A huge number of various compounds of various chemical nature managed to synthesize people in the laboratory. However, all the same, natural substances were, are and will remain the most important and significant for the life of all living systems. That is, those molecules that are involved 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".
General concept of biopolymers
First of all, it should be said that all these compounds are high-molecular, having a mass reaching millions of D altons. These substances are animal and plant polymers that play a decisive role in building cells and their structures, ensuring metabolism, photosynthesis, respiration, nutrition and all other vital functions of any living organism.
It is difficult to overestimate the importance 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 are the specific connections to thembelong?
Cell biopolymers
There are a lot of them. So, the main biopolymers are as follows:
- proteins;
- polysaccharides;
- nucleic acids (DNA and RNA).
In addition to them, this also includes many mixed polymers formed from combinations of those already listed. 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 monomeric link;
- 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.
Proteins
Protein molecules are of great importance in the life of any living beings. 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 order in the structure. Each protein is made up of amino acid residues thatable to connect to each other in unlimited chain lengths. This happens 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 the same and different (several tens of thousands or more). In total, there are 20 varieties 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 as a primary, secondary, tertiary or quaternary structure.
The most simple and linear of them is the primary one. It is simply a series of amino acid sequences connected to each other.
The secondary conformation has a more complex structure, as the overall macrochain of the protein begins to spiral, forming coils. Two adjacent macrostructures are held near each other due to covalent and hydrogen interactions between the groups of their atoms. Distinguish between alpha and beta helices of the secondary structure of proteins.
The tertiary structure is a single macromolecule (polypeptide chain) of a protein rolled into a ball. A very complex network of interactions within this globule allows it to be quite stable and keep its shape.
Quaternary conformation - a few polypeptide chains, coiled and twistedinto a coil, 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 protein cells that make up the plasma membrane. They form ion channels through which certain molecules are able to pass. Also, many proteins are part of the organelles 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 building 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 (cytoskeleton of the cytoplasm, plasma membrane, ribosome, mitochondria and other structures take part 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, as they are biological catalysts in living systems.
- Receptor (also signaling) function helps cells navigate and respond correctly to any changes in the environment, such asmechanical and chemical.
If we consider proteins in more depth, we can highlight some more secondary functions. However, the ones listed are the main ones.
Nucleic acids
Such biopolymers are an important part of every cell, be it prokaryotic or eukaryotic. Indeed, nucleic acids include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) molecules, each of which is a very important link for living beings.
By their chemical nature, DNA and RNA are sequences of nucleotides connected by hydrogen bonds and phosphate bridges. DNA is composed of nucleotides such as:
- adenine;
- thymine;
- guanine;
- cytosine;
- 5-carbon sugar deoxyribose.
RNA is different in that thymine is replaced by uracil, and sugar by ribose.
Due to the special structural organization of DNA molecules are able to perform a number of vital functions. RNA also plays a big role in the cell.
Functions of such acids
Nucleic acids are biopolymers responsible for the following functions:
- DNA is the store and transmitter of genetic information in the cells of living organisms. In prokaryotes, this molecule is distributed in the cytoplasm. In a eukaryotic cell, it is located inside the nucleus, separated by a karyolemma.
- Double-stranded DNA molecule is divided into sections - genes that make up the structure of the chromosome. Everyone's genescreatures form a special genetic code in which all signs of the organism are encrypted.
- RNA is of three types - template, ribosomal and transport. Ribosomal takes part 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 predominantly plant polymers, that is, they are found precisely in the cells of representatives of the flora. Their cell wall, which contains cellulose, is especially rich in polysaccharides.
By their chemical nature, polysaccharides are complex carbohydrate macromolecules. They can be linear, layered, cross-linked conformations. Monomers are simple five-, more often six-carbon sugars - ribose, glucose, fructose. They are of great importance for living beings, as they are part of the cells, they are a reserve nutrient for plants, they are broken down with the release of a large amount of energy.
Meaning of various representatives
Biological polymers such as starch, cellulose, inulin, glycogen, chitin and others are very important. They are the 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 plant nutrient,which is also a valuable food product for humans and animals.
Glycogen, or animal fat, is a reserve nutrient for animals and humans. Performs the functions of thermal insulation, energy source, mechanical protection.
Mixed biopolymers in living beings
In addition to those that we have considered, there are various combinations of macromolecular compounds. Such biopolymers are complex mixed structures of proteins and lipids (lipoproteins) or 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 beings: 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.
