7-dehydrocholesterol
Structural formula | |||||||||||||||||||
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General | |||||||||||||||||||
Surname | 7-dehydrocholesterol | ||||||||||||||||||
other names |
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Molecular formula | C 27 H 44 O | ||||||||||||||||||
Brief description |
white solid |
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properties | |||||||||||||||||||
Molar mass | 384.34 g mol −1 | ||||||||||||||||||
Physical state |
firmly |
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Melting point |
148-152 ° C |
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safety instructions | |||||||||||||||||||
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
7-Dehydrocholesterol is a sterol which is the precursor to cholesterol and cholecalciferol (vitamin D 3 ). 7-dehydrocholesterol was discovered by the later Nobel Prize winner Adolf Windaus .
place
The skin is made up of two main layers. An inner layer, the dermis , and a thin, outer layer, the epidermis. The thickness of the epidermis is between 0.08 mm and 0.6 mm. The highest concentration of 7-dehydrocholesterol can be found in the epidermal layer, especially in the stratum spinosum and stratum basale . The production of previtamin D 3 is greatest between these two layers.
function
Formation of cholesterol
The enzyme 7-dehydrocholesterol reductase reduces 7-dehydrocholesterol to cholesterol .
In Smith-Lemli-Opitz syndrome, this enzyme is limited in its activity by various mutations. As a result, in this syndrome, the 7-dehydrocholesterol level in the blood is too high and the cholesterol level is too low. Cholesterol in turn serves as the starting substance for steroid hormones and bile acids .
Formation of vitamin D.
7-Dehydrocholesterol is first converted into previtamin D 3 by photolysis with UVB light of wavelengths 270-315 nm and then further converted into vitamin D 3 by thermal isomerization .
radiation
The synthesis of previtamin D 3 leads to the release of UVB radiation , which, however, practically only penetrates the epidermal layers of the skin. 7-Dehydrocholesterol absorbs UV light best between the wavelengths 290 nm and 320 nm, which is why the production of vitamin D 3 must take place between these wavelengths. The two most important factors for the generation of Previtamin D 3 are the quantity (intensity) and the quality (suitable wavelength).
Individual evidence
- ↑ a b c d data sheet 7-dehydrocholesterol from Sigma-Aldrich , accessed on June 15, 2011 ( PDF ).
- ^ F. Martini, MJ. Timmons: Human Anatomy . Ed .: Pearson / Benjamin-Cummings Publishers. 2006, ISBN 0-8053-7211-3 , pp. 89 .
- ↑ AW Norman: Sunlight, season, skin pigmentation, vitamin D, and 25-hydroxyvitamin D: integral components of the vitamin D endocrine system . In: The American Journal of Clinical Nutrition . tape 67 , no. 6 , June 1, 1998, ISSN 0002-9165 , p. 1108–1110 , doi : 10.1093 / ajcn / 67.6.1108 ( oup.com [accessed May 31, 2020]).
- ↑ Metabolism of vitamin D ( Memento from March 18, 2016 in the Internet Archive ).
- ↑ AW Norman: Sunlight, season, skin pigmentation, vitamin D, and 25-hydroxyvitamin D: integral components of the vitamin D endocrine system . In: The American Journal of Clinical Nutrition . tape 67 , no. 6 , June 1, 1998, ISSN 0002-9165 , p. 1108–1110 , doi : 10.1093 / ajcn / 67.6.1108 ( oup.com [accessed May 31, 2020]).