UNE Biochem Unit 4 Multiple Choice Questions With
100% Complete Answers.
Which of the following non-essential amino acids is synthesized as part of the
urea cycle?
Arginine
Which of the following reactions of the urea cycle takes place in the
mitochondria?
The synthesis of carbamoyl phosphate
The transamination of all amino acids requires which of the following cofactors?
Pyridoxal phosphate (PLP)
A comatose infant is brought to the ER. In the course of the examination, plasma
ammonia was found to be elevated 20-fold over normal values. Urine orotic acid
and uracil were both greater than normal. A defect of which of the following
enzymes is the most likely diagnosis?
Ornithine transcarbamoylase
Which of the following enzymes is likely to be active in both the fed and fasted
states?
Glutaminase
The reaction of ammonia with α-ketoglutarate is catalyzed by _________ and
requires _________ as a reactant.
Glutamate dehydrogenase; NADH or NADPH
Which of the following enzymes is regulated by N-acetylglutamate (NAGs)?
Carbamoyl phosphate synthetase I (CPS I)
Your patient presents with a deficiency of the enzyme that catalyzes synthesis of
N-acetylglutamate (NAGs). Which of the following would be a consequence of this
deficiency in the patient?
Increased amino acids in the blood
Homocystinuria can be caused by several different enzyme or vitamin
deficiencies. An elevation of homocysteine and a decrease in cysteine would
most likely present due to which of the following deficiencies?
Loss of function of cystathionine-β synthase
A 15-year-old female presents to her pediatrician with concerns over her inability
to sleep, increased feelings of depression and generalized fatigue. A full
laboratory work-up is ordered and based on these findings she is diagnosed with
a melatonin deficiency. Based on this information, metabolism of which of the
following amino acids is likely impaired?
Tryptophan
In an individual with a deficiency in the branched chain ketoacid dehydrogenase
complex, metabolism of which of the following amino acids would not likely be
impaired?
Tyrosine
A 52-year- old male sought medical help complaining about progressive
appearance of hyperchromic (hyper pigmented) papules on the edge of the
second finger of both hands. He also complained about darkening of urine.
, Incisional biopsy of one of the spots on his hands and urine sample tested
positive for or homogentisic acid. Based on these findings a diagnosis of
alkaptonuria is made. This diagnosis is consistent with a deficiency in which of
the following enzymes?
Homogentisate oxidase
Which of the following compounds or substrates is required for the synthesis of
tyrosine? (+ indicates the compound is required; - indicates the compound is not
required)
(THF) (BH4) Tryptophan Phenylalanine
1. + + + -
2. - + + -
3. + - - +
4. - + - +
4
An individual is suspected of having a deficiency in branched chain keto acid
dehydrogenase. Supplementation of which of the following vitamins or cofactors
may help resolve this issue?
Thiamine
A 2-day-old infant test positive for hyperphenylalaninemia. This is most likely
caused by a heritable defect in which of the following enzymes?
Phenylalanine hydroxylase
A deficiency in B6 (pyridoxal phosphate) would negatively impact which of the
following pathways:
1. Metabolism of homocysteine to cysteine
2. Metabolism of phenylalanine to tyrosine
3. Conversion of methyl malonyl-CoA to succinyl-CoA
1 only
The ribonucleotide reductase is important for converting ribose bases to the
deoxy form. This conversion is coupled with the oxidation of which of the
following compounds?
Thioredoxin
A patient recently diagnosed with colon cancer is being treated with 5-
fluorouracil. Which of the following enzymes will this drug directly inhibit?
Thymidylate synthase
Purine biosynthesis starts with the activation of a 5-carbon sugar. In this initial
reaction, ribose 5-phosphate is converted into which of the following
compounds?
PRPP (5- phosphoribosylpyrophosphate)
In the salvage of purines, hypoxanthine-guanine phosphoribosyl transferase
(HGPRT) is responsible for which of the following processes?
