Biochemistry is a branch of biology that studies the chemical composition of both individual cells and the whole organism. Almost 98% of cellular contents are known to include oxygen, carbon, nitrogen, and hydrogen atoms. These chemical elements are called organogenic. 1.8% are potassium, sodium, magnesium, chlorine, phosphorus. In the human body, they are part of mineral salts and have the form of simple or complex ions, ensuring the normal course of metabolic reactions. For example, the most important cell compounds responsible for the transmission of hereditary traits â nucleic acids â contain anions of acid residues of phosphoric acid.
ATP molecules, on which the energy supply of cells depends , also include phosphorus-containing ions. In this article we will give examples confirming 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 covalent polar and, arising between non-metal atoms, determines the main chemical characteristics of the compounds. Biochemistry, studying the composition of the molecules of substances that make up the cells of plants, fungi, animals, established their chemical composition. It turned out that, in addition to nitrogen, carbon, oxygen, they also 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. What cell substances can they be found in?
Phosphorus as part of complex organic molecules
Proteins of the skeletal system, hormones, vitamins and lipids form complex compounds with phosphorus-containing complex ions. The human body contains complex compounds - phospholipids and phosphoproteins, which are part of the molecules of biologically active substances - enzymes and steroids. Covalent polar bonds in DNA and RNA nucleotides provide the formation of phosphodiester bonds in the nucleic acid chains. Why is phosphorus needed in the human body and what are its functions in metabolism? First, consider this issue at the cellular level of organization.
The place of phosphorus in the elemental composition of the cell
According to the content in the cytoplasm and organelles (0.2-1%), non-metal is in fourth place after organogenic elements. The cells of the musculoskeletal system are most saturated with phosphorus compounds - osteocytes, the substance of the dental tissue is dentin. Their content is high in the neurons and neuroglia that make up the nervous system. Phosphorus atoms are contained in membrane proteins, nucleic acids and energy-intensive substances - ATP adenosine triphosphoric acid and in the reduced form of nicotinamidine nucleotide phosphate - NADP Ã H 2 . As you can see, in the human body, phosphorus is contained in all vital structures: cells, tissues, physiological systems.
It is known that the level of homeostasis of a cell, which 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 semi-permeability property, various substances constantly enter the cell through the outer membrane, a high concentration of which can negatively affect its vital activity. To neutralize the excess of toxic ions, the cytoplasm, together with cations of sodium, potassium, calcium, contains acid residues of carbonate, sulfite and phosphoric acids. They are able to react with an excess of ions entering the cell and control the constancy of intracellular contents. The buffer system, in addition to ions of weak acids, necessarily includes anions of NRO 4 2- and 2 4 - containing phosphorus. In the human body, as part of the buffer system, it ensures the physiologically normal course of metabolic reactions at the cellular level.
Oxidative Phosphorylation
The breakdown of organic compounds in the cell is called aerobic respiration. The venue is mitochondria. Complexes of enzymes are located on the inner folds - organelle cristae. For example, the ATPase system contains electron carrier molecules. Thanks to reactions catalyzed by enzymes, ATP is synthesized from ADP and free phosphoric acid molecules - the universal energy substance of cells spent on their reproduction, growth, movement. Its formation can be represented in the form of a simplified reaction scheme: ADP + F = ATP. Then the molecules of adenosine triphosphoric acid accumulate in the cytoplasm. They serve as a source of energy for performing mechanical work, for example, in the muscular system and in plastic exchange reactions. Consequently, phosphorus in the human body plays a leading role in the processes of energy exchange.
Phosphodiester bonds of heredity molecules
A high content of atomic phosphorus is recorded in the cell nucleus, since the element is part of nucleic acids. Discovered in the 19th century by the Swiss scientist F. Mischer, 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 DNA supercoil . Nucleic acid monomers are capable of forming polymer structures due to the occurrence of covalent bonds between pentose and phosphoric acid residues of adjacent 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 due to poisoning by toxic substances occurs due to rupture of phosphodiester bonds. It causes cells to die.
Biological membranes
Structures that limit the internal contents of the cell also contain phosphorus. In humans, up to 40% of dry body weight falls on compounds containing phospholipids and phosphoproteins. They are the main components of the membrane layer, which also contains substances such as proteins and carbohydrates. A high phosphorus content is characteristic of the membranes of neurocytes and their processes - dendrites and axon. Phospholipids give membranes plasticity, 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 the conduct of a nerve impulse.
Parathyroid glands and their role in phosphorus metabolism
Similar to peas, lying on both lobes of the thyroid gland and weighing 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 are to influence osteocytes and osteoblasts - cells of the skeletal system, which, under the influence of the hormone, begin to secrete salts of phosphoric acid into the extracellular fluid. With hyperfunction of the parathyroid glands, human bones lose strength, soften and collapse, their phosphorus content drops sharply. At this time, the risk of fractures of the spine, pelvic bones, and hips that threaten the life of the patient increases. At the same time, the amount of calcium increases. This leads to hypercalcemia with symptoms of peripheral nerve damage and a decrease in skeletal muscle tone. Parathyroid hormone also acts on the kidneys, reducing the reabsorption of phosphorus salts from primary urine. An increase in the phosphate content of the kidney tissue causes hyperphosphaturia and stone formation.
Bone mineral composition
The hardness, strength and elasticity of the support system depends on the chemical composition of bone cells. Osteocytes contain both organic compounds, for example, ossein protein, and inorganic substances containing phosphate salts of calcium and magnesium. With age, the amount of mineral components, such as hydroxylapatites, in osteocytes and osteoblasts increases in humans. Abnormal mineralization of bone tissue, the accumulation of calcium salts and excess phosphorus in the human body lead to a loss of elasticity and strength of all parts of the skeleton, so older people are more likely to be at risk of injuries and fractures.
The conversion of phosphorus compounds in the human body
The largest digestive gland in the human body - the liver - plays a leading role in the metabolism of phosphorus-containing substances. Hormones of the parathyroid gland and vitamin D also affect these processes. The daily requirement of an element for adults is 1.0â2.0 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.
They are saturated with sunflower seeds, pumpkins, hemp. There is a lot of phosphorus in animal products in chicken liver, beef, hard cheese, and fish. An excess of phosphorus in the body can occur due to a violation of the reabsorption function of the kidneys, improper use of vitamins, and a lack of calcium in food. The negative effect of phosphorus on the human body is manifested primarily in damage to the cardiovascular system, kidneys and bone apparatus and may indicate serious metabolic disorders.