the urine of a patient,what disease would you suspect? What defect(s)in metabolism account(s)for the accumulation of phenylalanine in such patients?

Accepted Answer

Phenylketonuria,the disease th

Question 14

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 15

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 16

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

Accepted Answer

During starvation,cellular proteins are

Question 17

Which of the following is not true of the reaction catalyzed by glutamate dehydrogenase?

Accepted Answer

A) It is similar to transamination in that it involves the coenzyme pyridoxal phosphate (PLP). 
B) NH4+ is produced. 
C) The enzyme can use either NAD+ or NADP+ as a cofactor. 
D) The enzyme is glutamate-specific,but the reaction is involved in oxidizing other amino acids. 
E) ($\alpha$-Ketoglutarate is produced from an amino acid.) 
A) It is similar to transamination in that it involves the coenzyme pyridoxal phosphate (PLP). 
B) NH4+ is produced. 
C) The enzyme can use either NAD+ or NADP+ as a cofactor. 
D) The enzyme is glutamate-specific,but the reaction is involved in oxidizing other amino acids. 
E) ($\alpha$-Ketoglutarate is produced from an amino acid.)

Question 18

Why does a mammal go to all of the trouble of making urea from ammonia rather than simply excreting ammonia as many bacteria do?

Accepted Answer

When bacteria release ammonia into the s

Question 19

Which of these amino acids 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 20

Describe the reactions and the role of the glucose-alanine cycle.

Accepted Answer

Toxic ammonia formed by amino acid catab

Exam 18: Amino Acid Oxidation and the Production of Urea

Show the reaction in which ammonia is formed from glutamate;include any required cofactors and/or intermediates.

Describe (briefly)the role of (a)gastrin, (b)pepsinogen, (c)cholecystokinin,and (d)enteropeptidase in protein digestion.

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 of the following reactions involving an amino acid cannot be catalyzed via a PLP-dependent mechanism?

The coenzyme required for all transaminations is derived from:

Name one amino acid whose oxidation proceeds via the intermediate shown: (a)pyruvate; (b)oxaloacetate; (c) α\alphaα -ketoglutarate; (d)succinyl-CoA; (e)fumarate.

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

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

Which of the following amino acids are essential for humans?

Explain why one might provide high concentrations of the amino acid Arg to patients who have a deficiency in one of the first three enzymes of the urea cycle.

The amino acids serine,alanine,and cysteine can be catabolized to yield:

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

If you received a laboratory report showing the presence of a high concentration of phenylalanine and its metabolites in the urine of a patient,what disease would you suspect? What defect(s)in metabolism account(s)for the accumulation of phenylalanine in such patients?

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

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

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

Which of the following is not true of the reaction catalyzed by glutamate dehydrogenase?

Why does a mammal go to all of the trouble of making urea from ammonia rather than simply excreting ammonia as many bacteria do?

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

Describe the reactions and the role of the glucose-alanine cycle.

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

Recombinant Dna Technology

Lipids

Biological Membranes and Transport

Biosignaling

Principles of Bioenergetics

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

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

Name one amino acid whose oxidation proceeds via the intermediate shown: (a)pyruvate; (b)oxaloacetate; (c) $\alpha$ -ketoglutarate; (d)succinyl-CoA; (e)fumarate.

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