Unit 4 test UNE medical biochemistry
UPDATED Questions with CORRECT
Answers
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 - CORRECT 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 - CORRECT 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 - CORRECT ANSWER - Carbamoyl phosphate synthetase I
(CPS I)
Feedback: CPS I is the regulatory enzyme of the urea cycle and is stimulated by NAG
Your patient presents with a deficiency of the enzyme that catalyzes synthesis of N-
acetylglutamate (NAGs). Which of the following will be a consequence of this deficiency in the
patient?
a. increased fatty acids in the blood
b. increased amino acids in the blood
c. decreased excretion of uric acid
d. increased glucose in the blood - CORRECT 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 - CORRECT 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 - CORRECT ANSWER - arginine
UPDATED Questions with CORRECT
Answers
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 - CORRECT 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 - CORRECT 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 - CORRECT ANSWER - Carbamoyl phosphate synthetase I
(CPS I)
Feedback: CPS I is the regulatory enzyme of the urea cycle and is stimulated by NAG
Your patient presents with a deficiency of the enzyme that catalyzes synthesis of N-
acetylglutamate (NAGs). Which of the following will be a consequence of this deficiency in the
patient?
a. increased fatty acids in the blood
b. increased amino acids in the blood
c. decreased excretion of uric acid
d. increased glucose in the blood - CORRECT 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 - CORRECT 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 - CORRECT ANSWER - arginine
