7-Dehydrocholesterol is the precursor of cholecalciferol.
2.
Provitamin D 2 is ergosterol, and provitamin D 3 is 7-dehydrocholesterol.
3.
The first step involves a photochemically induced conrotatory ring opening of 7-dehydrocholesterol to form pre vitamin D3.
4.
Vitamin D 3 is produced photochemically from 7-dehydrocholesterol in the skin of most vertebrate animals, including humans.
5.
In animals C5SD catalyzes the dehydration of lathosterol to 7-dehydrocholesterol, a step in the synthesis of cholesterol.
6.
In 1935, the chemical structure of vitamin D 3 was established and proven to result from the ultraviolet irradiation of 7-dehydrocholesterol.
7.
At that time there was no synthetic vitamin D, but the dehydrocholesterol in milk can be converted to vitamin D by radiation with ultraviolet light.
8.
Desmosterol is the immediate precursor of cholesterol in the Bloch pathway of cholesterol biosynthesis . 24-dehydrocholesterol reductase catalyses the reduction of desmosterol to cholesterol.
9.
:: : : : : : Historically, food only contained the precursor, 7-dehydrocholesterol, which then required exposure to UV light to form vitamin D 3.
10.
The vitamin D in milk comes either from the cow's milk itself ( the cow also makes cholecalciferol in its skin through the UV activation of 7-dehydrocholesterol ) or from the fortification of the milk with cholecalciferol.
मोबाइल