(1)Why does the consumption of excessive amounts of vitamins D and A cause adver
ID: 63067 • Letter: #
Question
(1)Why does the consumption of excessive amounts of vitamins D and A cause adverse health effects, whereas consumption of vitamin C well in excess of the recommended daily allowance generally not lead to toxicity?
(2)Spicy Indian dishes flavored with hot peppers (e.g. ghost peppers) are often served with a side dish made from whole-milk yogurt. Why is a spoonful of yogurt preferable to a drink of water after a mouthful of spicy food?
(3) In what way do nuclear receptors differ from cell surface receptors in their action after they have bound their cognate ligand?
Explanation / Answer
1) Vitamin A and D are fat soluble vitamins which can accumulate over time and lead to serious imbalances in physiological parameters which they control. Therefore they are toxic. On the other hand Vitamin C is water soluble which is rapidly cleared from the body and is non-toxic.
2) Spicy food contains capsaicinoids. These produce the sensation of pain by bonding with the pain receptors. Yoghurt acts like a grease which removes these capsaicinoids from the taste buds and provides instant relief.
3) After binding with their cognate ligand, the ligand-nuclear receptor complex migrates to the specific genomic loci and turns on the transcription of target genes. On the other hand cell surface receptor do not actually migrate but relay the signal to a second group of signaling molecules such as secondary messengers to bring about the desired effect.
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