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Solved MCQs of Amino Acid Metabolism for 2nd Year MBBS

 Multiple Choice Questions (Solved)- Amino acid Metabolism


Multiple Choice Questions (Solved)- Amino acid Metabolism( answers are given at the end of the questions )

Q.1- A 10 -year-old boy develops convulsions. After running an Electroencephalogram(EEG), a neurologist determines that the child has epilepsy. He is started on benzodiazepine which promotes the activity of GABA. GABA is derived from Glutamate by which of the following reactions ?

  1. a) Transamination
  2. b) Decarboxylation
  3. c) Deamination
  4. d) Hydroxylation
  5. e) Dehydrogenation

Q.2- A couple of African- American descent gives birth to a boy  after an otherwise uneventful pregnancy. The child is exceptionally fair skinned and has almost white hair. Further examination reveals red pupils.  A postnatal screen is likely to confirm the deficiency of which of the following enzymes ?

  1. a) Glutathione reductase
  2. b) Glutathione peroxidase
  3. c) Tyrosinase
  4. d) Methionine synthase
  5. e) Cystathionine beta synthase

Q.3- A 16- year -old girl is found by her parents unconscious on the bathroom floor with an empty bottle of acetaminophen in the toilet. She is rushed to the hospital where she is given several doses of N-acetyl Cysteine. Acetaminophen overdose is potentially life threatening because it depletes the cellular stores of Glutathione. Which of the following amino acid is another component of Glutathione besides Cysteine and Glutamic acid ?

  1. a) Methionine
  2. b) Arginine
  3. c) Lysine
  4. d) Ornithine
  5. e) Glycine

Q.4-  A 56- year-old man with  long-standing poorly controlled diabetes mellitus visits his primary care physician for a follow-up after a recent hospitalization. The patient experienced an episode of acute renal failure while in hospital and his serum creatinine rose to 2.4 mg/dl ( Normal, 0.7- 1.5 mg/dl). Creatinine, a marker of kidney function, is derived from which of the following precursors ?

  1. a) Arginine, Lysine and Glutamine
  2. b) Glutamic acid, Cysteine and Glycine
  3. c) Methionine, Serine and Glycine
  4. d) Methionine, Arginine and Glycine
  5. e) Cysteine, Glycine and Arginine.

Q.5- S- Adenosyl  Methionine (Active Methionine) is required for the synthesis  of which of the following compounds ?

  1. a) Thyroid hormone
  2. b) Melanin
  3. c) Epinephrine
  4. d) Serotonin
  5. e) Bile salts.

Q.6- Which of the following compounds is formed from  hydroxylation requiring vitamin C and subsequent methylation ?

  1. a) Histamine
  2. b) Dopamine
  3. c) Epinephrine
  4. d) Creatine
  5. e) Melanin

Q.7- A 40-year old woman complains of deceased energy, significant weight gain and cold intolerance. She is seen by her family physician, who has diagnosed her to be having hypothyroidism (Low  level of thyroid hormone). Which of the following is a precursor for thyroid hormone ?

  1. a)  DOPA
  2. b) Glutamine
  3. c)  Tyrosine
  4. d) Tryptophan
  5. e) Threonine.

Q.8- A 63 -year old woman reports a long history of joint pains. Her fingers are severely deformed secondary to rheumatoid arthritis. Upon visiting a rheumatologist, she is started on methotrexate. This drug inhibits which of the following conversions ?

Dopamine to norepinephrine conversion

Tyrosine to Dopa

Dihydrofolate to Tetra hydro folate

Phenyl Alanine to Tyrosine

N-Acetyl serotonin to melatonin

Q.9-  A 59-year-old woman develops a shuffling gait and a pin- rolling tremor. She is referred to a neurologist for evaluation. After a thorough workup, a diagnosis of Parkinson disease is made and the patient is placed on Mono amine oxidase inhibitor. The drug in this case, is given to decrease the degradation of which of the followings ?

  1. a) Serotonin
  2. b) Dopamine
  3. c) Nicotinamide
  4. d) Melatonin
  5. e) Nitric oxide

Q.10- During a medical rotation, a medical student volunteered for a respiratory physiology examination that determines basal metabolic rate and the respiratory quotient. She followed the protocol for a resting individual in the post absorptive state. Which of the following amino acids would be found in the highest concentration in the serum ?

  1. a) Alanine and Glutamine
  2. b) Arginine and Ornithine
  3. c) Glutamate and Aspartate
  4. d)  Branched chain amino acids
  5. e) Hydrophobic amino acids

Q.11- A 27- year-old semiprofessional  tennis player seeks advice from a hospital -based nutritionist concerning his diet supplements. His coach had given him amino acid supplements consisting of phenyl alanine and tyrosine. The rationale was that these precursors to several neurotransmitters will “help his brain focus” on his game. In reality, the excess amino acids are used for energy, with a poor and eclectic diet. Phenyl Alanine upon metabolism, enter TCA cycle as which of the following ?

