Tryptophan
| A | Thermoregulatory centre to shift to new level | |
| B | Resetting of skin temperature | |
| C | Both of the above | |
| D | None of the above |
| A | Thermoregulatory centre to shift to new level | |
| B | Resetting of skin temperature | |
| C | Both of the above | |
| D | None of the above |
Thermoregulatory centre to shift to new level
For each description, choose the neurotransmitter with which it is usually associated: Ingestion of l-tryptophan increases the levels of this substance in the brain.
| A |
Serotonin |
|
| B |
Norepinephrine |
|
| C |
Dopamine |
|
| D |
Acetylcholine |
For each description, choose the neurotransmitter with which it is usually associated: Ingestion of l-tryptophan increases the levels of this substance in the brain.
| A |
Serotonin |
|
| B |
Norepinephrine |
|
| C |
Dopamine |
|
| D |
Acetylcholine |
Maize contains the vitamin niacin. Pellagra is a disease that results from niacin deficiency.
Assertion: Consumption of maize may aggravate Pellagra.
Reason: Some strains of maize contains excess of Leucine which interferes in the conversion of Tryptophan into Niacin.
| A |
Both Assertion and Reason are true, and Reason is the correct explanation for Assertion |
|
| B |
Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion |
|
| C |
Assertion is true, but Reason is false |
|
| D |
Assertion is false, but Reason is true |
Maize contains the vitamin niacin. Pellagra is a disease that results from niacin deficiency.
Assertion: Consumption of maize may aggravate Pellagra.
Reason: Some strains of maize contains excess of Leucine which interferes in the conversion of Tryptophan into Niacin.
| A |
Both Assertion and Reason are true, and Reason is the correct explanation for Assertion |
|
| B |
Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion |
|
| C |
Assertion is true, but Reason is false |
|
| D |
Assertion is false, but Reason is true |
Pellagra is caused by Niacin deficiency and anything that interferes in the absorption or production of Niacin will aggravate the condition.
Which of the following is the 1st product of tryptophan catabolism?
| A |
Xantheurenate |
|
| B |
Kynurenine |
|
| C |
PAF |
|
| D |
Bradykinin |
Which of the following is the 1st product of tryptophan catabolism?
| A |
Xantheurenate |
|
| B |
Kynurenine |
|
| C |
PAF |
|
| D |
Bradykinin |
Tryptophan is degraded to amphibolic intermediates via the kynurenine-anthranilate pathway.
Tryptophan oxygenase converts tryptophan to N formyl kynurenine by opening the indole ring and by incorporating molecular oxygen.
This inturn is catalysed by kynurenine formylase to produce kynurenine.
Hartnup’s disease result from impaired intestinal and renal transport of tryptophan and other neutral amino acids.
This defect accounts for deficient niacin biosynthesis resulting in pellagra like signs and symptoms.
Ref: Harper’s Illustrated Biochemistry, 29e, Chapter 29
Melatonin, plays an important role in sleep-wake cycle, is secreted by:
| A |
Pineal gland |
|
| B |
Thyroid gland |
|
| C |
Ant. pituitary |
|
| D |
Pancreas |
Melatonin, plays an important role in sleep-wake cycle, is secreted by:
| A |
Pineal gland |
|
| B |
Thyroid gland |
|
| C |
Ant. pituitary |
|
| D |
Pancreas |
The following is false about Tryptophan
| A |
Non essential amino acid |
|
| B |
Involved in serotonin synthesis |
|
| C |
Involved in niacin synthesis |
|
| D |
Involved in melatonin synthesis |
The following is false about Tryptophan
| A |
Non essential amino acid |
|
| B |
Involved in serotonin synthesis |
|
| C |
Involved in niacin synthesis |
|
| D |
Involved in melatonin synthesis |
Melatonin is secreted by:
| A |
Hypothalamus |
|
| B |
Adrenal cortex |
|
| C |
Pineal gland |
|
| D |
Melanocytes |
Melatonin is secreted by:
| A |
Hypothalamus |
|
| B |
Adrenal cortex |
|
| C |
Pineal gland |
|
| D |
Melanocytes |
C i.e. Pineal gland
Melatonin is synthesized & secreted by pineal glandQ.
