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[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).
Although the term "lipid" is sometimes used as a synonym for fats, fats are a subgroup of lipids called triglycerides. Lipids also encompass molecules such as fatty acids and their derivatives (including tri-, di-, monoglycerides, and phospholipids), as well as other sterol -containing metabolites such as cholesterol . [ 6 ]
Neutral fats, also known as true fats, are simple lipids that are produced by the dehydration synthesis of one or more fatty acids with an alcohol like glycerol. Neutral fats are also known as triacylglycerols, [ 1 ] these lipids are dense as well as hydrophobic due to their long carbon chain and are there main function is to store energy.
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.
The average amount of blood cholesterol varies with age, typically rising gradually until one is about 60 years old. There appear to be seasonal variations in cholesterol levels in humans, more, on average, in winter. [3] These seasonal variations seem to be inversely linked to vitamin C intake. [4] [5]
The consumption of saturated fat is generally considered a risk factor for dyslipidemia—abnormal blood lipid levels, including high total cholesterol, high levels of triglycerides, high levels of low-density lipoprotein (LDL, "bad" cholesterol) or low levels of high-density lipoprotein (HDL, "good" cholesterol). These parameters in turn are ...
Together with cholesterol and ceramides, free fatty acids form a water-impermeable barrier that prevents evaporative water loss. [38] Generally, the epidermal lipid matrix is composed of an equimolar mixture of ceramides (about 50% by weight), cholesterol (25%), and free fatty acids (15%). [38]
Many macromolecules are polymers of smaller molecules called monomers. The most common macromolecules in biochemistry are biopolymers ( nucleic acids , proteins , and carbohydrates ) and large non-polymeric molecules such as lipids , nanogels and macrocycles . [ 1 ]