For the human body, as well as other living beings, energy is needed. Without it, no processes can take place. After all, every biochemical reaction, every enzymatic process or stage of metabolism needs an energy source.
Therefore, the importance of substances that provide the body with strength for life is very large and important. What are these substances? Carbohydrates, proteins, fats. The structure of each of them is different, they belong to completely different classes of chemical compounds, but one of their functions is similar - providing the body with the necessary energy for life. Consider one group of the listed substances - carbohydrates.
Classification of carbohydrates
The composition and structure of carbohydrates since their discovery was determined by their name. Indeed, according to early sources, it was believed that this is a group of compounds in the structure of which there are carbon atoms associated with water molecules.
A more thorough analysis, as well as the accumulated information about the diversity of these substances, made it possible to prove that not all representatives have only such a composition. Howeverthis feature is still one of those that determine the structure of carbohydrates.
The modern classification of this group of compounds is as follows:
- Monosaccharides (ribose, fructose, glucose, etc.).
- Oligosaccharides (bioses, trioses).
- Polysaccharides (starch, cellulose).
Also, all carbohydrates can be divided into the following two large groups:
- restoring;
- non-restorative.
The structure of carbohydrate molecules of each group will be considered in more detail.
Monosaccharides: characteristics
This category includes all simple carbohydrates that contain an aldehyde (aldoses) or ketone (ketoses) group and no more than 10 carbon atoms in the chain structure. If you look at the number of atoms in the main chain, then monosaccharides can be divided into:
- trioses (glyceraldehyde);
- tetroses (erythrulose, erythrose);
- pentoses (ribose and deoxyribose);
- hexoses (glucose, fructose).
All other representatives are not as important for the body as those listed.
Features of the structure of molecules
According to their structure, monoses can be presented both in the form of a chain and in the form of a cyclic carbohydrate. How does this happen? The thing is that the central carbon atom in the compound is an asymmetric center around which the molecule in solution is able to rotate. This is how optical isomers of L- and D-form monosaccharides are formed. Whereinthe glucose formula, written in the form of a straight chain, can be mentally grasped by the aldehyde group (or ketone) and rolled into a ball. The corresponding cyclic formula will be obtained.
The chemical structure of carbohydrates of the monoz series is quite simple: a number of carbon atoms forming a chain or cycle, from each of which hydroxyl groups and hydrogen atoms are located on different or on the same side. If all structures of the same name are on one side, then a D-isomer is formed, if they are different with alternation of each other, then an L-isomer is formed. If we write down the general formula of the most common representative of glucose monosaccharides in molecular form, then it will look like: . Moreover, this record reflects the structure of fructose too. After all, chemically, these two monoses are structural isomers. Glucose is an aldehyde alcohol, fructose is a keto alcohol.
The structure and properties of carbohydrates of a number of monosaccharides are closely interrelated. Indeed, due to the presence of aldehyde and ketone groups in the composition of the structure, they belong to aldehyde and keto alcohols, which determines their chemical nature and the reactions in which they are able to enter.
Thus, glucose exhibits the following chemical properties:
1. Reactions due to the presence of a carbonyl group:
- oxidation - "silver mirror" reaction;
- with freshly precipitated copper (II) hydroxide - aldonic acid;
- strong oxidizing agents are able to form dibasic acids (aldaric), converting not only the aldehyde, but also one hydroxyl group;
- recovery - converted to polyhydric alcohols.
2. The molecule also contains hydroxyl groups, which reflects the structure. Carb properties affected by grouping data:
- ability to alkylate - the formation of ethers;
- acylation - formation of esters;
- qualitative reaction for copper (II) hydroxide.
3. Highly specific properties of glucose:
- butyric;
- alcohol;
- lactic acid fermentation.
Functions performed in the body
The structure and function of carbohydrates of the monoses series are closely related. The latter consist, first of all, in participation in the biochemical reactions of living organisms. What role do monosaccharides play in this?
- Basis for the production of oligo- and polysaccharides.
- Pentoses (ribose and deoxyribose) are the most important molecules involved in the formation of ATP, RNA, DNA. And they, in turn, are the main suppliers of hereditary material, energy and protein.
- The concentration of glucose in human blood is a true indicator of osmotic pressure and its changes.
Oligosaccharides: structure
The structure of carbohydrates of this group is reduced to the presence of two (dioses) or three (trioses) molecules of monosaccharides in the composition. There are also those that include 4, 5 or more structures (up to 10), but the most common are disaccharides. That is, during hydrolysiscompounds break down to form glucose, fructose, pentose, and so on. What compounds fall into this category? A typical example is sucrose (common cane sugar), lactose (the main component of milk), m altose, lactulose, isom altose.
The chemical structure of carbohydrates of this series has the following features:
- General molecular species formula: C12H22O11.
- Two identical or different monose residues in the disaccharide structure are interconnected by a glycosidic bridge. The nature of this compound will determine the reducing ability of sugar.
- Reducing disaccharides. The structure of carbohydrates of this type consists in the formation of a glycosidic bridge between the hydroxyl of the aldehyde and hydroxyl groups of different monos molecules. These include: m altose, lactose, and so on.
- Non-reducing - a typical example of sucrose - when a bridge is formed between the hydroxyls of only the corresponding groups, without the participation of the aldehyde structure.
Thus, the structure of carbohydrates can be briefly represented as a molecular formula. If a detailed detailed structure is needed, then it can be depicted using Fisher's graphic projections or Haworth's formulas. Specifically, two cyclic monomers (monoses) are either different or identical (depending on the oligosaccharide), interconnected by a glycosidic bridge. When building, the restoring ability should be taken into account for the correct display of the connection.
