Question 1

How is the urea cycle linked to the citric acid cycle?

Accepted Answer

During the urea cycle, aspartate brings in the second nitrogen by combining with citrulline to form argininosuccinate. Then argininosuccinate is cleaved, forming arginine and fumarate. The fumarate is then converted into malate and then oxidized to oxaloacetate, which can be transaminated to aspartate or serve as a precursor to glucose. Fumarate, malate, and oxaloacetate are all intermediates of the citric acid cycle. Figure 30.3 in the text shows this integration.

Question 2

Describe the glucose-alanine cycle and its significance in amino acid metabolism.

Accepted Answer

During prolonged exercise and fasting, muscles use branched-chain amino acids as fuel. This degradation takes place in the muscle, but conversion to urea is not possible in this tissue, thus transport to the liver is required. The amino nitrogen is removed by transamination to produce glutamate. The glutamate then transaminates with pyruvate, producing alanine, which is released into the blood and transported to the liver. In the liver, the alanine is converted to pyruvate and the urea is metabolized to urea. The pyruvate is converted to glucose by gluconeogenesis and the glucose is transported back to the muscle via the bloodstream.

Question 3

Use the following to answer questions 
Choose the correct answer from the list below. Not all of the answers will be used.
-The molecule _______________ is oxidatively deaminated to an ammonium ion.

Accepted Answer

A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder 
A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder H

Question 4

Which amino acids can be converted to pyruvate by a single enzyme-catalyzed reaction?

Accepted Answer

Alanine can be converted to py

Question 5

Use the following to answer questions 
Choose the correct answer from the list below. Not all of the answers will be used.
-The molecule _______________ is formed from excess NH4+ by ureotelic organisms.

Accepted Answer

A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder 
A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder

Question 6

Which of the following amino acids is/are ketogenic?

Accepted Answer

A)  asparagine 
B)  methionine 
C)  valine 
D)  lysine 
E)  A, B, and C 
A)  asparagine 
B)  methionine 
C)  valine 
D)  lysine 
E)  A, B, and C

Question 7

Which of the following amino acids is/are glucogenic?

Accepted Answer

A)  asparagine 
B)  methionine 
C)  valine 
D)  lysine 
E)  A, B, and C 
A)  asparagine 
B)  methionine 
C)  valine 
D)  lysine 
E)  A, B, and C

Question 8

Which amino acid(s) is/are converted to tyrosine in the degradative pathway?

Accepted Answer

A)  phenylalanine 
B)  tryptophan 
C)  methionine 
D)  A and B 
E)  A, B, and C 
A)  phenylalanine 
B)  tryptophan 
C)  methionine 
D)  A and B 
E)  A, B, and C

Question 9

Use the following to answer questions 
Choose the correct answer from the list below. Not all of the answers will be used.
-The methyl group donor _______________ is the product of the first step of methionine degradation.

Accepted Answer

A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder 
A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder

Question 10

Write the net equation of the urea cycle and indicate whether energy is produced or consumed by the cycle.

Accepted Answer

CO2 + NH4+ + 3 ATP + Asp + 2 H

Question 11

The genetic deficiency of the enzyme ___________________ results in a condition referred to as phenylketonuria.

Accepted Answer

phenylalan

Question 12

Why are more uricotelic organisms found in the desert than in the tropics?

Accepted Answer

Uricotelic organisms remove to

Question 13

Use the following to answer questions 
Choose the correct answer from the list below. Not all of the answers will be used.
-Serine and threonine are deaminated by the enzyme _______________.

Accepted Answer

A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder 
A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder

Question 14

Surplus amino acids are:

Accepted Answer

A)  stored in proteasomes. 
B)  stored in protein scaffolds. 
C)  used as metabolic fuel. 
D)  All of the above. 
E)  None of the above. 
A)  stored in proteasomes. 
B)  stored in protein scaffolds. 
C)  used as metabolic fuel. 
D)  All of the above. 
E)  None of the above.

Question 15

Ammoniotelic organisms excrete excess nitrogen as:

Accepted Answer

A)  N2H8. 
B)  NH4+. 
C)  urea. 
D)  All of the above. 
E)  None of the above. 
A)  N2H8. 
B)  NH4+. 
C)  urea. 
D)  All of the above. 
E)  None of the above.

Question 16

Which of the following is an allosteric activator of mammalian carbamoyl phosphate synthetase?

Accepted Answer

A)  α-ketoglutarate 
B)  N-acetylaspartate 
C)  N-acetylglutamate 
D)  glutamine 
E)  None of the above. 
A)  α-ketoglutarate 
B)  N-acetylaspartate 
C)  N-acetylglutamate 
D)  glutamine 
E)  None of the above.

