A) cleaves chymotrypsinogen to form chymotrypsin
B) neutralizes the pH of the duodenum to a pH of 7
C) cleaves trypsinogen to form trypsin
D) generates peptides and amino acids
C) cleaves trypsinogen to form trypsin
Which of the three proteins in the ubiquination pathway is the most responsible
for recognizing the ubiquintated target protein?
E1
E2
E3
all three of the proteins recognize the target protein
E3
What is the regulatory mechanism by which arginine stimulates flux through the
urea cycle?
A) arginine stimulates flux through the urea cycle by inhibiting the enzyme
nitrogenase
B) arginine stimulates the production of N-acetylglutamate which activates
arginase
C) arginine stimulates the activity of carbonyl phosphate synthetase I
D) arginine stimulates the production of the allosteric activator N-acetylglutamate
D) arginine stimulates the production of the allosteric activator N-acetylglutamate
,A person who has alkaptonuria is easily diagnosed from their black urine. What
causes the black color?
reduction of acetoacetyl-CoA
phenylpyruvate and phenylacetate
oxidation of homogentisate
oxidation of phenylalanine
oxidation of homogentisate
The twenty amino acids needed for protein synthesis can be categorized in animals
as essential or nonessential with regard to dietary sources.
a) What is a characteristic of the biosynthetic pathways needed to generate
essential amino acids?
b) Why is arginine an essential amino acid even though it is generated by arginase
in the urea cycle?
c) Why is tyrosine a nonessential amino acid in animals even though they do not
contain shikimate pathway enzymes?
a) metabolic pathways to synthesize essential amino acids require many enzymes
b) arginase does not generate enough arginine in the urea cycle to support protein
synthesis
c) tyrosine is synthesized de novo by the same enzymes that synthesize alanine
and pyruvate
a) metabolic pathways to synthesize essential amino acids require NADPH;
pathways for nonessential amino acid pathways require NADH
b) arginase does not generate enough arginine in the urea cycle to support protein
synthesis
c) tyrosine is generated from phenylalanine, which is an essential amino acid in
animals
,a) metabolic pathways to synthesize essential amino acids require many enzymes
b) even though arginine is synthesized in animals by de novo pathways it is
consumed by the urea cycle
c) tyrosine is generated from phenylalanine, which is an essential amino acid in
animals
a) metabolic pathways to synthesize essential amino acids require many enzymes
b) arginase does not generate enough arginine in the urea cycle to support protein
synthesis
c) tyrosine is generated from phenylalanine, which is an essential amino acid in
animals
a) metabolic pathways to synthesize essential amino acids require very few
enzymes
b) arginase generates enough arginine for protein synthesis, however it is
degraded by glyphosate
c) tyrosine is generated from tryptophan, which is an essential amino acid in
animals
a) metabolic pathways to synthesize essential amino acids require many enzymes
b) arginase does not generate enough arginine in the urea cycle to support protein
synthesis
c) tyrosine is generated from phenylalanine, which is an essential amino acid in
animals
What is the biochemical basis for giving individuals with hyperammonemia
phenylbutyrate?
A) Phenylbutyrate treatment leads to the production of phenylacetylglutamine,
which is a soluble metabolite that reduces ammonia levels by removing glutamine.
, B) Phenylbutyrate treatment is used to reduce hyperammonemia by stimulating
the expression of genes involved in nitrogen fixation and assimilation.
C) Phenylbutyrate treatment leads to the production of phenylacetylglutamate,
which is a soluble metabolite that reduces ammonia levels by removing glutamate.
D) Phenylbutyrate treatment removes ammonia by forming an insoluble
precipitate that is excreted in the feces, which alleviates the symptoms of
hyperammonemia.
E) Phenylbutyrate treatment leads to the production of argininosuccinate, which is
a soluble metabolite that reduces ammonia levels by removing aspartate.
A) Phenylbutyrate treatment leads to the production of phenylacetylglutamine,
which is a soluble metabolite that reduces ammonia levels by removing glutamine.
t has been observed that some individuals with PKU have lighter skin than other
individuals with PKU. What contributing factors explain this difference in
pigmentation?
A) The severity of the phenylalanine hydroxylase deficiency and the amount of
tyrosine in the diet of the individual.
B) The severity of the phenylalanine hydroxylase deficiency and the amount of
time the individual with PKU is exposed to sunlight.
C) Some PKU individuals are also albinos and this affects the amount of
phenylalanine they can have in their diet.
D) The amount of phenylalanine in the diet and the amount of time the individual
with PKU is exposed to sunlight.
E) Some PKU individuals are also albinos, while other individuals consume high
levels of dietary protein.
A) The severity of the phenylalanine hydroxylase deficiency and the amount of
tyrosine in the diet of the individual.
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