All carbohydrates are made up of individual “units”, which are saccharides. Based on their ability to hydrolyze into monomers, carbohydrates are divided into two groups: simple and complex. Carbohydrates containing one unit are called monosaccharides, two units are called disaccharides, two to ten units are called oligosaccharides, and more than ten units are called polysaccharides. Monosaccharides quickly increase blood sugar and have a high glycemic index, which is why they are also called fast carbohydrates. They easily dissolve in water and are synthesized in green plants. Carbohydrates made up of 3 or more units are called complex carbohydrates. Foods rich in complex carbohydrates gradually increase glucose levels and have a low glycemic index, which is why they are also called slow carbohydrates. Complex carbohydrates are products of polycondensation of simple sugars (monosaccharides) and, unlike simple ones, during the process of hydrolytic cleavage they can decompose into monomers with the formation of hundreds and thousands of monosaccharide molecules.
A common monosaccharide in nature is beta-D-glucose.
Monosaccharides
Monosaccharides (from the Greek monos - single, sacchar - sugar) - the simplest carbohydrates that do not hydrolyze to form simpler carbohydrates - are usually colorless, easily soluble in water, poorly soluble in alcohol and completely insoluble in ether, solid transparent organic compounds, one of the main groups of carbohydrates, the simplest form of sugar. Aqueous solutions have a neutral pH. Some monosaccharides have a sweet taste. Monosaccharides contain a carbonyl (aldehyde or ketone) group, so they can be considered as derivatives of polyhydric alcohols. A monosaccharide with a carbonyl group at the end of the chain is an aldehyde and is called an aldose. At any other position of the carbonyl group, the monosaccharide is a ketone and is called ketose. Depending on the length of the carbon chain (from three to ten atoms), trioses, tetroses, pentoses, hexoses, heptoses, and so on are distinguished. Among them, pentoses and hexoses are the most widespread in nature. Monosaccharides are the building blocks from which disaccharides, oligosaccharides and polysaccharides are synthesized.
In nature, the most common free form is D-glucose (C6H12O6) - a structural unit of many disaccharides (maltose, sucrose and lactose) and polysaccharides (cellulose, starch). Other monosaccharides are mainly known as components of di-, oligo- or polysaccharides and are rarely found in the free state. Natural polysaccharides serve as the main sources of monosaccharides.
All carbohydrates are made up of individual “units”, which are saccharides. According to abilityhydrolysisonmonomerscarbohydrates are dividedinto two groups: simple and complex. Carbohydrates containing one unit are calledmonosaccharides, two units -disaccharides, from two to ten units –oligosaccharides, and more than ten -polysaccharides.
Monosaccharides They quickly increase blood sugar and have a high glycemic index, which is why they are also called fast carbohydrates. They easily dissolve in water and are synthesized in green plants.
Carbohydrates made up of 3 or more units are calledcomplex. Foods rich in complex carbohydrates gradually increase glucose levels and have a low glycemic index, which is why they are also called slow carbohydrates. Complex carbohydrates are products of polycondensation of simple sugars (monosaccharides) and, unlike simple ones, in the process of hydrolytic cleavage they can decompose into monomers, forming hundreds and thousandsmoleculesmonosaccharides.
Stereoisomerism of monosaccharides: isomerglyceraldehydein which, when projecting the model onto a plane, the OH group at the asymmetric carbon atom is located on the right side is usually considered to be D-glyceraldehyde, and the mirror image is considered to be L-glyceraldehyde. All isomers of monosaccharides are divided into D- and L-forms based on the similarity of the location of the OH group at the last asymmetric carbon atom near CH 2 OH groups (ketoses contain one less asymmetric carbon atom than aldoses with the same number of carbon atoms). Naturalhexoses – glucose, fructose, mannoseAndgalactose– according to their stereochemical configurations they are classified as D-series compounds.
Polysaccharides – the general name of a class of complex high-molecular carbohydrates,moleculeswhich consist of tens, hundreds or thousandsmonomers – monosaccharides. From the point of view of the general principles of structure in the group of polysaccharides, it is possible to distinguish between homopolysaccharides synthesized from the same type of monosaccharide units and heteropolysaccharides, which are characterized by the presence of two or more types of monomeric residues.
https :// ru . wikipedia . org / wiki /Carbohydrates
1.6. Lipids - nomenclature and structure. Lipid polymorphism.
Lipids – a large group of natural organic compounds, including fats and fat-like substances. Simple lipid molecules are composed of alcohol andfatty acids, complex - from alcohol, high-molecular fatty acids and other components.
