Category: Metabolism of Amino acids

trial 4 0

Phenylalanine – a source of energy and precursor of neurotransmitters

A 27- year-old semi professional tennis player seeks advice from a hospital -based nutritionist concerning his diet supplements. His coach had given him amino acid supplements consisting of phenylalanine 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. Phenylalanine upon metabolism, enter TCA cycle as which of the following? A) Oxaloacetate B) Citrate C) Succinyl Co A D) Fumarate E) α- Ketoglutarate The correct answer is- Fumarate. Phenylalanine is both glucogenic as well as...

trial 4 2

Histidine to histamine conversion

Histamine causes vasodilatation and bronchoconstriction. In the stomach it stimulates the secretion of hydrochloric acid (HCl). Histamine binds to H1 receptors in the stomach, stimulating the release of gastric acid. Pharmacological blockers of H1 receptors are used in the treatment of gastric reflux. H2 receptors are located on basophils; histamine stimulates their degranulation during the allergic responses. H2 receptor blockers are used to treat allergic conditions. Histamine is produced from Histidine by: A. Deamination B. Transamination C. Carboxylation D. Decarboxylation E. Methylation The correct answer is D- Decarboxylation. Histamine is a biogenic amine. A biogenic amine is a potent signaling...

trial 4 0

Significance of Glycine

Glycine functions as an inhibitory neurotransmitter in the brain stem and the spinal cord. Its actions are antagonized by the rodenticide Strychnine, leading to twitching and muscle spasm. The non availability of glycine can affect the synthesis of which of the following compounds? A. Methionine B. Hippuric acid C. Glucuronic acid D. Cysteine E. Mercapturic acid. Details The correct answer is- B- Hippuric acid Aromatic compounds like benzoic acid obtained from diet are detoxified by conjugation with glycine to form Hippuric acid (figure-1) which is excreted in urine.  This reaction takes place exclusively in liver. Hippuric acid excretion test is...

trial 4 0

Case study- Hyperammonemia

Question of the day -Hyperammonemia A new-born becomes progressively lethargic after feeding. His respiratory rate increases and he becomes virtually comatose, responding only to painful stimuli, and exhibits mild respiratory alkalosis. Suspicion of a urea cycle disorder is aroused and evaluation of serum amino acid levels is initiated. In the presence of hyperammonemia, production of which of the following amino acids is always increased? A. Glycine B. Arginine C. Proline D. Histidine E. Glutamine Answer- The correct answer is Glutamine. Urea cycle disorder results in reduced ammonia disposal and hence the patients present with symptoms of hyperammonemia. Ammonia is detoxified by...

trial 4 0

A common intermediate of Urea and TCA cycle

Question of the day Which one of the following can be converted to an intermediate of either the citric acid cycle or urea cycle? A. Tyrosine B. Lysine C. Leucine D. Tryptophan E. Aspartate Answer- The correct answer is- E -Aspartate. 1) Role of Aspartate in urea cycle Aspartate participates in urea cycle for condensation with citrulline to form Argino succinic acid. The reaction is catalyzed by Argino succinic acid synthetase (Aspartate provides one out of the two nitrogens of urea, the other nitrogen is contributed by Glutamate). In the subsequent reaction, Argino succinic acid undergoes a lytic reaction to...

trial 4 0

Which amino acid is both glucogenic as well as ketogenic ?

A 54-year-old male who was diagnosed with HIV (human immuno deficiency virus) infection 2 years back, is currently in the terminal stage. He is now cachectic and having a difficult time obtaining any caloric intake yet he refuses to take a naso gastric or gastric feeding tube. Since his muscle and organs are metabolically active, which of the following amino acids will produce both glucose and ketone bodies as an energy source? A. Alanine B. Tyrosine C. Proline D. Glycine E. Leucine The correct answer is B- Tyrosine. Amino acids can be classified based on their metabolic fate- I) Purely...

trial 4 0

Liver cirrhosis and ammonia intoxication

Case details A 55-year-old man suffers from cirrhosis of liver. Toxins such as ammonia are not properly metabolized by the liver in this disease and can damage the organs such as brain. Which of the following amino acids covalently binds ammonia, transports and stores it in a non toxic form? A. Tryptophan B. Alanine C. Aspartate D. Glutamate E. Glutamine The correct answer is- D- Glutamate. Glutamate occupies a central place in the amino acid metabolism. Basically it acts as a collector of amino group of the amino acids. Free ammonia is toxic to the body especially to brain cells;...

trial 4 0

Medication that acts by activating c GMP ?

