The famous philosopher once said: "Life is a form of existence of protein bodies." And he was absolutely right, because it is this organic substance that is the basis of most organisms. The quaternary structure protein has the most complex structure and unique properties. Our article will be devoted to him. Also consider the structure of protein molecules.
What is organic matter
A large group of organic substances shares one common property. They consist of several chemical elements. They are called organogenic. These are hydrogen, oxygen, carbon and nitrogen. They form organic matter.
Another common feature is that they are all biopolymers. These are large macromolecules. They consist of a large number of repeating parts called monomers. For carbohydrates, these are monosaccharides, for lipids, glycerin and fatty acids. But DNA and RNA are made up of nucleotides.
The chemical structure of proteins
Protein monomers are amino acids, each of which has its own chemical structure. At the heart of this monomer is a carbon atom, it forms four bonds. The first one is with a hydrogen atom. And the second and third, respectively, are formed with an amino and carboxy group. They determine not only the structure of biopolymer molecules, but also their properties. The last group in an amino acid molecule is called a radical. This is precisely the group of atoms in which all monomers differ from each other, which leads to a huge variety of proteins and living things.
The structure of the protein molecule
One of the characteristic features of these organic substances is that they can exist at different levels of organization. This is the primary, secondary, tertiary, quaternary structure of the protein. Each of them has certain properties and qualities.
Primary structure
This protein structure is the simplest in structure. It is a chain of amino acids that are connected by peptide bonds. They are formed between the amino and carboxo groups of neighboring molecules.
Secondary structure
When a chain of amino acids is twisted into a spiral, a secondary protein structure is formed. The bond in such a molecule is called hydrogen, and its atoms form the elements of the same name in the functional groups of amino acids. Compared to peptide ones, they have a much lower strength, but are able to retain this structure.
Tertiary structure
But the next structure is a ball in which a spiral of amino acids is twisted. It is also called a globule. It exists thanks to the bonds arising between the residues of only a certain amino acid - cysteine. They are called disulfide. Hydrophobic and electrostatic bonds also support this structure. The former are the result of attraction between amino acids in an aqueous medium. Under such conditions, their hydrophobic residues practically “stick together”, forming a globule. In addition, amino acid radicals have opposite charges that attract each other. As a result, additional electrostatic bonds arise.
Quaternary structure protein
The quaternary structure of the protein is the most complex. This is the result of merging several globules. They can vary both in chemical composition and in spatial organization. If the protein of the Quaternary structure is formed only from amino acid residues, it is simple. Such biopolymers are also called proteins. But in the event that non-protein components are attached to these molecules, proteids arise. Most often this is a combination of amino acids with carbohydrates, nucleic and phosphoric acid residues, lipids, individual iron and copper atoms. In nature, complexes of proteins with natural coloring substances - pigments - are also known. This structure of protein molecules is more complex.
The spatial form of the quaternary structure of the protein is crucial for its properties. Scientists have found that filiform or fibrillar biopolymers do not dissolve in water. They perform essential functions for living organisms. So, muscle proteins actin and myosin provide movement, and keratin is the basis of the hair of humans and animals. Spherical or globular quaternary structure proteins are highly soluble in water. Their role in nature is different. Such substances can transport gases like blood hemoglobin, break down food like pepsin, or carry out a protective function, like antibodies.
Protein properties
A protein of the Quaternary structure, especially globular, can change its structure. This process occurs under the influence of various factors. Most often, they are high temperature, concentrated acids or heavy metals.
If a protein molecule unwinds to a chain of amino acids, this property is called denaturation. This is a reversible process. This structure is able to form globules of molecules again. This reverse process is called renaturation. If amino acid molecules depart from each other and peptide bonds break, destruction occurs. This process is irreversible. Such a protein cannot be restored. Destruction was carried out by each of us when fried fried eggs.
Thus, the quaternary structure of a protein is the type of bond that forms in a given molecule. It is strong enough, but under the influence of certain factors, it can collapse.