Deck 18: Amino Acid and Nitrogen Metabolism

Question 1

The Krebs-Henseleit urea cycle takes place in liver cells entirely within the mitochondrion.

Answer 1

False

Question 2

Nitrate can be reduced to ammonia by virtually all organisms.

Answer 2

False

Question 3

Which of the following amino acids is both glucogenic and ketogenic?

A) Lysine
B) Leucine
C) Tryptophan
D) Cysteine
E) Arginine

Answer 3

C

Question 4

Transamination reactions can be used to degrade or synthesize amino acids because they have an ________ that has a value close to one.

Question 5

N2 gas can be converted to NH3 by:

A) most organisms.
B) mammals.
C) all plants.
D) all bacteria.
E) legumes.

Question 6

Arginine and methionine can be synthesized by mammals but are generally classed as essential amino acids.

Question 7

With appropriate nutrition, animals maintain nitrogen intake and excretion at equivalent rates.

Question 8

The proteasome is a large multisubunit ATP-dependent protease that degrades proteins that have been modified by the attachment of ________.

Question 9

Pyridoxal phosphate is a versatile coenzyme as it is capable of forming a stable ________ base between an amino acid substrate and the coenzyme.

Question 10

Nitrogen fixation requires the hydrolysis of 8 ATPs to produce 2 NH3 molecules from 1 N2.

Question 11

The common degradation product of lysine, tryptophan, phenylalanine and tyrosine is ________.

Question 12

The H2S produced by metabolism of cysteine is a waste product with no physiological or biochemical function.

Question 13

Which of the following enzymes is NOT involved in the conversion of NH3 to an organic nitrogen-containing compound?

A) Glutamate dehydrogenase
B) Carbamoyl phosphate dehydrogenase
C) Glutamate-oxaloacetate transaminase
D) Glutamine synthetase
E) Asparagine synthetase

Question 14

Which of the following amino acids cannot be used to provide an intermediate of the citric acid cycle?

A) Histidine
B) Proline
C) Phenylalanine
D) Lysine
E) Tyrosine

Question 15

The oxidation of branched chain amino acids shares a similar chemical strategy with β-oxidation of fatty acids.

Question 16

In the degradation of amino acids in muscle NH4+ is carried to the liver for conversion into urea by:

A) glutamine.
B) asparagine.
C) alanine.
D) either alanine or glutamine.
E) any amino acid.

Question 17

All amino acids can be synthesized from intermediates of the:

A) glycolytic pathway alone.
B) glycolytic pathway and the pentose phosphate pathway.
C) citric acid cycle alone.
D) the glycolytic pathway and citric acid cycle.
E) the glycolytic pathway, the pentose phosphate pathway and citric acid cycle.

Question 18

________ high energy phosphates from ATP are consumed in each turn of the urea cycle.

Question 19

Tetrahydrofolate is a coenzyme involved in the mobilization and utilization of single carbon functional units in the:

A) metabolism of serine, glycine, methionine, and histidine.
B) biosynthesis of purine nucleotides.
C) biosynthesis of thymine.
D) biosynthesis of formylmethionyl-tRNA.
E) all of the above.

Question 20

In mammals excess dietary protein is degraded with amino acid nitrogen being excreted as ________.

Question 21

Folate deficiency results in increased risk of cardiovascular disease associated with abnormally high levels of serum ________ due to decreased levels of tetrahydrofolate cofactors required for the methionine synthase reaction.

Question 22

The catecholamine neurotransmitters are derived from ________.

Question 23

Apart from in the synthesis of methionine, S-adenosylmethionine is the only biological ________ group donor.

Question 24

Tyrosine is the precursor of serotonin which has a number of roles in the nervous system.