If D 3, the product of the isomerization, becomes overconcentrated, the reaction may be forced into equilibrium, stopping vitamin D 3 synthesis. To keep the reaction going, a protein -the descriptively named vitamin D binding protein -binds to the newly created vitamin D 3 and transports it into the blood, via capillaries located where the epidermis meets the lower skin layer, the dermis. The final stage, isomerization, or converting preD 3 into vitamin D 3 is dependent on the temperature within the skin. Ultraviolet B radiation (wavelength 280-315 nanometers) penetrates through the skin, converting 7-DHC into an isomer -same chemical formula, but different spatial configuration of atoms -of vitamin D 3 called preD 3. Vitamin D synthesis begins with 7-dehydrocholesterol (7-DHC), a molecule present throughout the skin but most highly concentrated in the lowest layers of the epidermis, the stratum basale and especially the stratum spinosum. Holick and colleagues that used rat skin as a model for human skin. The process was first detailed in a 1980 study by M. While vitamin D 3 can be obtained through diet, the human body synthesizes it through exposure to sunlight. Its absence leads to a variety of ailments, most notably the bent limbs and weak bones characteristic of rickets.
Vitamin D 3 is essential to human health.
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