ZOOLOGY STUDY GUIDE - Ye. O. Nevedomska - 2013

LECTURE 3. THE MOLECULAR LEVEL OF ORGANIZATION OF LIVING MATTER IN ANIMALS

1. Chemical elements that make up living organisms

The science that studies the chemical substances that make up living organisms, their Structure, distribution, transformation, and Functions is called biological chemistry, or biochemistry (from the Greek bios — life, and chemistry). This science began to take shape at the end of the 19th century. By the mid-20th century, The main classes of substances that make up living organisms had been discovered.

The Cells of living organisms contain almost all chemical elements known in nature. Based on their quantitative Abundance in The Cell, they can be divided into three main groups: macroelements, microelements, and ultramicroelements.

Macroelements make up the bulk of organic and inorganic substances. Four chemical elements, namely oxygen (O), hydrogen (H), carbon (C), and nitrogen (N), account for nearly 98% of the cell mass and are components of Organic compounds. Therefore, they are also called organogenic elements. What is the reason for the quantitative dominance of this "four"? Organisms are complex systems. This means that the chemical compounds they are made of must be highly diverse. For these compounds to retain their properties, they must have a stable structure. Thus, the bonds that form these substances must be strong. The chemical bond that meets these requirements is the covalent bond. Covalent bonds are formed by sharing two outer-shell electrons, one from each atom. The smaller the diameter of the atoms forming a covalent bond, the stronger the interaction between The Nucleus and the

shared electrons, and the stronger this bond is. This is why O, C, H, and N, which easily form covalent bonds, predominate in living organisms.

Macroelements also include phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), chlorine (Cl), sulfur (S), and iron (Fe). Their total share is 1.9%.

Microelements are constituent components of Enzymes and Hormones. These include more than 50 chemical elements (boron (B), cobalt (Co), copper (Cu), molybdenum (Mo), zinc (Zn), vanadium (V), iodine (I), bromine (Br), and manganese (Mn)). Their content in the cell is 10^-1 — 10^-3 %.

The content of ultramicroelements in the cell is even lower. These include gold (Au), silver (Ag), platinum (Pt), lead (Pb), and others.

All chemical elements contained in the cells of Living organisms are part of organic and Inorganic Compounds or exist in the form of ions. They play a major role in cell Nutrition, growth, the building of Tissues and Organs, maintain acid-base balance, and participate in METABOLISM and Energy Exchange, as well as in the processes of cell irritability and excitation.