Classification of lipids
Simple lipids are lipids that include carbon (C), hydrogen (H) and oxygen (O) in their structure.
Complex lipids are lipids that include in their structure, in addition to carbon (C), hydrogen (H) and oxygen (O), other chemical elements. Most often: phosphorus (P), sulfur (S), nitrogen (N).
https:// ru. wikipedia. org/ wiki/Lipids
Literature:
1) Cherkasova L. S., Merezhinsky M. F., Metabolism of fats and lipids, Minsk, 1961;
2) Markman A.L., Chemistry of lipids, c. 12, Tash., 1963 – 70;
3) Tyutyunnikov B.N., Chemistry of fats, M., 1966;
4) Mahler G., Cordes K., Fundamentals of Biological Chemistry, trans. from English, M., 1970.
1.7. Biological membranes. Forms of lipid aggregation. The concept of the liquid crystalline state. Lateral diffusion and flip flop.
Membranes They delimit the cytoplasm from the environment, and also form the shells of nuclei, mitochondria and plastids. They form a labyrinth of endoplasmic reticulum and stacked flattened vesicles that make up the Golgi complex. Membranes form lysosomes, large and small vacuoles of plant and fungal cells, and pulsating vacuoles of protozoa. All these structures are compartments (compartments) intended for certain specialized processes and cycles. Therefore, without membranes the existence of a cell is impossible.
Membrane structure diagram: a – three-dimensional model; b – planar image;
1 – proteins adjacent to the lipid layer (A), immersed in it (B) or penetrating it through (C); 2 – layers of lipid molecules; 3 – glycoproteins; 4 – glycolipids; 5 – hydrophilic channel, functioning as a pore.
The functions of biological membranes are as follows:
1) They delimit the contents of the cell from the external environment and the contents of organelles from the cytoplasm.
2) Provide transport of substances into and out of the cell, from the cytoplasm to organelles and vice versa.
3) Act as receptors (receiving and converting signals from the environment, recognizing cell substances, etc.).
4) They are catalysts (providing near-membrane chemical processes).
5) Participate in energy conversion.
http:// sbio. info/ page. php? id=15
Lateral diffusion is the chaotic thermal movement of lipid and protein molecules in the plane of the membrane. During lateral diffusion, nearby lipid molecules change places abruptly, and as a result of such successive jumps from one place to another, the molecule moves along the surface of the membrane.
The movement of molecules along the surface of the cell membrane over time t was determined experimentally by the method of fluorescent labels - fluorescent molecular groups. Fluorescent labels make molecules fluoresce, the movement of which along the cell surface can be studied, for example, by studying under a microscope the rate at which a fluorescent spot created by such molecules spreads over the cell surface.
Flip flop is the diffusion of membrane phospholipid molecules across the membrane.
The speed of molecules jumping from one surface of the membrane to another (flip-flop) was determined by the spin label method in experiments on model lipid membranes - liposomes.
Some of the phospholipid molecules from which liposomes were formed were labeled with spin labels attached to them. Liposomes were exposed to ascorbic acid, as a result of which unpaired electrons on the molecules disappeared: paramagnetic molecules became diamagnetic, which could be detected by a decrease in the area under the EPR spectrum curve.
Thus, jumps of molecules from one surface of the bilayer to another (flip-flop) occur much more slowly than jumps during lateral diffusion. The average time after which a phospholipid molecule flip-flops (T ~ 1 hour) is tens of billions of times greater than the average time characteristic of a molecule jumping from one place to another in the plane of the membrane.
The concept of the liquid crystalline state
A solid can be likecrystalline , soamorphous. In the first case, there is long-range order in the arrangement of particles at distances much greater than intermolecular distances (crystal lattice). In the second, there is no long-range order in the arrangement of atoms and molecules.
The difference between an amorphous body and a liquid is not the presence or absence of long-range order, but the nature of particle motion. Molecules of liquids and solids perform oscillatory (sometimes rotational) movements around the equilibrium position. After some average time (“settled life time”) the molecules jump to another equilibrium position. The difference is that the “settled life time” in a liquid is much less than in a solid state.
Lipid bilayer membranes under physiological conditions are liquid; the “settled life time” of a phospholipid molecule in the membrane is 10 −7 – 10 −8 With.
The molecules in the membrane are not randomly located; long-range order is observed in their arrangement. Phospholipid molecules are in a bilayer, and their hydrophobic tails are approximately parallel to each other. There is also order in the orientation of the polar hydrophilic heads.
