Phosphorus in the human body: importance, influence

Biochemistry is a branch of biology that studies the chemical composition of both individual cells and the entire organism as a whole. It is known that almost 98% of the cellular content includes atoms of oxygen, carbon, nitrogen and hydrogen. These chemical elements are called organogenic. 1.8% falls on potassium, sodium, magnesium, chlorine, phosphorus. In the human body, they are part of the mineral salts and have the appearance of simple or complex ions, ensuring the normal course of metabolic reactions. For example, the most important compounds of the cell responsible for the transmission of hereditary traits - nucleic acids - contain anionic acid residues of orthophosphoric acid.

The molecules of ATP, on which the supply of cells with energy depends , also include phosphorus-containing ions. In this article we will give examples that confirm the important role of phosphorus in the human body and its effect on metabolism.

Covalent polar bonds and their meaning

The structure of organic substances that make up living matter is based on the ability of their molecules to form a certain type of chemical bond. It is called a covalent polar and, arising between non-metal atoms, causes the basic chemical characteristics of compounds. Biochemistry, by studying the composition of the molecules of substances entering the cells of plants, fungi, animals, established their chemical composition. It turned out that, in addition to nitrogen, carbon, oxygen, they include phosphorus. In the human body, it does not occur in a free state, since it is a highly toxic substance. Therefore, in living systems, the element has the form of anions of meta-, ortho- or pyrophosphoric acid, which have the ability to form bonds with metal cations. In what substances cells can they meet?

Phosphorus in complex organic molecules

Proteins of the bone system, hormones, vitamins and lipids form complex compounds with phosphorus-containing complex ions. In the human body there are complex compounds - phospholipids and phosphoproteins, which are part of molecules of biologically active substances - enzymes and steroids. Covalent polar bonds in nucleotides of DNA and RNA provide the formation of phosphodiester bonds in nucleic acid chains. Why do we need phosphorus in the human body and what are its functions in metabolism? First, consider this issue at the cellular level of the organization.

Place of phosphorus in the elemental composition of the cell

According to the content in the cytoplasm and organelles (0.2-1%), the nonmetal is on the fourth place after the organogenic elements. The most saturated compounds of phosphorus cells of the musculoskeletal system - osteocytes, the substance of dental tissue - dentin. Their content in neurons and neuroglia, of which the nervous system is composed, is great. Phosphorus atoms are contained in membrane proteins, nucleic acids and energy-intensive substances - adenosine triphosphoric acid ATP and in the reduced form of nicotinamide dinucleotide phosphate - NADP × H ₂ . As you can see, in the human body phosphorus is contained in all vitally important structures: cells, tissues, and physiological systems.

It is known that the level of homeostasis of a cell that is an open biological system depends on the concentration of various ions in the hyaloplasm and intercellular fluid. What is the function of phosphorus in maintaining the constancy of the internal environment of the human body?

Buffer system

Due to the property of semipermeability through the outer membrane, various substances constantly enter the cell, the high concentration of which can adversely affect its vital activity. To neutralize the excess of toxic ions, the cytoplasm, together with the cations of sodium, potassium, calcium, contains acidic residues of carbonate, sulphite and phosphoric acids. They are able to react with an excess of ions trapped in the cell and monitor the constancy of intracellular contents. The buffer system, in addition to weak acid ions, necessarily includes the anions of NRO ₄ ^2- and H ₂ PO ₄ ^- containing phosphorus. In the human body, as part of the buffer system, it provides a physiologically normal course of metabolic reactions at the cellular level.

Oxidative phosphorylation

The cleavage of organic compounds in a cell is called aerobic respiration. The place of its carrying out is mitochondria. On the inner folds - the crystals of the organelles - are complexes of enzymes. For example, the ATP-as system contains electron-transporting molecules. Thanks to the reactions catalyzed by enzymes, ATP - a universal energy substance of cells, consumed for their reproduction, growth, movement - is synthesized from ADP and free molecules of phosphoric acid. Its formation can be represented in the form of a simplified reaction scheme: ADP + Φ = ATP. Then the adenosine triphosphoric acid molecules accumulate in the cytoplasm. They serve as a source of energy for performing mechanical work, for example, in the muscular system and in the reactions of plastic metabolism. Consequently, phosphorus in the human body plays a leading role in the energy exchange processes.