Exposure to darkness leads to increased melatonin secretion.
It is brought about by:
| A |
Decreasing the activity of suprachiasmatic nuclei |
|
| B |
Increasing the serotonin N-acetyl transferase |
|
| C |
Decreasing the hydroxy-indole-o-methyl transferase, activity |
|
| D |
Blocking the release of norepinephrine from sympathetic nerve terminals |
Exposure to darkness leads to increased melatonin secretion.
It is brought about by:
| A |
Decreasing the activity of suprachiasmatic nuclei |
|
| B |
Increasing the serotonin N-acetyl transferase |
|
| C |
Decreasing the hydroxy-indole-o-methyl transferase, activity |
|
| D |
Blocking the release of norepinephrine from sympathetic nerve terminals |
B i.e. Increasing the serotonin N- acetyl transferase
Increased in N-acetyl transferase of hydroxy indole-o-methyl (HOM) transferase activity in darkness Vt increased melatonin secretionQ
One mg. of Niacin is produced by…………………….. mg. of Tryptophan-
| A |
22 |
|
| B |
37 |
|
| C |
55 |
|
| D |
60 |
One mg. of Niacin is produced by…………………….. mg. of Tryptophan-
| A |
22 |
|
| B |
37 |
|
| C |
55 |
|
| D |
60 |
Ans. is ‘d’ i.e., 60
About 60 mg of tryptophan is required to result in I mg of niacin.
Melatonin is associated with all of the following except:
March 2010
| A |
Vomiting |
|
| B |
Pituitary gland secretion |
|
| C |
Sleep mechanism |
|
| D |
Jetlag |
Melatonin is associated with all of the following except:
March 2010
| A |
Vomiting |
|
| B |
Pituitary gland secretion |
|
| C |
Sleep mechanism |
|
| D |
Jetlag |
Ans. A: Vomiting
Melatonin and the enzymes responsible for its synthesis from serotonin by N-acetylation and 0-methylation are present in pineal parenchymal cells, and the hormone is secreted by them into the blood and the cerebrospinal fluid. Melatonin synthesis and secretion are increased during the dark period of the day and maintained at a low level during the daylight hours. This remarkable diurnal variation in secretion is brought about by norepinephrine secreted by the postganglionic sympathetic nerves (nervi conarii) that innervate the pineal. The norepinephrine acts via -adrenergic receptors in the pineal to increase intracellular cAMP, and the cAMP in turn produces a marked increase in N-acetyltransferase activity. This results in increased melatonin synthesis and secretion.
Effects of Melatonin:
- It plays a role in sleep mechanism
- It is supposed to decrease gonadotropic hormone secretion by anterior pituitary
Vomiting centre is located in the brain stem. From here, motor impulses that cause the actual vomiting are transmitted from the vomiting center by the way of the 5th,7th,9th,10th and 12th cranial nerves to the upper GIT, through vagal and sympathetic nerves to the lower tract and through spinal nerves to the diaphragm and abdominal vessels.
Metabolism of which of the following amino acid is at fault in Hartnup’s disease:
| A |
Tryptophan |
|
| B |
Sulfur amino acids |
|
| C |
Glycine |
|
| D |
Histidine |
Metabolism of which of the following amino acid is at fault in Hartnup’s disease:
| A |
Tryptophan |
|
| B |
Sulfur amino acids |
|
| C |
Glycine |
|
| D |
Histidine |
Abnormal metabolism of amino acids and conditions
- Hartnup’s disease is a hereditary disorder of tryptophan metabolism
- Sulfur amino acids (methionine, cysteine and cystine) metabolism disorder results in cystinuria, cystinosis, homocystinuria and cystathionuria
- Disorder of glycine metabolism results in glycinuria and primary hyperoxaluria
- Defect in metabolism of histidine results in histidinemia
Hartnup’s disease is associated with increased urinary excretion of:
| A |
Tryptophan |
|
| B |
Ornithine |
|
| C |
Glycine |
|
| D |
Cystine |
Hartnup’s disease is associated with increased urinary excretion of:
| A |
Tryptophan |
|
| B |
Ornithine |
|
| C |
Glycine |
|
| D |
Cystine |
Hartnup’s disease is characterized by low plasma levels of tryptophan and other neutral amino acids and their elevated urinary excretion
Which of the following is found in urine in Hartnup’s disease patients?
