Final answer:
The vitamin precursor for Cholecalciferol (D3) is 7-dehydrocholesterol, which is converted to vitamin D3 when skin is exposed to sunlight. Vitamin D is essential for the normal absorption of calcium and phosphorous, which are needed for healthy bones. It can be obtained from sun exposure or through dietary supplements added to certain foods.
Step-by-step explanation:
The vitamin precursor for Cholecalciferol (D3) is 7-dehydrocholesterol. This precursor is found in the epidermal layer of our skin. When exposed to UV radiation from sunlight, 7-dehydrocholesterol is converted into cholecalciferol (vitamin D3). The liver further metabolizes cholecalciferol into 25-hydroxycholecalciferol (calcidiol), which is then converted in the kidneys to the biologically active form of vitamin D, called calcitriol.