Biochemistry and Molecular Biology - Belyasova N.A. 2002

Metabolism. Energy-requiring processes
Biological role and biosynthesis of vitamins
General characteristics of vitamins

Vitamins comprise a group of low-molecular-weight Organic compounds required by the body in trace amounts, yet performing vital Functions, most commonly catalytic and regulatory. Although their chemical and physical properties as well as physiological roles vary widely, vitamins share one essential characteristic: normal growth and functioning of humans and animals are impossible without them, while the majority of these compounds cannot be synthesized independently by the organisms themselves.

Thus, vitamins must be supplied with food or produced by intestinal microflora. An imbalanced diet or the destruction of intestinal microflora (for instance, As a result of antibiotic therapy) can lead to vitamin deficiency, the severe form of which is known as avitaminosis. Symptoms of avitaminosis include Skin and mucous membrane lesions, growth retardation, Disorders of the nervous and humoral systems, vascular fragility, bone curvature, Hair and tooth loss, and others. Because most vitamins cannot accumulate in the bodies of humans and animals, it is crucial to regularly replenish their supply. Vitamins are synthesized in the Cells of plants and microorganisms; additionally, some animals have retained The ability to synthesize certain vitamins on their own. The Human and Animal requirement for vitamins is believed to stem from the loss of specific Enzymes due to Mutations. This is supported by the restoration of the ability to synthesize certain vitamins when specific precursors are added to the diet or under special conditions. For example, vitamin A can be synthesized in The Human Body from carotene (a provitamin), whereas vitamin D requires exposure to ultraviolet radiation.

Vitamins were discovered by the Russian scientist N.I. Lunin in 1880, and they received their name later, in 1912, thanks to the research of Polish biochemist C. Funk, who isolated pure vitamin B₁, which turned out to be an amine. Since then, such compounds, including those that are not amines, have been called vitamins, which translates to "vital amines" (from the Latin vita meaning life). Currently, more than 30 vitamins are known, and they are studied by a distinct branch of biochemistry known as vitaminology.

For a systematic Study of the Structure, properties, and Biosynthesis of vitamins, one should turn to their Classification. Vitamins are classified according to their chemical properties (solubility in Water and Lipids), chemical structure, and main functions in the body. The nomenclature of vitamins permits The Use of trivial names (typically associated with the symptoms of avitaminosis), chemical names, and letter designations.

Based on their solubility in water or lipid Solvents, vitamins are generally divided into two groups: water-soluble and fat-soluble. Most Water-Soluble Vitamins belong to the B-complex group and perform coenzyme functions (being components of Coenzymes and prosthetic groups). Non-coenzyme properties of vitamins include the ability to participate in Metabolic Regulation, perform structural functions, serve as building blocks, exhibit antimutagenic activity, participate in the visual cycle, enhance the body's defense mechanisms, increase Blood clotting, and regulate vascular permeability, among others.

In addition to vitamins, there is another category of substances with vitamin-like properties known as Vitamin-like compounds, although there is no sharp boundary between these groups.