Examples of disaccharide molecules
If the task is in the form: "Mark the structural features of carbohydrates", then for disaccharides it is best to first indicate what residues of monoz it consists of. The most common types are:
- sucrose - built from alpha-glucose and beta-fructose;
- m altose - from glucose residues;
- cellobiose - consists of two D-form beta-glucose residues;
- lactose - galactose + glucose;
- lactulose - galactose + fructose and so on.
Then, according to the available residues, a structural formula should be drawn up with a clear indication of the type of glycosidic bridge.
Importance for living organisms
The role of disaccharides is also very important, not only the structure is important. The functions of carbohydrates and fats are generally similar. The basis is the energy component. However, for some individual disaccharides, their specific meaning should be given.
- Sucrose is the main source of glucose in the human body.
- Lactose is found in the breast milk of mammals, including up to 8% in women's milk.
- Lactulose is obtained in a laboratory for medical use and added to dairy products.
Any disaccharide, trisaccharide and so on in the human body and other creatures undergoes instant hydrolysis to form monoses. It is this feature that underlies the use of this class of carbohydrates by humans in their raw, unchanged form (beet or cane sugar).
Polysaccharides: features of molecules
The functions, composition and structure of carbohydrates of this series are of great importance for organisms of living beings, as well as for human economic activity. First, you should figure out which carbohydrates are polysaccharides.
There are a lot of them:
- starch;
- glycogen;
- murein;
- glucomannan;
- cellulose;
- dextrin;
- galactomannan;
- muromin;
- pectic substances;
- amylose;
- chitin.
This is not a complete list, but only the most significant for animals and plants. If you perform the task "Mark the structural features of carbohydrates of a number of polysaccharides", then first of all you should pay attention to their spatial structure. These are very voluminous, gigantic molecules, consisting of hundreds of monomer units cross-linked by glycosidic chemical bonds. Often the structure of polysaccharide carbohydrate molecules is a layered composition.
There is a certain classification of such molecules.
- Homopolysaccharides - consist of the same repeatedly repeating units of monosaccharides. Depending on the monoses, they can be hexoses, pentoses, and so on (glucans, mannans, galactans).
- Heteropolysaccharides - formed by different monomer units.
Compounds with a linear spatial structure should include, for example, cellulose. Most polysaccharides have a branched structure - starch, glycogen, chitin and so on.
Role in the body of living beings
The structure and functions of this group of carbohydrates are closely related to the vital activity of all creatures. So, for example, plants in the form of a reserve nutrient accumulate starch in different parts of the shoot or root. The main source of energy for animals is again polysaccharides, the breakdown of which produces quite a lot of energy.
Carbohydrates play a very significant role in the structure of the cell. The cover of many insects and crustaceans consists of chitin, murein is a component of the bacterial cell wall, cellulose is the basis of plants.
The reserve nutrient of animal origin is glycogen molecules, or, as it is more commonly called, animal fat. It is stored in separate parts of the body and performs not only an energy, but also a protective function against mechanical influences.
For most organisms, the structure of carbohydrates is of great importance. The biology of every animal and plant is such that it requires a constant source of energy, inexhaustible. And only they can give this, and most of all in the form of polysaccharides. So, the complete breakdown of 1 g of carbohydrate as a result of metabolic processes leads to the release of 4.1 kcal of energy! This is the maximum, no more connections. That is why carbohydrates must be present in the diet of any person and animal. Plants, on the other hand, take care of themselves: in the process of photosynthesis, they form starch inside themselves and store it.
General properties of carbohydrates
The structure of fats, proteins and carbohydratesgenerally similar. After all, they are all macromolecules. Even some of their functions are of a common nature. The role and importance of all carbohydrates in the life of the planet's biomass should be summarized.
- The composition and structure of carbohydrates imply their use as a building material for the shell of plant cells, animal and bacterial membranes, as well as the formation of intracellular organelles.
- Protective function. It is characteristic of plant organisms and manifests itself in the formation of thorns, spines, and so on.
- Plastic role - the formation of vital molecules (DNA, RNA, ATP and others).
- Receptor function. Polysaccharides and oligosaccharides are active participants in transport transfers through the cell membrane, "guards" that capture effects.
- The energy role is the most significant. Provides maximum energy for all intracellular processes, as well as the work of the whole organism as a whole.
- Regulation of osmotic pressure - glucose controls this.
- Some polysaccharides become a reserve nutrient, a source of energy for animal creatures.
Thus, it is obvious that the structure of fats, proteins and carbohydrates, their functions and role in the organisms of living systems are of decisive and decisive importance. These molecules are the creators of life, they also preserve and support it.
Carbohydrates with other macromolecular compounds
Also known is the role of carbohydrates not in their pure form, but in combination with other molecules. These include the most commonlike:
- glycosaminoglycans or mucopolysaccharides;
- glycoproteins.
The structure and properties of carbohydrates of this type are quite complex, because a variety of functional groups are combined into a complex. The main role of molecules of this type is participation in many life processes of organisms. Representatives are: hyaluronic acid, chondroitin sulfate, heparan, keratan sulfate and others.
There are also complexes of polysaccharides with other biologically active molecules. For example, glycoproteins or lipopolysaccharides. Their existence is important in the formation of the body's immunological reactions, since they are part of the cells of the lymphatic system.
