A huge number of various compounds of various chemical nature man was able to synthesize in laboratory conditions. However, all the same, the most important and significant for the life of all living systems were, are and will remain just 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 the group called "biological polymers".
The general concept of biopolymers
First of all, it should be said that all these compounds are high molecular weight, with a mass reaching millions of Daltons. These substances are animal and plant polymers that play a decisive role in the construction of cells and their structures, the provision of metabolism, photosynthesis, respiration, nutrition and all other vital functions of any living organism.
It is difficult to overestimate the value of such compounds. Biopolymers are natural substances of natural origin that form in living organisms and are the basis of all life on our planet. What specific compounds relate to them?
Cell biopolymers
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 combinations of those already listed can also be attributed here. For example, lipoproteins, lipopolysaccharides, glycoproteins and others.
General properties
There are several features that are inherent in all considered molecules. For example, the following general properties of biopolymers:
- large molecular weight due to the formation of huge macrochains with branches in the chemical structure;
- types of bonds in macromolecules (hydrogen, ionic interactions, electrostatic attraction, disulfide bridges, peptide bonds and others);
- 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 function than similarities.
Squirrels
Of great importance in the life of any living creatures are protein molecules. Such biopolymers are the basis of all biomass. Indeed, even according to the Oparin-Haldane theory, life on Earth originated from a coacervate droplet, which was a protein.
The structure of these substances is subject to strict ordering in the structure. The basis of each protein is amino acid residues that are able to bind to each other in an unlimited chain length. This occurs through the formation of special bonds — peptide bonds. Such a bond is formed between four elements: carbon, oxygen, nitrogen and hydrogen.
A protein molecule can contain a lot of amino acid residues, both identical and different (several tens of thousands or more). There are 20 types of amino acids in the composition of these compounds. However, their diverse combination allows proteins to flourish in quantitative and species terms.
Protein biopolymers have different spatial conformations. So, each representative can exist in the form of a primary, secondary, tertiary or quaternary structure.
The simplest and most linear of them is primary. It is simply a series of amino acid sequences linked together.
The secondary conformation is characterized by a more complex structure, since the general macrochain of the protein begins to spiral, forming coils. Two adjacent macrostructures are held near each other due to covalent and hydrogen interactions between groups of their atoms. There are alpha and beta helices of the secondary structure of proteins.
The tertiary structure is a single macromolecule (polypeptide chain) of a protein folded into a ball. A very complex network of interactions within a given globule allows it to be quite stable and keep its shape.
The quaternary conformation is a few polypeptide chains folded spirally and twisted into a ball, which also form multiple bonds of various types among themselves. The most complex globular structure.
The functions of protein molecules
- Transport. It is carried out by protein cells included in the plasma membrane. They form the ion channels through which certain molecules are able to pass. Also, many proteins are part of the organoids of the movement of protozoa and bacteria, therefore, they are directly involved in their movement.
- The energy function is performed by these molecules very actively. 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 construction function is the participation of protein molecules in the construction of most cellular structures, the cells themselves, tissues, organs, and so on. Almost any cell is basically built from these molecules (cytoplasm of the cytoplasm, plasma membrane, ribosome, mitochondria and other structures involved in the formation of protein compounds).
- The catalytic function is carried out by enzymes, which 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.
- The receptor (also signaling) function helps cells to navigate and properly respond to any changes in the environment, both mechanical and chemical.
If we consider proteins in more depth, we can distinguish some more secondary functions. However, these are the main ones.
Nucleic acids
Such biopolymers are an important part of every cell, be it prokaryotic or eukaryotic. Indeed, the nucleic acids include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) molecules, each of which is a very important link for living things.
By their chemical nature, DNA and RNA are nucleotide sequences connected by hydrogen bonds and phosphate bridges. The composition of DNA includes nucleotides such as:
- adenine;
- thymine;
- guanine;
- cytosine;
- five-carbon sugar deoxyribose.
RNA is different in that thymine is replaced by uracil, and sugar by ribose.
Due to the special structural organization, DNA molecules are able to perform a number of vital functions. RNA also plays a large role in the cell.
The functions of such acids
Nucleic acids are biopolymers responsible for the following functions:
- DNA is the custodian and transmitter of genetic 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 karyolemma.
- The double-stranded DNA molecule is divided into sections - genes that make up the structure of the chromosome. The genes of each creature form a special genetic code in which all the signs of the body are encrypted.
- RNA is of three types - matrix, ribosomal and transport. Ribosomal is involved in the synthesis and assembly of protein molecules on the corresponding structures. Matrix and transport transfer information read from DNA and decipher its biological meaning.
Polysaccharides
These compounds are mainly plant polymers, that is, found specifically in the cells of flora representatives. Their cell wall, which contains cellulose, is especially rich in polysaccharides.
By their chemical nature, polysaccharides are macromolecules of complex carbohydrates. May be linear, layered, stitched conformations. Monomers are simple five-, often six-carbon sugars - ribose, glucose, fructose. They are of great importance for living creatures, as they are part of the cells, are a reserve nutrient of plants, and are split with the release of a large amount of energy.
The value of various representatives
Biological polymers such as starch, cellulose, inulin, glycogen, chitin and others are very important. It is they who are important sources of energy in living organisms.
So, cellulose is an essential component of the cell wall of plants, some bacteria. Gives strength, a certain shape. In industry, man is used to obtain paper, valuable acetate fibers.
Starch is a reserve nutrient of plants, which is also a valuable food product for humans and animals.
Glycogen, or animal fat, is a reserve nutrient in animals and humans. It performs the functions of thermal insulation, energy source, mechanical protection.
Mixed biopolymers in living beings
In addition to those that we examined, there are various combinations of high molecular weight compounds. Such biopolymers are complex mixed designs from proteins and lipids (lipoproteins) or from polysaccharides and proteins (glycoproteins). A combination of lipids and polysaccharides (lipopolysaccharides) is also possible.
Each of these biopolymers has many varieties that perform a number of important functions in living things: transport, signaling, receptor, regulatory, enzymatic, building, and many others. Their structure is chemically very complex and far from being deciphered for all representatives; therefore, the functions are not fully defined. Today, only the most common are known, but a significant part remains beyond the boundaries of human knowledge.