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The epidermal strata of the skin. 7-Dehydrocholesterol (7-DHC) is a zoosterol that functions in the serum as a cholesterol precursor, and is photochemically converted to vitamin D 3 in the skin, therefore functioning as provitamin-D 3. The presence of this compound in human skin enables humans to manufacture vitamin D 3 (cholecalciferol).
Membrane lipids are a group of compounds (structurally similar to fats and oils) which form the lipid bilayer of the cell membrane. The three major classes of membrane lipids are phospholipids, glycolipids, and cholesterol. Lipids are amphiphilic: they have one end that is soluble in water ('polar') and an ending that is soluble in fat ...
Cholesterol is extracted from wool grease and wool wax alcohols obtained from the cleaning of wool after shearing. The cholesterol undergoes a four-step process to make 7-dehydrocholesterol, the same compound that is produced in the skin of animals. The 7-dehydrocholesterol is then irradiated with ultraviolet light.
[2] [3] The most familiar type of animal sterol is cholesterol, which is vital to the structure of the cell membrane, and functions as a precursor to fat-soluble vitamins and steroid hormones. While technically alcohols, sterols are classified by biochemists as lipids (fats in the broader sense of the term).
Cholesterol is the principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils. [3] [4]Cholesterol is biosynthesized by all animal cells [citation needed] and is an essential structural and signaling component of animal cell membranes.
Sterols, such as cholesterol and its derivatives, are an important component of membrane lipids, [43] along with the glycerophospholipids and sphingomyelins. Other examples of sterols are the bile acids and their conjugates, [ 44 ] which in mammals are oxidized derivatives of cholesterol and are synthesized in the liver.
Levin also cautions people this summer to seek shade during peak sun (10 a.m. to 4 p.m.) and avoid tanning beds as they're also associated with significant skin cancer risk.
In animals, these fats are obtained from food and are synthesized by the liver. [1] Lipogenesis is the process of synthesizing these fats. [2] [3] The majority of lipids found in the human body from ingesting food are triglycerides and cholesterol. [4] Other types of lipids found in the body are fatty acids and membrane lipids.