Polymerization: Function, Tasks, Role & Diseases

A polymerization characterizes the formation of polymers from monomers. In chemistry and biology, there are different types of polymerizations. In organisms, polymerization reactions take place to form biopolymers such as proteins, nucleic acids, or polysaccharides.

What is polymerization?

Polymerization reactions take place in organisms to form biopolymers such as proteins or nucleic acids. Nucleic acids are components of DNA and RNA. Polymerization is a collective term for the formation of polymers from low molecular weight monomers. Polymerization reactions play a major role in both chemistry and biology. Polymers are high-molecular substances that consist of certain basic building blocks. These basic building blocks, also called monomers, accumulate during polymerization and form high-molecular chains. Polymers can be composed of the same or different monomers. In chemistry, for example, polyester, polyethylene, polyvinyl chloride (PVC) or other plastics are known as polymers. In biology, proteins, nucleic acids or polysaccharides represent highly complex biopolymers. In the chemical field, there are different types of polymerization reactions. Chain growth reactions and step growth reactions are distinguished. In chain growth reactions, after an initial reaction, further monomers constantly bind to the activated chain. This leads to chain growth. In step growth reactions, the monomers involved must have at least two functional groups. There is no continuous chain growth, but dimers, trimers or oligomers are formed first, which later combine to form a longer chain. Typical step growth reactions take the form of addition or condensation reactions. However, the formation of biopolymers in biological systems is much more complicated. It requires many different reaction steps. For example, the formation of proteins or nucleic acids only takes place with the help of templates. In the genetic code, the sequence of the nitrogen bases in the nucleic acids is specified. These, in turn, code the sequence of amino acids in the individual proteins.

Function and task

Polymerizations play a prominent role in all biological systems of bacteria, fungi, plants, and animals (including humans). Thus, proteins and nucleic acids are the prerequisite for life in the first place. In essence, the polymerization reactions to form these biomolecules and their degradation are the actual reactions of life. Nucleic acids are components of DNA and RNA. They are composed of phosphoric acid, a monosugar (deoxyribose or ribose), and four nitrogenous bases. Phosphoric acid, sugar and a nitrogen base are each assembled to form a nucleotide. The nucleic acids, in turn, consist of chains of nucleotides arranged in a row. DNA contains deoxyribose and RNA contains ribose as a sugar molecule. The individual nucleotides differ only in their nitrogen base. Three consecutive nucleotides each code for one amino acid as a triplet. Thus, the sequence of the nucleotides represents the genetic code. The genetic code laid down in the DNA is transferred to the RNA via complicated mechanisms. The RNA is then in turn responsible for the synthesis of proteins with a fixed amino acid sequence. Certain sections in the DNA (genes) thus code for the corresponding proteins. Each protein has a specific function in the organism. Thus, there are muscle proteins, proteins of the connective tissue, immunoglobulins, peptide hormones or enzymes. In turn, a special enzyme with a specific composition is responsible for each metabolic step. This already shows how important precisely coordinated polymerization reactions for building nucleic acids and proteins are for the smooth biochemical processes in the organism. For example, the enzymes must have the correct amino acid sequence in order to be able to catalyze the specific reaction step in the metabolism for which they are responsible. In addition to proteins and nucleic acids, polysaccharides are also important biopolymers in the organism. In plants, they often perform supporting functions. Furthermore, they also store energy. Starch in potatoes, for example, is a reserve substance that is used to generate energy during sprouting.Humans also store glycogen in the liver and muscles to meet energy needs during periods of food restriction or intense physical activity. Glycogen, like starch, is a polymer and is formed from the monomer glucose.

Diseases and ailments

Disruptions in biological polymerization reactions can lead to significant health problems. As mentioned earlier, nucleic acids are important biopolymers. When chemical processes alter the sequence of certain nitrogenous bases, a so-called mutation is present. The mutated gene continues to encode proteins, but their amino acid order changes. The proteins altered in this way can no longer fulfill their function properly in the affected cells. This can lead to metabolic disorders, since an enzyme may fail. However, the immunoglobulins may also be altered. In this case, immunodeficiencies occur. Of course, structural proteins can also be affected by the changes, with many different manifestations and symptoms. The mutations are often also passed on to the offspring. In the course of life, errors in the reproduction of the genetic code occur again and again. In most cases, the affected body cells are destroyed by the immune system. However, this is not always successful. In some cases, these cells develop into cancer cells, for example, and their growth threatens the entire organism. Many other degenerative diseases, such as arteriosclerosis, rheumatic complaints or autoimmune diseases, can also be traced back to disturbances in the synthesis of biopolymers. Even the synthesis of glycogen, the polysaccharide in the liver and muscles, can be defective. For example, there are glycogen storage diseases with abnormally altered glycogen molecules, which in turn can be caused by defective enzymes. The abnormal glycogen can no longer be broken down and continues to accumulate in the liver.