Classification of elements by quantitative content
Professor D. R. Williams proposed calling biogenic elements the "elements of life." Depending on their percentage share in the body, three main groups are distinguished:
- Organogens (macronutrients): collectively account for about 98% of the cell mass. Oxygen leads (65–75%), followed by carbon (15–18%), hydrogen (8–10%), and nitrogen (1.5–3.0%).
- Second-group macronutrients (about 1.9%): sulfur, phosphorus, chlorine, potassium, sodium, magnesium, calcium, iron.
- Micronutrients (about 0.1% or less): zinc, copper, iodine, fluorine, manganese, selenium, cobalt, molybdenum, strontium, nickel, chromium, vanadium, and others.
The cell consists of organic compounds and inorganic substances. Among inorganic components, water dominates (70–80%), serving as the medium for metabolic transformations.
Biological role of key macronutrients
Each element performs strictly defined structural or regulatory tasks at the cellular and tissue levels:
- Oxygen (O) acts as a key oxidizing agent in energy production during enzymatic reactions and is part of the structure of water and all major biomolecules.
- Carbon, hydrogen, and nitrogen form the molecular skeleton of proteins, lipids, carbohydrates, and nucleic acids. Nitrogen is concentrated in amino groups, purine and pyrimidine bases, and coenzymes.
- Sodium and potassium ensure the generation and conduction of nerve impulses, muscle contraction, and maintain osmotic pressure and acid-base balance. Potassium ions, together with magnesium, regulate ribosome function.
- Calcium accumulates in bone tissue (up to 1 kg), regulates blood clotting, and the mechanics of muscle fiber contraction.
- Phosphorus is part of membrane phospholipids, high-energy compounds (ATP), coenzymes (NADP), and nucleic acids. In mineral form, it is represented by hydroxyapatite Ca₅(PO₄)₃OH in bones and teeth.
- Iron is essential for oxygen transport by hemoglobin and myoglobin, and is also part of cytochromes, metalloflavoproteins, and iron-sulfur proteins.
Functions of micronutrients and enzymatic catalysis
Micronutrients are present in extremely low concentrations, but cellular metabolism is impossible without them. Their basic systemic significance is acting as cofactors and activators of protein enzymes:
| Element | Main biochemical role |
|---|---|
| Iodine (I) | Structural component of thyroid hormones |
| Copper (Cu) | Participation in respiratory enzymes, hematopoiesis, and hemoglobin maturation |
| Zinc (Zn) | Component of enzymatic systems controlling normal growth processes |
| Cobalt (Co) | Part of the molecular structure of vitamin B₁₂ |
| Manganese (Mn) | Activation of cellular respiration and fatty acid oxidation enzymes |
| Fluorine (F) | Formation and maintenance of dental tissue structure |
Mineral bioavailability and absorption factors
The assimilation of dietary mineral components depends on their chemical form and diet composition. General rule: soluble ionized forms and chelated complexes are absorbed more efficiently than inorganic salts.
- Iron: absorbed by enterocytes as Fe²⁺. Vitamin C is oxidized to dehydroascorbic acid and reduces ferric iron (Fe³⁺) to ferrous iron, facilitating absorption. Heme iron from meat is absorbed independently of dietary factors (by 15–35%), whereas non-heme iron is blocked by tea tannins and dietary fiber.
- Calcium: requires strict balance. The optimal ratio with phosphorus (Ca:P) is 1:1.5, and with magnesium (Ca:Mg) is 1:0.7. Excess phosphates or oxalic acid (spinach, sorrel) precipitate calcium into insoluble salts. Caffeine accelerates mineral loss, while lactose enhances intestinal absorption.
- Iodine: with dietary iodine deficiency, it is important to limit sulfur-containing goitrogens (cabbage, radishes, peanuts) that hinder its full utilization.
The four main organogens are easily remembered by the Latin symbols: O-C-H-N.
Class and exam questions
In what form is iron absorbed, and what role does ascorbic acid play?
Ionized ferrous iron (Fe²⁺) is absorbed in the intestine. Ascorbic acid acts as a reducing agent: it converts Fe³⁺ into the Fe²⁺ form, turning itself into dehydroascorbic acid.
What is the optimal ratio of calcium, phosphorus, and magnesium in the diet?
For the adult body, the optimal Ca:P proportion is 1:1.5, and Ca:Mg is 1:0.7. Balance disruption leads to insoluble salt formation and calcium loss.
What dietary components reduce mineral bioavailability?
Absorption is reduced by phytic acid in grains, oxalic acid (forming insoluble salts with calcium), plant dietary fibers, tea tannins, and excess caffeine.
What else to study on this topic
- Iron transport and storage proteins: physiological role of ferritin and transferrin
- Bacterial iron scavenging mechanisms using siderophores
- Phosphorylation as a leading biochemical mechanism of energy transfer
- Goitrogens of cruciferous vegetables and their effect on iodine metabolism
- The role of lactose as a prebiotic stimulating microbiota and mineral absorption
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