| A |
Phenyalanine |
|
| B |
Ornithine |
|
| C |
Cystine |
|
| D |
None |
Which of the following is found in urine in Hartnup’s disease patients?
| A |
Phenyalanine |
|
| B |
Ornithine |
|
| C |
Cystine |
|
| D |
None |
Hartnup disease is inherited as an autosomal recessive trait.
Heterozygotes are normal. Consanguinity is common.
Which of the following is caused by defective transport of tryptophan?
| A |
Hartnup disease |
|
| B |
Maple syrup urine disease |
|
| C |
Alkaptonuria |
|
| D |
Phenylketonuria |
Which of the following is caused by defective transport of tryptophan?
| A |
Hartnup disease |
|
| B |
Maple syrup urine disease |
|
| C |
Alkaptonuria |
|
| D |
Phenylketonuria |
Hartnup disease
- It is an inherited disorder in the metabolism of tryptophan.
- It is due to defective transport of tryptophan and other neutral amino acids in the intestine and kidney.
- This results in deficiency of tryptophan leading to decreased synthesis of niacin and serotonin.
- Thus there are pellagra (niacin deficiency), neurological symptoms (serotonin deficiency) and amino aciduria due to defective transport of amino acids in kidney.
In pyridoxine deficiency, tryptophan is converted to ‑
| A |
Nicotine |
|
| B |
Acetoacetate |
|
| C |
Xantheurenic acid |
|
| D |
Acetyl CoA |
In pyridoxine deficiency, tryptophan is converted to ‑
| A |
Nicotine |
|
| B |
Acetoacetate |
|
| C |
Xantheurenic acid |
|
| D |
Acetyl CoA |
Ans. is ‘c’ i.e., Xantheurenic acid
Hartnup disease is related to ‑
| A |
Rickets symptoms |
|
| B |
Pellagra symptoms |
|
| C |
Burning foot syndrome |
|
| D |
Angular stomatitis |
Hartnup disease is related to ‑
| A |
Rickets symptoms |
|
| B |
Pellagra symptoms |
|
| C |
Burning foot syndrome |
|
| D |
Angular stomatitis |
Hartnup disease
It is an inherited disorder in the metabolism of tryptophan.
It is due to defective transport of tryptophan and other neutral amino acids in the intestine and kidney.
This results in deficiency of tryptophan leading to decreased synthesis of niacin and serotonin.
Thus there are pellagra (niacin deficiency), neurological symptoms (serotonin deficiency) and amino aciduria due to defective transport of amino acids in kidney.
Tryptophan is glucogenic & ketogenic by producing
| A |
Acetyl CoA & alanine |
|
| B |
Acetoacetate & fumarate |
|
| C |
Acetoacetate & arginine |
|
| D |
Arginine & alanine |
Tryptophan is glucogenic & ketogenic by producing
| A |
Acetyl CoA & alanine |
|
| B |
Acetoacetate & fumarate |
|
| C |
Acetoacetate & arginine |
|
| D |
Arginine & alanine |
Ans. is ‘a’ i.e., Acetyl CoA & alanine
Melatonin is derived from ‑
| A |
Tyrosine |
|
| B |
Tryptophan |
|
| C |
Glutathione |
|
| D |
None |
Melatonin is derived from ‑
| A |
Tyrosine |
|
| B |
Tryptophan |
|
| C |
Glutathione |
|
| D |
None |
Ans. is ‘b’ i.e., Tryptophan
