7-Dehydrocholesterol

7-Dehydrocholesterol

Chemical structure of 7-Dehydrocholesterol

7-Dehydrocholesterol is a sterol that serves as a precursor to vitamin D3 in the human body. It is a crucial component in the synthesis of vitamin D, which is essential for maintaining healthy bones and supporting the immune system.

Structure and Properties

7-Dehydrocholesterol is a cholesterol derivative with the chemical formula C27H44O. It is characterized by a double bond in the B ring of the sterol structure, which distinguishes it from cholesterol. This double bond is located between the 7th and 8th carbon atoms, hence the name 7-dehydrocholesterol.

Ball-and-stick model of 7-Dehydrocholesterol

Biosynthesis

7-Dehydrocholesterol is synthesized in the skin and other tissues from cholesterol through a series of enzymatic reactions. The enzyme 7-dehydrocholesterol reductase catalyzes the conversion of 7-dehydrocholesterol to cholesterol, which is a critical step in the biosynthesis of cholesterol.

Role in Vitamin D Synthesis

When the skin is exposed to ultraviolet B (UVB) radiation from sunlight, 7-dehydrocholesterol absorbs the UVB photons and undergoes a photochemical reaction. This reaction converts 7-dehydrocholesterol into pre-vitamin D3, which is then thermally isomerized into vitamin D3 (cholecalciferol).

Diagram of skin layers showing the location of 7-dehydrocholesterol in the epidermis

Location in the Body

7-Dehydrocholesterol is primarily found in the epidermis, the outermost layer of the skin. It is also present in other tissues, including the liver and brain, where it plays a role in cholesterol metabolism.

Clinical Significance

Deficiency in 7-dehydrocholesterol can lead to disorders such as Smith-Lemli-Opitz syndrome, a genetic condition characterized by developmental abnormalities and intellectual disability. This syndrome is caused by mutations in the gene encoding 7-dehydrocholesterol reductase, leading to an accumulation of 7-dehydrocholesterol and a deficiency in cholesterol.

Related Pages

• Vitamin D
• Cholesterol
• Ultraviolet radiation
• Smith-Lemli-Opitz syndrome

Gallery

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  Chemical structure of 7-Dehydrocholesterol
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  Ball-and-stick model of 7-Dehydrocholesterol
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  Diagram of skin layers showing the location of 7-dehydrocholesterol in the epidermis

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  7-Dehydrocholesterol chemical structure
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  7-Dehydrocholesterol molecule ball-and-stick model
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  Skin layers showing 7-Dehydrocholesterol