Deck 30: Amino Acid Degradation and the Urea Cycle

Question 1

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
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
The ______________ enzymes transfer an ɑ-amino group from amino acids to ɑ-ketoglutarate.

Answer 1

b

Question 2

The urea cycle is linked to gluconeogenesis via formation of ___________________, a precursor of glucose synthesis.

Answer 2

fumarate

Question 3

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

Answer 3

phenylalanine hydroxylase

Question 4

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

Question 5

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
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
_______________ is caused by defects in the urea cycle, which lead to an elevated level of ammonia in blood.

Question 6

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

Question 7

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

Question 8

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
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
The product _______________ results when aspartate is transaminated with ɑ-ketoglutarate.

Question 9

In the first step of the urea cycle, CO2 and NH4+ are converted into ___________________.

Question 10

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

Question 11

The hydrolysis of arginine by arginase produces ornithine and ___________________.

Question 12

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

Question 13

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

Question 14

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
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
The class of enzymes that cleaves most aromatic rings in biological systems is _____________.

Question 15

In adults, the urea cycle produces sufficient quantities of ___________________ so that it is not considered an essential amino acid.

Question 16

Nitrogen is transported from muscle to liver in the form of ___________________or _______________.

Question 17

Serine dehydratase catalyzes the conversion of serine into NH4+ and ___________________.

Question 18

In the degradation of amino acids, the amino nitrogens can eventually become the amino group of ___________________.

Question 19

___________________ is the prosthetic group used in deaminations by dehydratases.

Question 20

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
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
The cofactor required by phenylalanine hydroxylase is _______________.

Question 21

Which amino acid(s) is/are metabolites in the urea cycle, but is/are not used as (a) building block(s) of proteins?

A) ornithine
B) citrulline
C) glutamate
D) A and B
E) A, B, and C

Question 22

Surplus amino acids are:

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 23

Ammoniotelic organisms excrete excess nitrogen as:

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

Question 24

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

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

Question 25

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

Question 26

Which amino acids supply carbons for eventual entry into metabolism as succinyl CoA?

A) Methionine, Valine, Leucine
B) Methionine, Isoleucine, Valine
C) Isoleucine, Valine, Leucine
D) All of the above.
E) None of the above.

Question 27

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

Question 28

Uricotelic organisms release nitrogen as:

A) NH4+.
B) arginine.
C) uric acid.
D) All of the above.
E) None of the above.

Question 29

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

Question 30

Which of the following amino acids is/are glucogenic?

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

Question 31

In the urea cycle, the carbon skeleton of aspartate is preserved as:

A) succinate.
B) fumarate.
C) urea.
D) All of the above.
E) None of the above.

Question 32

Ketogenic amino acids are degraded to which of the following metabolites?

A) pyruvate
B) acetyl CoA
C) acetoacetate
D) All of the above.
E) B and C

Question 33

Which amino acids can be directly deaminated to produce NH4+?

A) serine and threonine
B) serine, asparagine, and threonine
C) proline and threonine
D) serine and valine
E) None of the above.

Question 34

What are they?

Question 35

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

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

Question 36

In the urea cycle, free NH4+ is coupled with carboxyphosphate to form:

A) uretic phosphate.
B) pyruvate.
C) carbamic acid.
D) All of the above.
E) None of the above

Question 37

Which of the following amino acids is/are ketogenic?

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

Question 38

Why do you think that weight lifters take large amounts of branched-chain amino acids?

Question 39

The urea cycle is:

A) a system for protein degradation and turnover.
B) responsible for nitrogen fixing.
C) responsible for the filtering of nitrogen by the kidney.
D) a system involved in transporting nitrogen from muscle to the liver.
E) None of the above.

Question 40

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

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

Question 41

What is the basic strategy by which proteins are degraded?

Question 42

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

Question 43

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

Question 44

What type of damage occurs if there is a defect in the urea cycle?

Question 45

What general feature is involved in the degration of aromatic amino acids?

Question 46

Why is biopterin not considered a vitamin?

Question 47

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