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1.2. The chemical basis of life: inorganic and organic components

The chemical basis of life: inorganic and organic components

If we analyze each of the different types of living beings, we will find that living matter is made up of about seventy elements. These elements found in living matter are called bioelements or biogenic elements (of bios, life, and genos, origin).

These bioelements will combine to give rise to biomolecules or immediate principles.

The bioelementos can be classified by their contribution to the total mass of the body into three groups: the primary bioelements, the secondary bioelements and trace elements.

Bioelementos

  • The primary bioelements. They are essential for the formation of organic biomolecules (carbohydrates, lipids, proteins and nucleic acids), which are the molecules that make up all living beings. Biomolecules are also called immediate principles because they constitute, without intermediaries, living matter, and that is why they can be extracted from it by physical procedures (dissolution, evaporation, decantation, etc.). They are a group of six elements, which constitute 96% of all living matter. They are oxygen (O), carbon (C), hydrogen (H), nitrogen (N), and to a lesser extent, phosphorus (P) and sulfur (S).

  • The secondary bioelements are about 4% of living matter. They are found in small amounts, even less than 0.1%. In this group two types can be distinguished:
    • the indispensable ones, which cannot be absent because they are essential for the life of the cell, and which, to a greater or lesser extent, are found in all living beings. Essential secondary bioelements are calcium (Ca), sodium (Na), potassium (K), magnesium (Mg), chlorine (Cl), iron (Fe), silicon (Si), copper (Cu ), manganese (Mn), boron (B), fluorine (F) and iodine (I).
    • and variables, which may be lacking in some organisms. Variable secondary bioelements are, for example, bromine (Br), zinc (Zn), titanium (Ti), vanadium (V) and lead (Pb).

  • The trace elements are in proportions lower than 0.1% , but are essential to living things. There is no direct relationship between abundance and essentiality. Many bioelements can be, for example, trace elements, and at the same time be indispensable, since they can have a catalytic function. A large number of them is not necessary, a small number of them being sufficient for the organism to live, but the total lack would cause its death. Some trace elements, such as Fe, Cu, Zn, Mn, I, Ni and Co, appear in most organisms and others, such as Si, F, Cr, Li, B , Mo and Al, are only present in specific groups.

Fundamental ideas about the components of living matter

The bioelements or chemical elements that are part of living matter are classified into three groups:

  • Primary bioelements: the are the major components of living matter (96%). They are oxygen (O), carbon (C), hydrogen (H), nitrogen (N), and to a lesser extent,  phosphorus (P) and  sulfur (S).
  • Secondary bioelements: they are found in living matter in a lower proportion than the primary ones (4%). They are in small amounts, even less than 0.1%. There are two types of secondary bioelements:
    • the indispensable ones, which are found in all living beings. They are calcium (Ca), sodium (Na), potassium (K), magnesium (Mg), chlorine (Cl), iron (Fe), silicon (Si), copper (Cu), manganese (Mn), boron (B), fluorine (F) and iodine (I).
    • and variables, which may be lacking in some organisms. Variable secondary bioelements are,  for example, bromine (Br), zinc (Zn), titanium (Ti), vanadium (V) and lead (Pb).
  • Trace elements: although they are in proportions  lower than 0.1%, they are essential for living beings. Many of them are essential for enzymatic catalysis and for some proteins to act. Some trace elements, such as Fe, Cu, Zn, Mn, I, Ni and Co, appear in most organisms and others, such as Si, F, Cr, Li, B, Mo and Al, are only present in specific groups.