Case details A 50-year-old male is brought to the emergency room with chest pain and shortness of breath. He is given a medication that activates cGMP, resulting in relaxation of vascular smooth muscle. This medication is most likely a derivative of: A. Creatine phosphate B. S-Adenosyl Methionine C. Glutathione D. Melatonin E. Nitric oxide Answer- E- Nitric oxide Nitric oxide is a highly reactive gas. It participates in many chemical reactions. Endothelium-derived relaxing factor was originally the name given to several proposed factors causing vasodilatation. The major endothelial derived relaxing factor was later discovered to be nitric oxide (NO). Nitric...

trial 4 0

Phenylketonuria- A case report

Case details A newborn male infant was diagnosed as having phenylketonuria (PKU), and immediately placed on diet low in phenylalanine ; careful compliance with the diet and frequent monitoring of the patient’s plasma Phenyl alanine level resulted in the level being maintained at the lower limit of the normal range. The patient appeared to be developing normally until 4 months of age, when he developed truncal hypotonia and spasticity of the limbs. Despite being on a low-phenylalanine diet, at 5 months the patient had several grand mal (epileptic) seizures. After an abnormal Phenyl alanine-loading test, the patient’s urine was found to...

trial 4 0

Answer- Case study- Epilepsy

Question of the day A 12-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 the amino acid glutamate via which of the following biochemical reactions? A. Deamination B. Decarboxylation C. Hydroxylation D. Iodination E. Methylation Answer- The correct answer is B- Decarboxylation, Glutamic acid undergoes decarboxylation to yield GABA. The reaction is catalyzed by Glutamic acid decarboxylase that requires vitamin B6-P as a coenzyme. GABA is an inhibitory neurotransmitter and is thus helpful in controlling convulsions. Deamination...

trial 4 3

Case study- Epilepsy-A 12-year-old boy develops convulsions..

Question of the day A 12-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 the amino acid glutamate via which of the following biochemical reactions ? A. Deamination B. Decarboxylation C. Hydroxylation D. Iodination E. Methylation Figure- Benzodiazepines  bind to the gamma sub-unit of the GABA-A receptor. Their binding causes an allosteric (structural) modification of the receptor that results in an increase in GABA A receptor activity. Benzodiazepines do not substitute for GABA, which bind at the...

trial 4 0

Answer to the question- Amino acids in the post absorptive state ..

During a medical rotation, a medical student volunteered for a respiratory physiology exam 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 serum? A. Alanine and Glutamine B. Arginine and Ornithine C. Glutamate and Aspartate D. Branched chain amino acids E. Hydrophobic amino acids Answer- A- Alanine and Glutamine. Post absorptive state is the state of the body 3-5 hours after meals. It is that period of time in the body during which...

trial 4 2

Amino acids in the post absorptive state ?

Question of the day During a medical rotation, a medical student volunteered for a respiratory physiology exam 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 serum? A. Alanine and Glutamine B. Arginine and Ornithine C. Glutamate and Aspartate D. Branched chain amino acids E. Hydrophobic amino acids   Figure- Post absorptive state For answer follow the link http://usmle.biochemistryformedics.com/answer-to-the-question-amino-acids-in-the-post-absorptive-state/ Please help Biochemistry for Medics by “CLICKING ON THE ADVERTISEMENTS” every time you visit...

trial 4 0

Answer- Case study- Hyperammonemia and orotic aciduria

A newborn becomes lethargic and drowsy 24 hour after birth. Blood analysis shows hyperammonemia, coupled with Orotic aciduria. This individual has an enzyme deficiency that leads to an inability to directly produce which of the following? A. Carbamoyl phosphate B. Ornithine C. Citrulline D. Argininosuccinate E. Arginine Answer- The correct answer is -C-Citrulline. Orotic aciduria refers to an excessive excretion of Orotic acid in urine. This is a disorder of pathway of pyrimidine biosynthesis inherited in an autosomal recessive manner. Increased excretion of orotic acid, uracil, and uridine also accompanies a deficiency in liver mitochondrial ornithine transcarbamoylase, an enzyme of...

