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 (10-4-10-6%) 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 fat cells

– 99% in

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

Polyglucides Lipids Proteins

(apoenzymes) Nucleic acids Components of

protein macromolecules

(heme, coenzymes)

Monoses Fatty acids

Alcohols (glycerol, sterols, sphingosine

Aminoacids Mononucleotides

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+ 92.2 94.0 7.5

K+ 3.0 2.7 75.0

Ca2+ 3.0 2.0 2.5

Mg2+ 1.3 1.3 15.0

Total 100% 100% 100%

Anions Cl- 69.0 76.0 7.5

HCO3- 17.0 19.3 5.0

PO32- 1.4 1.4 50.0

SO42- 0.6 0.7 10.0

organic 2.0 2.0 2.5

protein 10.0 0.6 25.0

Total 100% 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 Fe2+ or Fe3+ and Cu2+;

oxygen is bound to Fe2+ 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), SO42- (ester sulfuric

compounds)