L9 biochem

Question 1

biological importance of tryptophan

Answer 1

1. conversion into niacin
2. precursor of NAD and NADP via synthesis of nicotinamide
3. precursor of serotonin, melatonin and tryptamine
4. enter in protein synthesis

Question 2

what is serotonin and where it is produced

Answer 2

monoamine neurotransmitter
in brain mast cell platelets and argentaffin cell

Question 3

describe synthesis of serotonin from tryptophan

Answer 3

tryptophan to 5-hydrotryptophan (hydroxylase + tetrahydrobiopterin)
5-hydrotryptophan to 5-hydroxytryptamine (decarboxylase + PLP)

Question 4

what is catabolic product of serotonin?

Answer 4

5-hydroxyindol-acetic acid (5-HIAA)

Question 5

what is clinical importance of 5-HIAA

Answer 5

increase in urine of patient with argentaffinoma (carcinoid syndrome )

Question 6

describe about argentaffinoma nand how it causes pellagra ?

Answer 6

argentaffin cell secrete serotonin for GIT motility.
malignant growth of this cells lead to formation of carcinoid tumor. this tumor may cause 60% of tryptophan will convert into serotonin instead of niacin. niacin deficiency occur cause pellagra (dementia, diarrhea, dermatitis)

Question 7

enumerate functions of serotonin?

Answer 7

-act as antidepressant
-has role in sleep, appetite and temperature regulation
- decrease sensitivity to pain it causes VC
-contraction of smooth muscle
-increase GIT motility

Question 8

what is melatonin and where it is produced?

Answer 8

-it is hormone of pineal body.
- it is secreted from pineal gland ( only secreted at night, its production inhibited by light )

Question 9

what are the function of melatonin?

Answer 9

-regulation of day night cycle (sleep)
-act as antioxidant

Question 10

describe effect of bacteria (putrifaction) on tryptophan in large intestine

Answer 10

they convert tryptophan into indole and skatole (putrefactive products of tryptophan). this product give odor to the stool. absorbed in liver conjugate with sulphate produce indoxyl sulphate and skatoxyle sulphate. conjugate with potassium ( potassium skatoxyle sulphate) in form of indican

Question 11

what is Hartnup disease

Answer 11

inherited autosomal recessive disease (defect in transport system of tryptophan)

Question 12

clinical manifestation of Hartnup disease

Answer 12

-pellagra
-cerebral ataxia (involuntary movement)
-mental retardation

Question 13

diagnosis of Hartnup disease

Answer 13

aminoaciduria (high level of amino acid in urine)
increase excretion of indole in urine

Question 14

what is the treatment of Hartnup disease

Answer 14

niacin