Question 1

In the digestion of protein that occurs in the small intestine,which enzyme is critical in the activation of zymogens?

Accepted Answer

A) Enteropeptidase 
B) Hexokinase 
C) Papain 
D) Pepsin 
E) Secretin 
A) Enteropeptidase 
B) Hexokinase 
C) Papain 
D) Pepsin 
E) Secretin A

Question 2

Degradation of amino acids yields compounds that are common intermediates in the major metabolic pathways.Explain the distinction between glucogenic and ketogenic amino acids in terms of their metabolic fates.

Accepted Answer

The glucogenic amino acids are those that are catabolized to intermediates that can serve as substrates for gluconeogenesis: pyruvate and any of the four- or five-carbon intermediates of the citric acid cycle.Ketogenic amino acids are catabolized to yield acetyl-CoA or acetoacetyl-CoA,the precursors for ketone body formation.

Question 3

Which of these directly donates a nitrogen atom for the formation of urea during the urea cycle?

Accepted Answer

A) Adenine 
B) Aspartate 
C) Creatine 
D) Glutamate 
E) Ornithine 
A) Adenine 
B) Aspartate 
C) Creatine 
D) Glutamate 
E) Ornithine B

Question 4

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

Accepted Answer

(a)@#LAT-DLM&-ketogl

Question 5

Describe (a)the fundamental nutritional problem faced by individuals with genetic defects in enzymes involved in urea formation and (b)two approaches to treatment of these diseases.

Accepted Answer

(a)A defect in urea synthesis can result

Question 6

The conversion of glutamate to an $\alpha$-ketoacid 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 7

Transamination reactions are catalyzed by a family of enzymes,all of which require __________ as a coenzyme.In the first step of a transamination,the coenzyme in the aldehyde form condenses with the _________ group of an amino acid to form a(n)_________.

Accepted Answer

pyridoxal phosphate

Question 8

Under which circumstances are amino acids not metabolized via oxidative degradation?

Accepted Answer

A) Starvation 
B) Plants growing in nutrient-rich soils 
C) Normal protein turnover 
D) A diet rich in proteins 
E) Uncontrolled diabetes 
A) Starvation 
B) Plants growing in nutrient-rich soils 
C) Normal protein turnover 
D) A diet rich in proteins 
E) Uncontrolled diabetes

Question 9

In the urea cycle,ornithine transcarbamoylase catalyzes:

Accepted Answer

A) cleavage of urea to ammonia. 
B) formation of citrulline from ornithine and another reactant. 
C) formation of ornithine from citrulline and another reactant. 
D) formation of urea from arginine. 
E) transamination of arginine. 
A) cleavage of urea to ammonia. 
B) formation of citrulline from ornithine and another reactant. 
C) formation of ornithine from citrulline and another reactant. 
D) formation of urea from arginine. 
E) transamination of arginine.

Question 10

Describe the three different forms of nitrogen by which different organisms dispose of excess nitrogen obtained in the diet.Give examples of organisms that produce these different forms.

Accepted Answer

(1)Ammonotelic: release into the surroun

Question 11

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 12

Which substance is not involved in the production of urea from NH4+ via the urea cycle?

Accepted Answer

A) Aspartate 
B) ATP 
C) Carbamoyl phosphate 
D) Malate 
E) Ornithine 
A) Aspartate 
B) ATP 
C) Carbamoyl phosphate 
D) Malate 
E) Ornithine

Question 13

The human genetic disease phenylketonuria (PKU)can result from:

Accepted Answer

A) deficiency of protein in the diet. 
B) inability to catabolize ketone bodies. 
C) inability to convert phenylalanine to tyrosine. 
D) inability to synthesize phenylalanine. 
E) production of enzymes containing no phenylalanine. 
A) deficiency of protein in the diet. 
B) inability to catabolize ketone bodies. 
C) inability to convert phenylalanine to tyrosine. 
D) inability to synthesize phenylalanine. 
E) production of enzymes containing no phenylalanine.

