MAJOR CHEMICAL COMPONENTS OF THE LIVING ORGANISMS Medical Biochemistry Molecular Principles of Structural Organization of Cells

CHEMICAL COMPOSITION OF LIVING ORGANISMS In the human organism there are 70 elements of the Periodic Table, which may be divided in four groups: –Macrobiogenic elements (>1%) O, C, N, H, Ca, P. –Oligobiogenic elements (0,1-1%) Na, K, Cl, S, Mg, Fe. –Microbiogenic elements (<0.01%) Zn, Mn, Co, Cu, F, B, I. –Ultramicrobiogenic elements ( %) Li, Al, Si, Cd, Cr, Ni. They are constituents of organic and inorganic compounds. Exception: The oxygen molecular form, besides being bound to hemoglobin or myoglobin, is dissolved in biological fluids. There are other gases (nitrogen, inert gases) which are partly dissolved in the biological liquids but do not take part in the biochemical processes

CHEMICAL COMPOSITION OF LIVING ORGANISMS Organic compounds. Different cells can vary in the content of proteins, nucleic acids, lipids, polysaccharides, for example: –Liver and muscle cells are rich in polysaccharides –Fat tissue cells are rich in lipids –Animal cells are rich in proteins and rather depleted in nucleic acids as compared with plant cells The water content is different –40% in plant cells, fat cells –99% in medusa Inorganic compounds are in small number but have vital functions in the organism

Cell Cellular organelles (nuclei, mitochondria,etc) Enzymes complexes, ribosomes, nucleoli, contractile system Conjugated proteins: Glycoproteins, Lipoproteins, Phosphoproteins, Nucleoproteins, Metalproteins, Chromoproteins PolyglucidesLipids Proteins (apoenzymes) Nucleic acids Components of protein macromolecules (heme, coenzymes ) Monoses Fatty acids Alcohols (glycerol, sterols, sphingosine AminoacidsMononucleotides Intermediary metabolites Inorganic compounds LEVELS OF MOLECULAR ORGANIZATION OF CELL

WATER Is indispensable for life due to its unique physical and chemical properties and importance for biological activity of living organisms Content 45-75% of the total body mass –depends on age (new born 75%, >50years 45-50%) –the content varies depending on the metabolic processes in the specified tissue (10% in the fat tissue, 65-70% in other tissues, 80% in the blood and kidney) –maintained at the necessary level through intake (2 liters/day) or produced in the metabolic processes (0.3 liters/day) Distribution: –In the cells (intracellular) –Outside the cells extracellular fluids (12-16%), blood plasma (5%), lymph (2%) –Within closed cavities (intra-cavity water)(1-3%): cerebrospinal fluid, intraocular, pericardial, synovial fluid etc

WATER Functions : –Dissolution and stabilization of biological molecules and ions in the fluids of the organisms –Heat balance control - uptake, conservation, distribution and release of heat –Transport – supply of nutrients and excretion of waste products –Mechanical (by hydration) – assistance in maintaining intracellular pressure and shape of cells –Structural – forming an interlayer between the polar ends of protein and lipids in biological membranes –Synthetic (anabolic) – substrate in the synthesis of biological compounds –Hydrolytic (catabolic) – substrate in the bond-breaking processes –Energetic (electron donating) The cell functions are dependent on: –The total amount of intra and extracellular water –Hydration of sub-cellular structures –Aqueous microenvironment of macromolecules

INORGANIC IONS Ions Plasma (%) Extracellular (%) Intracellular (%) Cations Na K+K+K+K Ca Mg Total100%100%100% Anions Cl HCO PO SO organic protein Total100%100%100%

INORGANIC IONS Functions –Bioelectric functions – development of potential difference across the cell membrane (neurons, muscle cells) –Osmotic functions – control of osmotic and hydro-osmotic pressure –Structural – metal ions constituents of macromolecules (proteins, heme) –Regulatory – cations exert regulatory action directly binding to enzymes, influencing their activity and rate of the chemical reactions in the cell, or Indirectly, influencing the hormonal regulation –Transport – electrons are transported by the cytochromes, enzymes containing Fe 2+ or Fe 3+ and Cu 2+ ; oxygen is bound to Fe 2+ in the structure of hemoglobin –Energetic – inorganic phosphate in ATP –Mechanical (support) – Ca and P ions are constituents of bones (strength) –Synthetic – complex molecules contain I - (hormones), SO 4 2- (ester sulfuric compounds)