Question 17

Use the following to answer questions 
Choose the correct answer from the list below. Not all of the answers will be used.
-The _______________ enzyme catalyzes an oxidative deamination and can utilize either NAD+ or NADP+.

Accepted Answer

A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder 
A) hyperammonemia 
B) aminotransferases 
C) methionine 
D) S-adenosylmethionine 
E) glutamate dehydrogenase
F)oxaloacetate
G)biopterin
H)glutamate
I)hippurate
J)urea
K)dehydratase
L)dioxygenases
M)ammonia disorder

Question 18

In the urea cycle, the second nitrogen of urea enters the cycle in the form of which of the following metabolites?

Accepted Answer

A)  alanine 
B)  glutamine 
C)  ornithine 
D)  aspartate 
E)  arginine 
A)  alanine 
B)  glutamine 
C)  ornithine 
D)  aspartate 
E)  arginine

Question 19

What is the cause of PKU? Give the structure of the abnormal metabolite that accumulates from which this condition gets its name.

Accepted Answer

PKU is the abbreviation for phenylketonu

Question 20

Oxidative deamination of glutamate results in free ammonium ions and ___________________.

Accepted Answer

The answer of Oxidative deamination of glutamate results in free...

Exam 30: Amino Acid Degradation and the Urea Cycle

How is the urea cycle linked to the citric acid cycle?

Describe the glucose-alanine cycle and its significance in amino acid metabolism.

Use the following to answer questions Choose the correct answer from the list below. Not all of the answers will be used. -The molecule _______________ is oxidatively deaminated to an ammonium ion.

Which amino acids can be converted to pyruvate by a single enzyme-catalyzed reaction?

Use the following to answer questions Choose the correct answer from the list below. Not all of the answers will be used. -The molecule _______________ is formed from excess NH4+ by ureotelic organisms.

Which of the following amino acids is/are ketogenic?

Which of the following amino acids is/are glucogenic?

Which amino acid(s) is/are converted to tyrosine in the degradative pathway?

Use the following to answer questions Choose the correct answer from the list below. Not all of the answers will be used. -The methyl group donor _______________ is the product of the first step of methionine degradation.

Write the net equation of the urea cycle and indicate whether energy is produced or consumed by the cycle.

The genetic deficiency of the enzyme ___________________ results in a condition referred to as phenylketonuria.

Why are more uricotelic organisms found in the desert than in the tropics?

Use the following to answer questions Choose the correct answer from the list below. Not all of the answers will be used. -Serine and threonine are deaminated by the enzyme _______________.

Surplus amino acids are:

Ammoniotelic organisms excrete excess nitrogen as:

Which of the following is an allosteric activator of mammalian carbamoyl phosphate synthetase?

Use the following to answer questions Choose the correct answer from the list below. Not all of the answers will be used. -The _______________ enzyme catalyzes an oxidative deamination and can utilize either NAD+ or NADP+.

In the urea cycle, the second nitrogen of urea enters the cycle in the form of which of the following metabolites?

What is the cause of PKU? Give the structure of the abnormal metabolite that accumulates from which this condition gets its name.

Oxidative deamination of glutamate results in free ammonium ions and ___________________.

Biochemistry and the Unity of Life

Water, Weak Bonds, and the Generation of Order Out of Chaos

Amino Acids

Protein Three-Dimensional Structure

Techniques in Protein Biochemistry

Basic Concepts of Enzyme Action

Kinetics and Regulation

Mechanisms and Inhibitors

Hemoglobin: an Allosteric Protein

Carbohydrates

Lipids

Membrane Structure and Function

Signal Transduction Pathways

Digestion: Turning a Meal Into Cellular Biochemicals

Metabolism: Basic Concepts and Design

Glycolysis

Gluconeogenesis

Preparation for the Cycle

Harvesting Electrons From the Cycle

The Electron Transport Chain

The Proton-Motive Force

The Light Reactions

The Calvin Cycle

Glycogen Degradation

Glycogen Synthesis

The Pentose Phosphate Pathway

Fatty Acid Degredation

Fatty Acid Synthesis

Lipid Synthesis

Amino Acids Synthesis

Nucleotide Metabolism

The Structure of Informational Macromolecules: Dna and Rna

DNA Replication

DNA Repair and Recombination

RNA Synthesis and Regulation in Prokaryotes

Gene Expression in Eukaryotes

RNA Processing in Eukaryotes

The Genetic Code

The Mechanism of Protein Synthesis

Recombinant Dna Techniques

Filters