A huge number of different compoundsa different chemical nature man managed to synthesize in laboratory conditions. However, all the same, the most important and significant for the life of all living systems were, is and will remain natural, natural substances. That is, those molecules that participate in thousands of biochemical reactions within organisms and are responsible for their normal functioning.
The vast majority of them belong to a group called "biological polymers."
General concept of biopolymers
First of all, it should be said that all thesecompounds - high molecular weight, having a mass of up to millions of Daltons. These substances are animal and vegetable polymers, which play a decisive role in the construction of cells and their structures, providing metabolism, photosynthesis, respiration, nutrition and all other vital functions of any living organism.
Переоценить значение таких соединений сложно.Biopolymers are natural substances of natural origin, formed in living organisms and are the basis of all life on our planet. What exactly are the connections to them?
Biopolymers of a cell
There are a lot of them. So, the main biopolymers are the following:
- proteins;
- polysaccharides;
- nucleic acids (DNA and RNA).
In addition to them, many mixed polymers formed from the combinations of the already listed are also included here. For example, lipoproteins, lipopolysaccharides, glycoproteins and others.
Common Properties
We can distinguish several features that are inherent in all the molecules under consideration. For example, the following general properties of biopolymers:
- a large molecular mass due to the formation of huge macrochains with branching in the chemical structure;
- types of bonds in macromolecules (hydrogen, ionic interactions, electrostatic attraction, disulfide bridges, peptide bonds, etc.);
- the structural unit of each chain is a monomer unit;
- Stereoregularity or its absence in the structure of the chain.
But in general, all biopolymers still have more differences in structure and functions than similarities.
Proteins
Huge significance in the life of any living beingshave protein molecules. Such biopolymers are the basis of the whole biomass. After all, even according to the theory of Oparin-Haldane, life on Earth originated from a coacervate droplet, which was a protein.
The structure of these substances complies with strictorderliness in the structure. The basis of each protein is amino acid residues, which are able to connect with each other in an unlimited chain length. This occurs by the formation of special bonds - peptide bonds. Such a bond is formed between four elements: carbon, oxygen, nitrogen and hydrogen.
The composition of the protein molecule can include a lotamino acid residues, both the same and different (several tens of thousands or more). In total, there are 20 types of amino acids found in these compounds. However, their diverse combination allows proteins to flourish in quantitative and species terms.
Protein biopolymers have different spatial conformations. Thus, each representative can exist in the form of a primary, secondary, tertiary, or quaternary structure.
The most simple and linear of them is primary. It is simply a series of amino acid sequences joined together.
Secondary conformation is more complex.structure, as the common macrochain of the protein begins to spiral, forming coils. Two adjacent macrostructures are held next to each other due to covalent and hydrogen interactions between the groups of their atoms. There are alpha and beta-helix of the secondary structure of proteins.
The tertiary structure is a collapsedin a ball one macromolecule (polypeptide chain) protein. A very complex network of interactions within a given globule allows it to be sufficiently stable and to keep its adopted form.
Quaternary conformation is somewhatpolypeptide chains, coiled and spirally twisted into a ball, which at the same time also form multiple bonds of various types among themselves. The most complex globular structure.
Functions of protein molecules
- Transport.It is carried out by the cell-proteins that are part of the plasma membrane. It is they who form the ion channels through which certain molecules are able to pass. Also, many proteins are part of the simplest movement of organisms and bacteria, therefore, are directly involved in their movement.
- Energy function is performed by datamolecules are very active. One gram of protein in the process of metabolism forms 17.6 kJ of energy. Therefore, the consumption of plant and animal products containing these compounds is vital for living organisms.
- The building function is to participateprotein molecules in the construction of most cellular structures, the cells themselves, tissues, organs, and so on. Virtually any cell is basically built from these molecules (cytoplasm cytoskeleton, plasma membrane, ribosome, mitochondria, and other structures are involved in the formation of protein compounds).
- The catalytic function is carried out by enzymeswhich by their chemical nature are nothing more than proteins. Without enzymes, most biochemical reactions in the body would be impossible, since they are biological catalysts in living systems.
- Receptor (also signaling) function helps cells to orient themselves and respond correctly to any environmental changes, both mechanical and chemical.
If we consider the proteins in more depth, we can distinguish some other minor functions. However, the listed are basic.
Nucleic acids
Such biopolymers are an important part of eachcells, be it prokaryotic or eukaryotic. Indeed, nucleic acids include DNA molecules (deoxyribonucleic acid) and RNA (ribonucleic acid), each of which is a very important link for living beings.
By their chemical nature, DNA and RNA are sequences of nucleotides linked by hydrogen bonds and phosphate bridges. The composition of the DNA includes nucleotides such as:
- adenine;
- thymine;
- guanine;
- cytosine;
- five carbon sugar deoxyribose.
RNA is distinguished by the fact that thymine is replaced by uracil, and sugar - by ribose.
Due to the special structural organization of the DNA molecule capable of performing a number of vital functions. RNA also plays a large role in the cell.
Functions of such acids
Nucleic acids are biopolymers responsible for the following functions:
- DNA is the guardian and transmittergenetic information in the cells of living organisms. In prokaryotes, this molecule is distributed in the cytoplasm. In a eukaryotic cell is located inside the nucleus, separated by a karyolemma.
- Двуцепочечная молекула ДНК разделена на участки - the genes that make up chromosome structures. The genes of each creature form a special genetic code in which all signs of the organism are encrypted.
- РНК бывает трех видов - матричная, рибосомальная and transport. Ribosomal is involved in the synthesis and assembly of protein molecules on the relevant structures. The matrix and transport transfer the information read from the DNA and interpret its biological meaning.
Polysaccharides
Compound data is predominantlyplant polymers, that is, found precisely in the cells of the representatives of the flora. Their cell wall, which contains cellulose, is especially rich in polysaccharides.
By their chemical nature, polysaccharides aremacromolecules of complex carbohydrates. May be linear, layered, crosslinked conformations. Monomers are simple five-, often six-carbon sugars - ribose, glucose, fructose. They are of great importance for living beings, as they are part of the cells, are a reserve nutrient of plants, are split with the release of large amounts of energy.
Value of various representatives
Such biological polymers as starch, cellulose, inulin, glycogen, chitin and others are very important. They are the most important sources of energy in living organisms.
Cellulose is an essential component of cellplant walls, some bacteria. Gives strength, a certain shape. In industry, man is used to produce paper, valuable acetate fibers.
Starch is a plant nutrient reserve that is also a valuable food for humans and animals.
Glycogen, or animal fat, is a reserve nutrient of animals and humans. It performs the functions of thermal insulation, energy source, mechanical protection.
Mixed biopolymers in the composition of living beings
Besides those that we have reviewed, there arevarious combinations of high molecular weight compounds. Such biopolymers are complex mixed constructs of proteins and lipids (lipoproteins) or of polysaccharides and proteins (glycoproteins). A combination of lipids and polysaccharides (lipopolysaccharides) is also possible.
Each of these biopolymers has manyspecies that perform a number of important functions in living beings: transport, signaling, receptor, regulatory, enzymatic, construction, and many others. Their structure is very complex chemically and is far from being deciphered for all representatives, therefore, the functions are not fully defined. At present, only the most common are known, but a significant part remains outside the boundaries of human knowledge.
