Biochemical Foundations of Human Vital Activity - Volkov N.I., Nesen E.N. 2000

Biochemical Foundations of Human Vital Activity
Vitamins
Vitamin-like compounds

In recent years, a group of chemical substances has been identified which, much like Vitamins, play a crucial regulatory role, yet do not possess all the properties characteristic of vitamins. They are referred to as Vitamin-like compounds. Many of these substances are synthesized within the body, meaning that avitaminosis (vitamin deficiency states) does not typically occur. The daily requirement for Vitamin-like substances is significantly higher than that for actual vitamins (Table 11).

Class="center">TABLE 11 Daily adult requirement for vitamin-like substances and their dietary sources

Choline

Biological action. Choline (vitamin B₄) serves as a donor of methyl groups utilized in the Synthesis of the essential amino acid Methionine and participates in Protein METABOLISM. It is a component of acetylcholine, a chemical neurotransmitter of The Nervous system, and thus plays a role in the transmission of nerve impulses. As a constituent of Phospholipids, it performs a lipotropic function—protecting the liver from fatty degeneration and promoting Glycogen storage within it.

Hypovitaminosis. Choline deficiency can develop when Dietary Protein Intake is inadequate, manifesting as metabolic disturbances in the liver, kidneys, and heart Muscle, which lead to fat accumulation in these Tissues and Organs.

Chemical Structure. Choline is a nitrogenous derivative of ethyl alcohol containing three methyl groups attached to the nitrogen atom, which confer vitamin activity upon the substance:

Choline is readily soluble in Water and alcohol. Large doses exert a toxic effect on The Human Body. Choline was first isolated from Bile in 1892.

Pangamic acid

Biological action. Pangamic acid (vitamin B₁₅) enhances oxygen uptake by body tissues and increases resistance to Hypoxia, thereby improving oxidative processes and preventing fatigue during muscular activity. Due to the presence of methyl groups in its molecule, vitamin B₁₅ is used for the synthesis of Creatine phosphate in Muscles, influences liver glycogen content, and enhances The oxidation of fats in the liver.

Since pangamic acid is found in numerous food products, humans do not typically experience a deficiency in it.

Chemical structure. Pangamic acid is an ester of D-gluconic acid and dimethylglycine:

Currently, vitamin B₁₅ is used in sports practice to prevent hypoxia, particularly during training in mid-altitude and high-altitude conditions.

Orotic acid

Biological action. Orotic acid (vitamin B₁₃) is utilized in the synthesis of NUCLEOTIDES and Nucleic Acids, which is associated with enhanced Protein Synthesis AND growth processes. It is also used to increase muscle mass (anabolic effect), improve hematopoiesis (Blood formation), and accelerate bodily recovery. Orotic acid, particularly in combination with vitamin B₁₂ and folic acid, corrects impaired cardiac contractile function.

Chemical structure. Orotic acid is a pyrimidine derivative and can exist in two interconvertible forms:

Ubiquinone (Coenzyme Q)

Biological action. Ubiquinone is a critical coenzyme in the Biological Oxidation of nutrients and energy production within Cells. As a component of the mitochondrial Respiratory Chain, it facilitates hydrogen transfer across membranes to Cytochromes. Coenzyme Q is included in many nutritional formulas used for weight management and athletic performance enhancement, as well as in topical rubs designed to improve energy production in joints and muscles.

Chemical structure. Ubiquinone features a benzene ring linked to various groups (2,3-dimethoxy-methyl-1,4-benzoquinone with an isoprenoid chain at the sixth position):

Ubiquinone is a widely distributed coenzyme, hence its name—the "ubiquitous quinone". It has been detected in all living cells. Within cells, ubiquinone is localized apparently exclusively within the Cell/35.html">Mitochondria.

Carnitine

Biological role. Carnitine (vitamin B_t) is involved in protein and Lipid Metabolism. Present in most body cells, including muscle fibers, it enhances aerobic energy production by transporting Fatty acids into the mitochondria, where they undergo oxidation to release energy. By stimulating Fatty acid oxidation, carnitine helps preserve glycogen reserves in cells, while its role in lipid metabolism prevents The Development of atherosclerosis.

Chemical structure. It is synthesized from The amino acid Lysine and has the following chemical formula:

Carnitine is used to treat muscular dystrophy and serves as an effective ergogenic aid to boost endurance performance in athletes.    

Vitamin U    

Biological role. Vitamin U (from Latin ulcus — ulcer) prevents the development of gastric ulcers. It acts as a methyl group donor essential for the synthesis of choline, creatine, and adrenaline. By methylating histamine, it converts it into an inactive form, thereby helping to reduce gastric secretory function and promote ulcer healing.

Chemical structure. Vitamin U is S-methylmethionine:

It is readily soluble in water, stable in acidic environments, and easily destroyed at 100 °C. It was first isolated in 1950 from the juice of fresh cabbage and other raw vegetables.

Lipoic Acid

Biological role. Lipoic acid (vitamin F) is an essential component of enzyme systems responsible for the oxidation of pyruvic acid to acetyl-CoA and a-ketoglutaric acid in The Tricarboxylic Acid Cycle. Consequently, it regulates aerobic energy production processes in The Cell associated with the oxidation of CARBOHYDRATES and fats. This vitamin influences Cholesterol Metabolism and exhibits lipotropic activity.

Lipoic acid can exist in both oxidized and reduced forms:

Para-Aminobenzoic Acid (PABA)

Biological role. PABA is a component of folic acid; it enhances the synthesis of Nucleic Acids and Proteins, and activates growth processes. Symptoms of PABA deficiency in humans have not been established, as it is found in A wide variety of foods.

Inositol

Biological role. Inositol (vitamin B₈) exerts a lipotropic effect on the liver, preventing fatty degeneration, and participates in regulating the motility of The Stomach and intestines while maintaining the normal functional state of the nervous system.

A lack of dietary inositol leads to Metabolic Disorders, growth arrest, Hair loss, and slowed recovery processes after physical exertion.

Chemical structure. Inositol is a hexahydric alcohol of cyclohexane:

In plant-derived products, inositol occurs as phytin (a mixture of calcium and magnesium salts of inositol phosphoric acid).

Review Questions

1. What are vitamins?

2. What is the body's requirement for vitamins, and what factors does it depend on?

3. What is the MECHANISM OF ACTION of vitamins? Name the most important Coenzymes that incorporate vitamins.

4. On what basis are vitamins classified? Name the main representatives of each class.

5. What states of the Organism are observed depending on the vitamin supply?

6. What is The Role of individual fat-soluble and Water-Soluble Vitamins in the REGULATION OF METABOLISM?

7. What vitamin-like substances do you know? Which of them enhance energy production in skeletal muscles?

8. Which vitamins have an anabolic effect? What does this mean?

9. Which vitamins possess antioxidant properties? Is there a need for them under various physical loads? Why?

10. Which vitamins are involved in the Energy supply of skeletal muscles?

11. Why do the recommended dietary allowances of vitamins increase for athletes?