  1. a) Oxalo acetate
  2. b) Citrate
  3. c) Succinyl co A
  4. d) Fumarate
  5. e) α- Keto glutarate

Q.12- In a 39-year-old woman who just gave birth, chorionic villus sampling was performed, and a battery of genetic panels was assessed on the new-born. One marker indicated a defective Cystathionine -β- Synthase. Which of the following compounds you most likely expect to be elevated  in the blood of the infant at birth if the mother was not treated properly ?

  1. a) Valine
  2. b) Homocysteine
  3. c) Threonine
  4. d) Glutamine
  5. e) Cysteine

Q.13- A 55-year-old man suffers from cirrhosis of liver. Toxins such as ammonia are not properly metabolized by the liver and can damage brain. Which of the following compounds is expected to be in highest concentration in brain  as a result of detoxification of ammonia?

  1. a) Alpha keto glutarate
  2. b) Glutamate
  3. c)  Glutamine
  4. d) GABA
  5. e) Asparagine

Q.14- Which of the following enzymes requires adenosine triphosphate (ATP) to mediate its reactions ?

  1. a) Argino Succinate lyase
  2. b) Argino Succinate synthetase
  3. c) Arginase
  4. d) Glutaminase
  5. e) Ornithine transcarbamoylase

Q.15- Which of the following amino acids is not converted to Acetyl co A upon metabolism ?

  1. a) Tyrosine
  2. b) Leucine
  3. c) Tryptophan
  4. d) Lysine
  5. e) Valine



Key to Answers-

1)-b,      2)-c,      3)-e,      4)- d,     5)- c,      6)-c,       7)-c,       8)-c,       9)-b,      10)-a,    11)- d,   12-b,     13)-C

14)-b,    15)-e

Q.1- Which of the following is a common compound shared by the TCA cycle and the Urea cycle?

  1. a) α- Keto glutarate
  2. b) Succinyl co A
  3. c) Oxalo acetate
  4. d) Fumarate

Q.2-Which of the followings is a common nitrogen acceptor for all reactions involving transaminases?

  1. a) α- Keto glutarate
  2. b) Pyruvate
  3. c) Oxaloacetate
  4. d) Acetoacetate

Q.3- In a 55- year-old man, who has been diagnosed with cirrhosis of liver, Ammonia is not getting detoxified and can damage brain. Which of the following amino acids can covalently bind ammonia, transport and store in a non toxic form?

  1. a) Aspartate
  2. b) Glutamate
  3. c) Serine
  4. d) Cysteine

Q.4- In a new born presenting with refusal to feeds and irritability, a deficiency of Cystathionine –β- synthase has been diagnosed, which of the following compounds is expected to be elevated in blood?

  1. a) Serine
  2. b) Glutamate
  3. c) Homocysteine
  4. d) Valine

Q.5 -A 3- month-old child is being evaluated for vomiting and an episode of convulsions, Laboratory results show hyperammonemia and Orotic aciduria. Which of the following enzyme defect is likely to be there?

  1. a) Glutaminase
  2. b) Arginase
  3. c) Argino succinic acid synthase
  4. d) Ornithine Transcarbamoylase

Q.6- Which out of the following amino acids is not converted to Succinyl co A?

  1. a) Methionine
  2. b) Valine
  3. c) Isoleucine
  4. d) Histidine

Q.7-All of the following compounds are synthesized by transmethylation reactions, except-

  1. a) Choline
  2. b) Epinephrine
  3. c) Creatine
  4. d) Ethanolamine

Q.8- A patient diagnosed with Hart Nup disease, (due to deficiency of transporter required for the absorption of amino acid tryptophan), has been brought with skin rashes and suicidal tendencies. Tryptophan is a precursor for many compounds, the deficiencies of which can cause the said symptoms. Which out of the following compounds is not synthesized by tryptophan?

  1. a) Serotonin
  2. b) Epinephrine
  3. c) Melatonin
  4. d) Niacin

Q.9- Histamine, a chemical mediator of allergies and anaphylaxis, is synthesized from amino acid Histidine by which of the following processes?

  1. a) Deamination
  2. b) Decarboxylation
  3. c) Transamination
  4. d) Dehydrogenation

Q.10- The synthesis of all of the following compounds except one is deficient in a patient suffering from Phenylketonuria-

  1. a) Melanin
  2. b) Melatonin
  3. c) Catecholamines
  4. d) Thyroid hormone

Q.11- The diet of a child suffering from Maple syrup urine disease (an amino acid disorder), should be low, in which out of the following amino acids content?

  1. a) Branched chain amino acids
  2. b) Phenylalanine Alanine
  3. c) Methionine
  4. d) Tryptophan

Q.12- Which out of the following amino acids in not required for creatine synthesis?