trial 4 2

Case study- Hyperammonemia and Orotic aciduria

Question of the day A newborn becomes lethargic and drowsy 24 hour after birth. Blood analysis shows hyperammonemia, coupled with Orotic aciduria. This individual has an enzyme deficiency that leads to an inability to directly produce which of the following? A. Carbamoyl phosphate B. Ornithine C. Citrulline D. Argininosuccinate E. Arginine   Figure- Structure of Orotic acid For answer follow the link http://usmle.biochemistryformedics.com/answer-case-study-hyperammonemia-and-orotic-aciduria/ Please help Biochemistry for Medics by “CLICKING ON THE ADVERTISEMENTS” every time you visit us. Thank you!

trial 4 0

Answer- Case study- Oral contraceptives induced vitamin deficiencies

Case Details Oral contraceptives are known to lower blood levels of folate and vitamin B6. Which of the following conversion processes might be directly affected? A. Ornithine to Citrulline B. Histidine to histamine C. Glutamate to Glutamine D. Propionyl co A to Methyl malonyl co A E. Phenyl alanine to Tyrosine Answer- B- The correct answer is conversion of Histidine to histamine. The reaction is catalyzed by decarboxylase that requires B6-P as a cofactor (Figure-1) that gets deficient in women upon long-term oral contraceptive usage. Folic acid is not required in this reaction. Figure-1- Decarboxylation of Histidine is carried out...

trial 4 1

Case- Oral contraceptive induced Vitamin deficiencies

Question of the day Oral contraceptives are known to lower blood levels of folate and vitamin B6. Figure- Oral contraceptives Which of the following conversion processes might be directly affected ? A. Ornithine to Citrulline B. Histidine to histamine C. Glutamate to Glutamine D. Propionyl co A to Methyl malonyl co A E. Phenyl alanine to Tyrosine For answer follow the link http://usmle.biochemistryformedics.com/answer-case-study-oral-contraceptives-induced-vitamin-deficiencies/ Please help Biochemistry for Medics by “CLICKING ON THE ADVERTISEMENTS” every time you visit us. Thank you!

trial 4 0

Answer- Case study- Urea cycle disorder

Case details A 2-year-old girl was seen in the emergency room for vomiting and tremors. The elevated plasma ammonium ion concentration was 200 μM/L (normal 11-40 μM/L). Metabolic screens of blood and serum were ordered and were remarkable for an elevation in the amino acid arginine in serum. Which of the following enzymes would most likely cause an elevation in the plasma Arginine levels? A. Carbamoyl phosphate synthetase I B. Carbamoyl phosphate synthetase II C. Ornithine transcarbamoylase D. Arginase E. Argino succinate lyase Answer- The correct answer is D- Arginase Arginine is an intermediate of urea cycle. Its high concentration...

trial 4 1

Case study- Ammonia Intoxication-A 2-year-old girl was seen in the emergency room ..

Question of the day A 2-year-old girl was seen in the emergency room for vomiting and tremors. The elevated plasma ammonium ion concentration was 200 μM/L (normal 11-40 μM/L). Metabolic screens of blood and serum were ordered and were remarkable for an elevation in the amino acid arginine in serum. Which of the following enzymes would most likely cause an elevation in the plasma Arginine levels? A. Carbamoyl phosphate synthetase I B. Carbamoyl phosphate synthetase II C. Ornithine transcarbamoylase D. Arginase E. Argino succinic acid lyase Figure- Structure of Arginine For answer follow the link http://usmle.biochemistryformedics.com/answer-case-study-urea-cycle-disorder/ Please help Biochemistry for...

trial 4 0

Answer- Case study- Amino acid supplements- A 27- year-old, semiprofessional tennis player seeks advice from a hospital-based nutritionist…

AMINO ACID METABOLISM 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 enters TCA cycle as which of the following? A. Oxaloacetate B. Fumarate C. Succinyl co A D. Citrate E. α- Keto glutarate Answer- The right answer is B- Fumarate. Phenyl...

trial 4 1

Case study- Amino acid supplements-A 27- year-old, semiprofessional tennis player seeks advice from a hospital-based nutritionist concerning his diet…

QUESTION OF THE DAY AMINO ACID METABOLISM 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. Figure- Amino acid supplements In reality, the excess amino acids are used for energy, with a poor and eclectic diet. Phenyl alanine upon metabolism enters TCA cycle as which of the following? A. Oxaloacetate B. Fumarate C. Succinyl co A D. Citrate E. α- Keto glutarate...

Copy Protected by Chetan's WP-Copyprotect.