Chemistry distinguishes between three types of carbohydrates. This is starch, fiber and glucose. Starch is the most important representative of the group of natural carbohydrates. Its synthesis occurs in all plants, it is the main source of energy for the human body. What is a starch monomer? About it below.
Fields of application
Since a very long time, starch is widely used in the field of medicine. In medical practice, it is used as an enveloping agent for ulcerative lesions and inflammatory processes of the mucous membrane of organs such as the intestines and stomach. Analytical and pharmaceutical chemistry uses starch as a major indicator of iodine. Pharmaceutical technology uses starch as a bulking agent. But what compound is the monomer of starch is interesting to many. We will understand in this article.
The only scientific center for starch industry in our country is represented by the All-Russian Research Institute of Starch Products. It is located in the Moscow region, and its main task is to develop new technologies for producing starch from cereals and potatoes, modified starch, glucose and molasses, glucose-fructose syrups and dietary products without protein. In addition to research activities, VNIIK is engaged in the design of specialized equipment that is used in the starch industry. Thus, the activities of VNIIK affect a large scientific field: from conducting research to industrial development.
Below we consider what is the monomer of starch.
Structure
If we consider starch from the point of view of science, then it represents a huge number of simple sugars that are collected in a chain. Such chains may be linear or branched. The main molecule of each such chain is glucose, which is the substance that is assigned the role of the main source of energy in the human body.
Any such long chain, consisting of glucose, has the property of bending, wriggling and folding repeatedly. As a result of this, the formation of microscopic granules that look like flour grains. By the way, flour is essentially a mixture consisting of starch and various related substances. That is, the starch monomer is glucose.
If you take the starch in your hand and try to squeeze it in a fist and grind it between your fingers, you will hear a specific creak. A similar sound arises in the process of friction of starch particles against each other: they have a solid structure, and destruction under such an impact does not occur.
In plant organisms, starch is formed as a result of the serial connection of a sufficiently large number of glucose molecules. Before this, glucose is synthesized from carbon dioxide and water. After all, it is a monomer of a starch molecule.
Starch properties
In most plants, starch is the main accumulator of energy reserves. It is with this property that one can explain that the most active starch storage occurs in roots, tubers and seeds. By composition, wheat or corn grain is more than half starch.
Let us consider in more detail the chemical composition and structure of starch. Starch, along with glycogen and cellulose, is one of the most important representatives of the polysaccharide group.
Polysaccharides
Polysaccharides are substances that are carbohydrate polymers that consist of a huge amount of monosaccharide units. Their number can vary from several tens to several thousand. That is, it is a high molecular weight compound (IUD), and glucose is the starch monomer.
General formula
The general formula for macromolecular compounds can be written as follows:
(C 6 H 10 O 5 ) n, where n in this case can reach hundreds and thousands.
Outwardly, starch is known to everyone - it is a white substance that consists of small grains. Starch is not soluble in cold water, but soluble in hot. It has the property of swelling. The resulting solutions of viscous consistency after cooling go into a gelatinous mass, called a paste.
The starch contains two fractions: amylopectin and amylose. These two fractions are formed by α-D-glucose. They differ among themselves not only in the structure of the chain itself, but also in the number of glucose residues. These monosaccharide residues are interconnected by oxygen bridges. In the process of chain formation, the interaction of the glycosidic hydroxyl of one molecule and the alcohol hydroxyl of another molecule occurs. When starch interacts with an iodine solution, a characteristic blue color appears. That is, the reaction is of a qualitative nature. Staining disappears if the solution is heated, and occurs if it is cooled.
Now it is clear which compound is the monomer of starch.
Amylose is a polysaccharide with a linear chemical chain, it is built from several thousand hexoses (glucose residues), which are interconnected by an α-glycosidic bond. X-ray diffraction analysis indicates that the amylose molecule has a helical arrangement. In each coil of the spiral there are exactly 6 units formed by monosaccharides. On average, there are about 50 turns in such a spiral.
Inside such a spiral structure there is a channel with a diameter of about 0.5 nanometers. Other molecules that are suitable in size may be located inside the channel. This design represents special complexes, which are called inclusion compounds. The amylose-iodine compound, which has a blue color, is just one of these structures. What is the monomer of starch, we found out earlier.
Amylose and Amylopectin
Amylose and amylopectin have exactly the same chemical composition, the main difference between them is the spatial structure. The amylose molecule is thread-like, i.e. linear, and the amylopectin molecule has a branched structure.
Between the branch points, approximately 20-25 hexoses are located. In total, the amylopectin macromolecule may contain about 6,000 or more units formed by monosaccharides.
As a rule, 10-20% starch consists of bound water. If it is heated quickly, then hydrolytic decomposition of macromolecules will occur, and as a result, smaller chains of molecules will form.
Starch is the main source of carbohydrates in the human diet, which is why it is of the greatest importance in the form of food products: bread, potatoes, cereals. In large quantities, starch is used in industry, for example, it is used for sizing fabrics (in the process of sizing), for gluing paper and cardboard, and for the production of dextrin glue. In the field of analytical chemistry, starch is used as an indicator during the iodometric titration method.
We found out which substance is the monomer of starch.