  1. a) Methionine
  2. b) Serine
  3. c) Glycine
  4. d) Arginine

Q.13- All of the following substances are synthesized from Cysteine, except-

  1. a) Taurine
  2. b) Mercaptoethanolamine
  3. c) Melanin
  4. d) Pyruvate

Q.14- Urea is synthesized in –

  1. a) Cytoplasm
  2. b) Mitochondria
  3. c) Both cytoplasm and mitochondria
  4. d) In lysosomes

Q.15-Blood urea decreases in all of the following conditions, except-

  1. a) Liver cirrhosis
  2. b) Pregnancy
  3. c) Renal failure
  4. d) Urea cycle disorders

Q.16- All of the following amino acids are donors of one carbon compounds except-

  1. a) Histidine
  2. b) Tyrosine
  3. c) Tryptophan
  4. d) Serine

Q.17- The two nitrogen of urea are derived from-

  1. a) Aspartate and Ammonia
  2. b) Glutamate and ammonia
  3. c) Argino succinate and ammonia
  4. d) Alanine and ammonia

Q.18- Which out of the following amino acids is not required for the synthesis of Glutathione?

  1. a) Serine
  2. b) Cysteine
  3. c) Glutamic acid
  4. d) Glycine

Q.19- The first line of defence in brain in conditions of hyperammonemia is-

  1. a) Urea formation
  2. b) Glutamine synthesis
  3. c) Glutamate synthesis
  4. d) Asparagine formation

Q.20- Which coenzyme out of the followings is required for the oxidative deamination of most of amino acids?

  1. a) Folic acid
  2. b) Pyridoxal- P
  3. c) FMN
  4. d) FAD

Q.21-Chose the incorrect statement about amino acid Glycine-

  1. a) One carbon donor
  2. b) Required for the synthesis of haem
  3. c) Forms oxalates upon catabolism
  4. d) Both glucogenic as well as ketogenic

Q.22- Which out of the followings is required as a coenzyme for the transamination reactions?

  1. a) Coenzyme A
  2. b) Pyridoxal-P
  3. c) Folic acid
  4. d) Cobalamine

Q.23- A patient diagnosed with Homocystinuria should be supplemented with all of the following vitamins except-

  1. a) Vitamin C
  2. b) Folic acid
  3. c) Vitamin B12
  4. d) Pyridoxal- P

Q.24- In a patient suffering from Cystinuria, which out of the following amino acids is not seen in urine of affected patients?

  1. a) Arginine
  2. b) Methionine
  3. c) Lysine
  4. d) Ornithine

Q.25- Positive nitrogen balance is seen in all of the following conditions except-

  1. a) Pregnancy
  2. b) Growth
  3. c) Fever
  4. d) Convalescence

Q.26- The L-amino acids are absorbed from intestine by-

  1. a) Active transport
  2. b) Passive diffusion
  3. c) Pinocytosis
  4. d) Facilitated diffusion

Q.27- A child presented with increased frequency of urination, photophobia and impairment of vision. Which out of the following defects could be responsible for the said symptoms?

  1. a) Tyrosinosis
  2. b) Cystinosis
  3. c) Alkaptonuria
  4. d) Albinism

Q.28- Which out of the following statements about Glutamate dehydrogenase is correct?

  1. a) Required for transamination reactions
  2. b) Universally present in all the cells of the body
  3. c) Can utilize either of NAD+/NADP+
  4. d) Catalyzes conversion of glutamate to glutamine

Q.-29-A child was brought to paediatric OPD with complaint of passage of black colored urine. A disorder of Phenylalanine metabolism was diagnosed. A low phenylalanine diet and a supplementation of vitamin C were recommended. Which enzyme defect is expected in this child?

  1. a) Phenyl alanine hydroxylase
  2. b) Tyrosine transaminase
  3. c) Homogentisic acid oxidase
  4. d) Hydrolase

Q.30- Dopamine is synthesized from which of the following amino acids?

  1. a) Tyrosine
  2. b) Tryptophan
  3. c) Histidine
  4. d) Methionine

Q.31- In mammalian tissue serine can be a biosynthetic precursor for which amino acid?

  1. a) Methionine
  2. b) Glycine
  3. c) Arginine
  4. d) Lysine

Q.32- Hydroxylation of Phenyl Alanine to Tyrosine requires all except

  1. a) Glutathione
  2. b) Tetra hydrobiopterin
  3. c) Molecular oxygen
  4. d) NADPH

Q.33- The amino acid that undergoes oxidative deamination at a highest rate is-

  1. a) Glutamine
  2. b) Glutamate
  3. c) Aspartate
  4. d) Alanine

Q.34- All of the following statements regarding serotonin are true except-

  1. a) Causes vasodilatation
  2. b) Causes broncho constriction
  3. c) Metabolized to 5-hydroxy Indole acetic acid
  4. d) Causes diarrhoea

Q.35- Choose the incorrect statement about cysteine-

  1. a) Carbon skeleton is provided by serine
  2. b) Sulfur group is provided by Methionine
  3. c) Forms Hippuric acid for detoxification of xenobiotics
  4. d) Required for Bile salt formation



1) – d, 2) – a, 3) – b, 4) -c, 5) – d, 6) – d, 7) – d, 8) – b, 9) – b, 10) – b, 11) – a), 12) – b, 13) – c, 14) – c, 15) – c,16) – b, 17) – a, 18) – a,

19) – b, 20) – c, 21) – d, 22) – b,23) -a, 24)- b, 25) – c, 26) – a, 27) – b, 28) – c, 29) – c, 30) – a, 31) – b,32) – a, 33) – b, 34) – a,35) – c.