3d image of 7-dehydrocholesterol skeletal formula

7-dehydrocholesterol 7-dhc zoosterol cholesterol vitamin cholecalciferol synthesis sun metabolism skin calcitriol formation previtamin structural formula calcidiol reductase calcium ergocalciferol ergosterol light expression alfacalcidol agent paricalcitol lumisterol tocotrienol precursor 3d rendering chemical molecule molecular structure hormone hormonal function action steroid metabolite biosynthesis cycle mechanism intermediate biogenesis bioprecursor metabolic