Conversion of guanine to guanosine monophosphate (GMP)
100% Complete Answers.
Which of the following non-essential amino acids is synthesized as part of the
urea cycle?
Arginine
Which of the following reactions of the urea cycle takes place in the
mitochondria?
The synthesis of carbamoyl phosphate
The transamination of all amino acids requires which of the following cofactors?
Pyridoxal phosphate (PLP)
A comatose infant is brought to the ER. In the course of the examination, plasma
ammonia was found to be elevated 20-fold over normal values. Urine orotic acid
and uracil were both greater than normal. A defect of which of the following
enzymes is the most likely diagnosis?
Ornithine transcarbamoylase
Which of the following enzymes is likely to be active in both the fed and fasted
states?
Glutaminase
The reaction of ammonia with α-ketoglutarate is catalyzed by _________ and
requires _________ as a reactant.
Glutamate dehydrogenase; NADH or NADPH
Which of the following enzymes is regulated by N-acetylglutamate (NAGs)?
Carbamoyl phosphate synthetase I (CPS I)
Your patient presents with a deficiency of the enzyme that catalyzes synthesis of
N-acetylglutamate (NAGs). Which of the following would be a consequence of this
deficiency in the patient?
Increased amino acids in the blood
Homocystinuria can be caused by several different enzyme or vitamin
deficiencies. An elevation of homocysteine and a decrease in cysteine would
most likely present due to which of the following deficiencies?
Loss of function of cystathionine-β synthase
A 15-year-old female presents to her pediatrician with concerns over her inability
to sleep, increased feelings of depression and generalized fatigue. A full
laboratory work-up is ordered and based on these findings she is diagnosed with
a melatonin deficiency. Based on this information, metabolism of which of the
following amino acids is likely impaired?
Tryptophan
In an individual with a deficiency in the branched chain ketoacid dehydrogenase
complex, metabolism of which of the following amino acids would not likely be
impaired?
Tyrosine
A 52-year- old male sought medical help complaining about progressive
appearance of hyperchromic (hyper pigmented) papules on the edge of the
second finger of both hands. He also complained about darkening of urine.
, Incisional biopsy of one of the spots on his hands and urine sample tested
positive for or homogentisic acid. Based on these findings a diagnosis of
alkaptonuria is made. This diagnosis is consistent with a deficiency in which of
the following enzymes?
Homogentisate oxidase
Which of the following compounds or substrates is required for the synthesis of
tyrosine? (+ indicates the compound is required; - indicates the compound is not
required)
(THF) (BH4) Tryptophan Phenylalanine
1. + + + -
2. - + + -
3. + - - +
4. - + - +
4
An individual is suspected of having a deficiency in branched chain keto acid
dehydrogenase. Supplementation of which of the following vitamins or cofactors
may help resolve this issue?
Thiamine
A 2-day-old infant test positive for hyperphenylalaninemia. This is most likely
caused by a heritable defect in which of the following enzymes?
Phenylalanine hydroxylase
A deficiency in B6 (pyridoxal phosphate) would negatively impact which of the
following pathways:
1. Metabolism of homocysteine to cysteine
2. Metabolism of phenylalanine to tyrosine
3. Conversion of methyl malonyl-CoA to succinyl-CoA
1 only
The ribonucleotide reductase is important for converting ribose bases to the
deoxy form. This conversion is coupled with the oxidation of which of the
following compounds?
Thioredoxin
A patient recently diagnosed with colon cancer is being treated with 5-
fluorouracil. Which of the following enzymes will this drug directly inhibit?
Thymidylate synthase
Purine biosynthesis starts with the activation of a 5-carbon sugar. In this initial
reaction, ribose 5-phosphate is converted into which of the following
compounds?
PRPP (5- phosphoribosylpyrophosphate)
In the salvage of purines, hypoxanthine-guanine phosphoribosyl transferase
(HGPRT) is responsible for which of the following processes?
Conversion of guanine to guanosine monophosphate (GMP)
