Unit 4 test UNE medical biochemistry Prep
Exam Questions Fully Solved.
A deficiency in which of the following enzymes will NOT result in an increase in orotic acid?
a. N-acetylglutamate synthetase
b. Ornithine transcarbamoylase
c. Argininosuccinate synthetase
d. Argininosuccinate lyase - Answer N-acetylglutamate synthetase (NAG synthetase
Feedback: deficiencies in NAG synthetase or carbamoyl phosphate synthetase I will NOT result
in an increase in orotic acid.
Which of the following enzymes is correctly paired with its activator?
a. N-acetylglutamate synthtase; arginine
b. Carbamoyl phosphate synthetase I; ATP
c. Glutaminase; citrate
d. Arginase; NADH - Answer N-acetylglutamate synthtase; arginine
Feedback: arginine (an intermediate of the urea cycle), stimulates the synthesis of NAG by
allosterically activating the enzyme N-acetylglutamate synthase
Which of the following enzymes is regulated by N-acetylglutamate (NAGs)?
a. Carbamoyl phosphate synthetase II
b. Ornithine transcarbamoylase
c. Carbamoyl phosphate synthetase I
d. Arginosuccinate lyase - Answer Carbamoyl phosphate synthetase I (CPS I)
Feedback: CPS I is the regulatory enzyme of the urea cycle and is stimulated by NAG
, c. decreased excretion of uric acid
d. increased glucose in the blood - Answer Increased amino acids in the blood
NAG is an essential activator of CPS I which catalyzes the first step in the urea cycle. Loss of this
activator will decrease urea cycle activity, which will increase the amount of amino acids in the
blood.
The urea cycle takes place in which of the following subcellular locations?
a. the cytosol and the mitochondria
b. the cytosol only
c. the nucleus and the mitochondria
d. the mitochondria only - Answer the cytosol and the mitochondria
Which of the following non-essential amino acids is synthesized as part of the urea cycle?
a. Asparagine
b. Aspartate
c. Lysine
d. Arginine
e. Glutamine - Answer arginine
Several amino acids are intermediates of the urea cycle, having side ammonia groups that join
with free Co2 and ammonia to produce net excretion of ammonia as urea. Which of the
following amino acids has a nitrogen in its side chain AND is an intermediate of the urea cycle?
a. asparagine
b. glutamate
c. phenylalanine
d. arginine - Answer arginine
Which of the following reactions of the urea cycle takes place in the mitochondria?
a. the synthesis of urea
b. the synthesis of argininosuccinate
c. the synthesis of carbamoyl phosphate
Exam Questions Fully Solved.
A deficiency in which of the following enzymes will NOT result in an increase in orotic acid?
a. N-acetylglutamate synthetase
b. Ornithine transcarbamoylase
c. Argininosuccinate synthetase
d. Argininosuccinate lyase - Answer N-acetylglutamate synthetase (NAG synthetase
Feedback: deficiencies in NAG synthetase or carbamoyl phosphate synthetase I will NOT result
in an increase in orotic acid.
Which of the following enzymes is correctly paired with its activator?
a. N-acetylglutamate synthtase; arginine
b. Carbamoyl phosphate synthetase I; ATP
c. Glutaminase; citrate
d. Arginase; NADH - Answer N-acetylglutamate synthtase; arginine
Feedback: arginine (an intermediate of the urea cycle), stimulates the synthesis of NAG by
allosterically activating the enzyme N-acetylglutamate synthase
Which of the following enzymes is regulated by N-acetylglutamate (NAGs)?
a. Carbamoyl phosphate synthetase II
b. Ornithine transcarbamoylase
c. Carbamoyl phosphate synthetase I
d. Arginosuccinate lyase - Answer Carbamoyl phosphate synthetase I (CPS I)
Feedback: CPS I is the regulatory enzyme of the urea cycle and is stimulated by NAG
, c. decreased excretion of uric acid
d. increased glucose in the blood - Answer Increased amino acids in the blood
NAG is an essential activator of CPS I which catalyzes the first step in the urea cycle. Loss of this
activator will decrease urea cycle activity, which will increase the amount of amino acids in the
blood.
The urea cycle takes place in which of the following subcellular locations?
a. the cytosol and the mitochondria
b. the cytosol only
c. the nucleus and the mitochondria
d. the mitochondria only - Answer the cytosol and the mitochondria
Which of the following non-essential amino acids is synthesized as part of the urea cycle?
a. Asparagine
b. Aspartate
c. Lysine
d. Arginine
e. Glutamine - Answer arginine
Several amino acids are intermediates of the urea cycle, having side ammonia groups that join
with free Co2 and ammonia to produce net excretion of ammonia as urea. Which of the
following amino acids has a nitrogen in its side chain AND is an intermediate of the urea cycle?
a. asparagine
b. glutamate
c. phenylalanine
d. arginine - Answer arginine
Which of the following reactions of the urea cycle takes place in the mitochondria?
a. the synthesis of urea
b. the synthesis of argininosuccinate
c. the synthesis of carbamoyl phosphate
