7-dehydrocholesterol

7-Dehydrocholesterol is a sterol that serves as a precursor to vitamin D3 in the skin of animals and humans. It is a crucial component in the synthesis of vitamin D, which is essential for maintaining healthy bones and immune function.

Biological Role

7-Dehydrocholesterol is found in the skin, where it absorbs ultraviolet B (UVB) radiation from sunlight. This absorption leads to a photochemical reaction that converts 7-dehydrocholesterol into cholecalciferol, also known as vitamin D3. This process is vital for the production of vitamin D in the body, which is necessary for calcium absorption and bone health.

Chemical Structure

7-Dehydrocholesterol is a cholesterol derivative with the molecular formula C₂₇H₄₄O. It is characterized by a double bond between the 7th and 8th carbon atoms in the steroid ring structure, which distinguishes it from cholesterol.

Synthesis and Metabolism

In the skin, 7-dehydrocholesterol is synthesized from cholesterol through a series of enzymatic reactions. Upon exposure to UVB radiation, it undergoes a transformation to form pre-vitamin D3, which then spontaneously isomerizes to vitamin D3. This vitamin D3 is then transported to the liver and kidneys, where it is further metabolized into its active form, calcitriol.

Health Implications

Adequate levels of 7-dehydrocholesterol and subsequent vitamin D synthesis are crucial for preventing rickets in children and osteomalacia in adults. Deficiency in vitamin D can lead to weakened bones and increased risk of fractures.

Also see

• Vitamin D
• Cholesterol
• Ultraviolet radiation
• Calcitriol
• Rickets