Phosphodiester bonds of the molecules of heredity

A high content of atomic phosphorus is recorded in the cell nucleus, since the element is part of the nucleic acids. Discovered in the 19th century by the Swiss scientist F. Micheler, they are biopolymers and consist of monomers - nucleotides. Phosphorus is present both in the purine and pyrimidine bases themselves, and in the bonds forming the RNA chains and supercoiled DNA. Monomers of nucleic acids are able to form polymeric structures due to the occurrence of covalent bonds between pentose and phosphoric acid residues by a number of lying nucleotides. They are called phosphodiester. The destruction of DNA and RNA molecules that occurs in human cells under the influence of hard gamma radiation or poisoning by toxic substances occurs due to the rupture of phosphodiester bonds. She leads the cells to death.

Biological membranes

Structures that limit the internal contents of the cell also have phosphorus in their composition. In the human body, up to 40% of the body's dry mass is in compounds containing phospholipids and phosphoproteins. They are the main components of the membrane layer, in which there are also other substances such as proteins and carbohydrates. High content of phosphorus is characteristic for the envelopes of neurocytes and their processes - dendrites and axon. Phospholipids impart plasticity to the membranes, and due to the presence of cholesterol molecules, they also have strength. They also play the role of secondary mediators-signaling molecules that are activators of effector proteins involved in conducting a nerve impulse.

Parathyroid glands and their role in phosphorus metabolism

Similar to pea, lying on both sides of the thyroid gland and having a weight of 0.5-0.8 g each, parathyroid glands secrete parathyroid hormone. It regulates the exchange of elements such as calcium and phosphorus in the human body. Their functions consist in the impact on osteocytes and osteoblasts - cells of the bone system, which under the influence of the hormone begin to secrete salts of phosphoric acid in the extracellular fluid. With hyperfunction of parathyroid glands, human bones lose strength, soften and collapse, the content of phosphorus in them falls sharply. At this time, the risk of fractures of the spine, pelvic and hip bones, which threatens the patient's life, increases. At the same time, the amount of calcium increases. This leads to hypercalcemia with symptoms of peripheral nerve damage and a decrease in the tone of skeletal muscles. Parathyroid hormone acts on the kidneys, reducing the reabsorption of phosphorus salts from the primary urine. An increase in the phosphate content in the kidney tissues causes hyperphosphaturia and the formation of stones.

Mineral composition of bone tissue

The hardness, strength and elasticity of the support system depends on the chemical composition of bone tissue cells. Osteocytes contain both organic compounds, for example the protein ossein, and inorganic substances containing phosphate salts of calcium and magnesium. With age, the amount of mineral components, such as hydroxylapatites, in man increases in osteocytes and osteoblasts. Abnormal mineralization of bone tissue, accumulation of calcium salts and excess phosphorus in the human body lead to loss of elasticity and strength of all parts of the skeleton, so older people are more often at risk of injuries and fractures.

The transformation of phosphorus compounds in the human body

The largest digestive gland in the human body - the liver - plays a leading role in the exchange reactions of phosphorus-containing substances. Hormones of the parathyroid gland and vitamin D also affect these processes. The daily requirement of the element for adults is 1.0-2.0 grams, for children and adolescents - up to 2.5 g. Phosphorus in the form of easily digestible salts, as well as in complexes with proteins and carbohydrates, enters the human body with food.

Saturated seeds of sunflower, pumpkin, hemp. In products of animal origin, phosphorus is abundant in chicken liver, beef, hard cheese varieties, fish. Excess phosphorus in the body can arise due to a violation of the reabsorption function of the kidneys, improper use of vitamins, a lack of calcium in food. The negative influence of phosphorus on the human body manifests itself primarily in the defeat of the cardiovascular system, kidneys and bone apparatus and can indicate serious metabolic disorders.