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 playing vital roles, predominantly catalytic and regulatory. Although their chemical and physical properties as well as physiological Functions vary widely, vitamins share one defining characteristic: Human and Animal life and normal development are impossible without them, while the majority of these compounds cannot be synthesized by the organisms themselves.

Thus, vitamins must be obtained through diet or produced by the intestinal microflora. An imbalanced diet or the destruction of intestinal flora (for instance, due to antibiotic therapy) can lead to vitamin deficiency, severe forms of which are known as avitaminosis. Symptoms of avitaminosis include Skin and mucous membrane lesions, growth retardation, nervous and humoral system disorders, vascular fragility, bone deformation, Hair and tooth loss, and more. Since most vitamins cannot be stored in human and animal bodies, regular intake is essential to prevent deficiency. Vitamins are synthesized in plant and microbial Cells; additionally, some animals have retained The ability to synthesize specific vitamins on their own. It is believed that the requirement for vitamins in humans and most animals stems from the loss of certain Enzymes through evolutionarily driven Mutations. This is supported by the fact that the ability to synthesize certain Vitamins can be restored by adding specific precursors to the diet or under unique conditions. For example, vitamin A can be synthesized in The Human Body from carotene (a provirus/provitamin), whereas vitamin D requires exposure to ultraviolet radiation.

Vitamins were discovered by the Russian scientist N.I. Lunin in 1880, and were named later, in 1912, thanks to the research of Polish biochemist C. Funk, who isolated vitamin B₁ as a pure substance, which turned out to be an amine. Since then, similar substances—including those that are not amines—have been called vitamins, a term meaning "vital amines" (from the Latin vita meaning life). Today, over 30 vitamins are known, and they are studied by a distinct branch of biochemistry known as vitaminology.

To systematically study the Structure, properties, and Biosynthesis of vitamins, one must turn to their Classification. Vitamins are classified according to their chemical properties (solubility in Water and Lipids), chemical structure, and primary functions within the body. The nomenclature of vitamins permits The Use of trivial names (typically associated with deficiency symptoms), chemical names, and letter designations.

Based on their solubility in water or lipid Solvents, vitamins are conventionally divided into two groups: water-soluble and fat-soluble. Most Water-Soluble Vitamins belong to the B complex and serve coenzyme functions (as components of Coenzymes and prosthetic groups). The non-coenzyme properties of vitamins include participating in Metabolic Regulation, performing structural roles, serving as building blocks, exhibiting antimutagenic effects, taking part in the visual cycle, boosting the body's immune defenses, enhancing Blood Coagulation, and regulating vascular permeability, among others.

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