Question 14

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 shortest pathway is from p

Question 15

Name four amino acids that can be converted directly (in one step)into pyruvate or a citric acid cycle intermediate,and name the intermediate formed from each.

Accepted Answer

(1)aspartate;oxaloacetate; (2)

Question 16

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

Accepted Answer

First,the biological activity of insulin

Question 17

Which of these is not a protease that acts in the small intestine?

Accepted Answer

A) Chymotrypsin 
B) Elastase 
C) Enteropeptidase 
D) Secretin 
E) Trypsin 
A) Chymotrypsin 
B) Elastase 
C) Enteropeptidase 
D) Secretin 
E) Trypsin

Question 18

Which of the following statements is false in reference to the mammalian synthesis of urea?

Accepted Answer

A) Krebs was a major contributor to the elucidation of the pathway involved. 
B) The amino acid arginine is the immediate precursor to urea. 
C) The carbon atom of urea is derived from mitochondrial HCO3-. 
D) The precursor to one of the nitrogens of urea is aspartate. 
E) The process of urea production is an energy-yielding series of reactions. 
A) Krebs was a major contributor to the elucidation of the pathway involved. 
B) The amino acid arginine is the immediate precursor to urea. 
C) The carbon atom of urea is derived from mitochondrial HCO3-. 
D) The precursor to one of the nitrogens of urea is aspartate. 
E) The process of urea production is an energy-yielding series of reactions.

Question 19

The coenzyme involved in a transaminase reaction is:

Accepted Answer

A) biotin phosphate. 
B) lipoic acid. 
C) nicotinamide adenine dinucleotide phosphate (NADP+). 
D) pyridoxal phosphate (PLP). 
E) thiamine pyrophosphate (TPP). 
A) biotin phosphate. 
B) lipoic acid. 
C) nicotinamide adenine dinucleotide phosphate (NADP+). 
D) pyridoxal phosphate (PLP). 
E) thiamine pyrophosphate (TPP).

Question 20

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

A growing child needs a certain amount o

Exam 18: Amino Acid Oxidation and the Production of Urea

In the digestion of protein that occurs in the small intestine,which enzyme is critical in the activation of zymogens?

Degradation of amino acids yields compounds that are common intermediates in the major metabolic pathways.Explain the distinction between glucogenic and ketogenic amino acids in terms of their metabolic fates.

Which of these directly donates a nitrogen atom for the formation of urea during the urea cycle?

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

Describe (a)the fundamental nutritional problem faced by individuals with genetic defects in enzymes involved in urea formation and (b)two approaches to treatment of these diseases.

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

Transamination reactions are catalyzed by a family of enzymes,all of which require __________ as a coenzyme.In the first step of a transamination,the coenzyme in the aldehyde form condenses with the _________ group of an amino acid to form a(n)_________.

Under which circumstances are amino acids not metabolized via oxidative degradation?

In the urea cycle,ornithine transcarbamoylase catalyzes:

Describe the three different forms of nitrogen by which different organisms dispose of excess nitrogen obtained in the diet.Give examples of organisms that produce these different forms.

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

Which substance is not involved in the production of urea from NH4+ via the urea cycle?

The human genetic disease phenylketonuria (PKU)can result from:

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.

Name four amino acids that can be converted directly (in one step)into pyruvate or a citric acid cycle intermediate,and name the intermediate formed from each.

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

Which of these is not a protease that acts in the small intestine?

Which of the following statements is false in reference to the mammalian synthesis of urea?

The coenzyme involved in a transaminase reaction is:

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 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

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

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

Transamination reactions are catalyzed by a family of enzymes,all of which require ______ as a coenzyme.In the first step of a transamination,the coenzyme in the aldehyde form condenses with the _ group of an amino acid to form a(n)_____.

Which substance is not involved in the production of urea from NH₄⁺ via the urea cycle?