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Renin Angiotensin Mechanism.

Synthesis and significance of biological substances: Serotonin, Melatonin, Catecholamines.

 

  1. Synthesis and Significance of 5-HT:

  • Also called “Serotonin”.

  • There are three main types of cells that store serotonin (5-hydroxytryptamine) -

    • Blood platelets

    • Neurons in the brain and the intestinal myenteric plexus,

    • Mucosa of the gastrointestinal tract contains enterochromaffin cells.

  • The enterochromaffin cells and serotonergic neurons produce serotonin from L-tryptophan, 

  • Platelets uptake the serotonin from blood.

  • In the cytosol of brain cells, the enzyme L-tryptophan hydroxylase (TPH) is involved in the synthesis of serotonin through the conversion of L-tryptophan to 5-hydroxytryptophan. 

  • Serotonin synthesis in neurons is regulated by this enzyme in a similar fashion to that by the related enzyme L-tyrosine hydroxylase, which converts L-tyrosine to L-dihydroxyphenylalanine (L-DOPA). 

  • Functions of Serotonin:

    • Mood elevator.

    • Involved in bone metabolism.

    • Involved in cardiovascular health.

    • Involved in eye health.

    • Involved in blood clotting.

    • Involved in neurological disorders.

  1. Melatonin:

  • Secreted by “Pineal Gland” and regulates sleep.

  • Secretion depends on light, secreted in dim light i.e. during night, effects are minimum during day.

  • Synthesized in the body from a similar pathway of Serotonin.

  • Functions:

    • Sleep quality and mood are improved. 

    • Melatonin functions can delay aging processes. 

    • Scavenging free radicals,

    • Stabilizing biological rhythms, 

    • Stimulates the immune system. 

    • Decreases susceptibility to stress.

  1. Catecholamines:

  • The substances containing catechol nuclei in their chemical structure are called “Catecholamines”.

  • Following are important catecholamines in the body,

    • Dopamine.

    • Adrenaline.

    • Noradrenaline.

  • Tyrosine is the precursor for the synthesis of catecholamines.

  • The conversion of tyrosine to catecholamines occurs in adrenal medulla and central nervous system.

  • Synthesis of Catecholamines:

  • Tyrosine is hydroxylated to 3,4-dihydroxyphenylalanine (DOPA) by tyrosine hydroxylase.  

  • This reaction requires tetra hydro biopterin as coenzyme.  

  • DOPA undergoes PLPdependent decarboxylation to give dopamine which, in turn, is hydroxylated to produce norepinephrine.  

  • Methylation of norepinephrine by S-adenosyl methionine gives epinephrine. 

  • The difference between epinephrine and norepinephrine is only a methyl group (norepinephrine has no methyl group).

  • Functions of catecholamines :

    • Norepinephrine and epinephrine regulate carbohydrate and lipid metabolisms.  

    • They stimulate the degradation of triacylglycerol and glycogen.  

    • They cause an increase in blood pressure.  

    • Dopamine and norepinephrine serve as neurotransmitters in the brain and autonomic nervous system.

    • Neurotransmitter dopamine plays a role in the brain. 

    • Striving, focusing, and finding something interesting rely on it.

    • It is associated with pleasure.

Commonly Asked Questions.

  1. Write about Synthesis and significance of Catecholamines in the body.

  2. Write about Synthesis and significance of Serotonin and Melatonin in the body.

  3. Give significance of Serotonin in the body.

  4. Give significance of Catecholamines in the body.

  5. Give significance of Melatonin in the body.
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