Unit 4 Test UNE Medical Biochemistry – Q/A (Rated A+)
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 Ans - 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 Ans - 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 Ans - 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 Ans - 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 Ans - 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 Ans - 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 Correct Ans - 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
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 Ans - 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 Ans - 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 Ans - 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 Ans - 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 Ans - 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 Ans - 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 Correct Ans - 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
