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Protein of the Quaternary Structure: Features of Structure and Functioning

The famous philosopher once said: "Life is a form of the existence of protein bodies." And was absolutely right, because it is this organic matter that is the basis of most organisms. The quaternary protein has the most complex structure and unique properties. He will be devoted to our article. We also consider the structure of protein molecules.

What is organic matter

A large group of organic substances is united by one common property. They consist of several chemical elements. They are called organogenic. They are hydrogen, oxygen, carbon and nitrogen. They form organic substances.

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 it is monosaccharides, for lipids - glycerin and fatty acids. But DNA and RNA consist of nucleotides.

Chemical structure of proteins

Monomers of proteins are amino acids, each of which has its own chemical structure. The basis of this monomer is a carbon atom, it forms four bonds. The first of them - with a hydrogen atom. The second and third, respectively, are formed with the amino and carboxyl 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 by which all the monomers differ, which causes a huge variety of proteins and living things.

Structure of the protein molecule

One of the characteristic features of these organic substances is that they can exist at different levels of the organization. This is the primary, secondary, tertiary, quaternary structure of the protein. Each of them has certain properties and qualities.

Primary structure

This structure of the protein is the simplest in structure. It is a chain of amino acids that are linked by peptide bonds. They are formed between the amino and carboxyl 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 same elements in the functional groups of amino acids. In comparison with peptide, they have much less strength, but are able to retain this structure.

Tertiary structure

But the following structure is a tangle into which a spiral of amino acids is twisted. It is also called a globule. It exists due to the bonds that arise between the residues of only a certain amino acid - cysteine. They are called disulphide. This structure is also supported by hydrophobic and electrostatic bonds. The first are the result of attraction between amino acids in an aqueous medium. In such conditions, their hydrophobic residues practically "stick together", forming a globule. In addition, amino acid radicals have opposite charges, which are attracted to each other. As a result, additional electrostatic bonds arise.

Quaternary protein

Quaternary structure of the protein is the most complex. This is the result of the fusion of several globules. They can differ in chemical composition, and in the features of 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 case when non-protein components are attached to these molecules, proteids appear. Most often this compound of amino acids with carbohydrates, nucleic and phosphoric acid residues, lipids, individual atoms of iron and copper. Complexes of proteins with natural coloring substances - pigments - are also known in nature. Such a structure of protein molecules is more complex.

The spatial form of the quaternary structure of the protein is crucial for its properties. Scientists found that filamentous or fibrillar biopolymers do not dissolve in water. They perform the most important functions for living organisms. So, the muscle proteins actin and myosin provide movement, and keratin is the basis of the human and animal hair. Spherical or globular proteins of the quaternary structure are readily soluble in water. Their role in nature is different. Such substances are capable of transporting gases like hemoglobin of blood, splitting food like pepsin, or performing a protective function, like antibodies.

Protein properties

The quaternary structure, especially the globular protein, can change its structure. There is this process under the influence of various factors. Most often they are high temperature, concentrated acids or heavy metals.

If the protein molecule is untwisted to a chain of amino acids, this property is called denaturation. This process is reversible. This structure is able to again form globules of molecules. Such an inverse process is called renaturation. If the amino acid molecules separate from one another and break peptide bonds, destruction occurs. This process is irreversible. Such a protein can not be restored. Destruction was carried out by each of us, when fried eggs.

Thus, the quaternary structure of the protein is the type of bond that is formed in a given molecule. It is strong enough, but under the influence of certain factors it is capable of breaking down.

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