A physiological state in which there is long-range order in the mutual orientation and arrangement of molecules, but the state of aggregation is liquid, is calledliquid crystalline state. Liquid crystals can not form in all substances, but in substances from “long molecules” (the transverse dimensions of which are smaller than the longitudinal ones). Various liquid crystal structures can exist: nematic (filamentary), when long molecules are oriented parallel to each other; smectic - molecules are parallel to each other and arranged in layers; Holistic - molecules are located parallel to each other in the same plane, but in different planes the orientation of the molecules is different.
http:// www. studfiles. ru/ preview/1350293/
Literature: ON THE. Lemeza, L.V. Kamlyuk, N.D. Lisov. “A manual on biology for those entering universities.”
1.8. Nucleic acids. Heterocyclic bases, nucleosides, nucleotides, nomenclature. Spatial structure of nucleic acids - DNA, RNA (tRNA, rRNA, mRNA). Ribosomes and the cell nucleus. Methods for determining the primary and secondary structure of nucleic acids (sequencing, hybridization).
Nucleic acids – phosphorus-containing biopolymers of living organisms, ensuring the storage and transmission of hereditary information.
Nucleic acids are biopolymers. Their macromolecules consist of repeatedly repeating units, which are represented by nucleotides. And they were logically namedpolynucleotides. One of the main characteristics of nucleic acids is their nucleotide composition. The composition of a nucleotide (a structural unit of nucleic acids) includesthree components:
– Nitrogenous base. May be pyrimidine and purine. Nucleic acids contain bases of 4 different types: two of them belong to the class of purines and two to the class of pyrimidines.
– Phosphoric acid residue.
– Monosaccharide - ribose or 2-deoxyribose. The sugar that is part of the nucleotide contains five carbon atoms, i.e. is a pentose. Depending on the type of pentose present in the nucleotide, two types of nucleic acids are distinguished– ribonucleic acids (RNA), which contain ribose, anddeoxyribonucleic acids (DNA), containing deoxyribose.
Nucleotide At its core, it is a phosphorus ester of a nucleoside.Contains nucleoside consists of two components: a monosaccharide (ribose or deoxyribose) and a nitrogenous base.
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Nitrogen bases – heterocyclicorganic compounds, derivativespyrimidineAndpurinaincluded innucleic acids. For abbreviated designations, capital Latin letters are used. Nitrogenous bases includeadenine(A),guanine(G),cytosine(C), which are found in both DNA and RNA.Timin(T) is part of DNA only, anduracil(U) occurs only in RNA.
Carbohydrates
Moving on to the consideration of organic substances, one cannot fail to note the importance of carbon for life. When entering into chemical reactions, carbon forms strong covalent bonds, sharing four electrons. Carbon atoms, connecting with each other, are able to form stable chains and rings that serve as the skeletons of macromolecules. Carbon can also form multiple covalent bonds with other carbon atoms, as well as with nitrogen and oxygen. All these properties provide a unique diversity of organic molecules.
Macromolecules, which make up about 90% of the mass of a dehydrated cell, are synthesized from simpler molecules called monomers. There are three main types of macromolecules: polysaccharides, proteins and nucleic acids; their monomers are, respectively, monosaccharides, amino acids and nucleotides.
Carbohydrates are substances with the general formula C x (H 2 O) y, where x and y are natural numbers. The name “carbohydrates” indicates that in their molecules hydrogen and oxygen are in the same ratio as in water.
Animal cells contain a small amount of carbohydrates, while plant cells contain almost 70% of the total organic matter.
Monosaccharides play the role of intermediate products in the processes of respiration and photosynthesis, participate in the synthesis of nucleic acids, coenzymes, ATP and polysaccharides, and serve as released during oxidation during respiration. Monosaccharide derivatives - sugar alcohols, sugar acids, deoxysugars and amino sugars - are important in the process of respiration, and are also used in the synthesis of lipids, DNA and other macromolecules.
Disaccharides are formed by a condensation reaction between two monosaccharides. Sometimes they are used as reserve nutrients. The most common of these are maltose (glucose + glucose), lactose (glucose + galactose) and sucrose (glucose + fructose). found only in milk.
Cellulose is also a polymer of glucose. It contains about 50% of the carbon contained in plants. In terms of total mass on Earth, cellulose ranks first among organic compounds. The shape of the molecule (long chains with protruding –OH groups) ensures strong adhesion between adjacent chains. For all their strength, macrofibrils consisting of such chains easily allow water and substances dissolved in it to pass through and therefore serve as an ideal building material for plant cell walls. Cellulose is a valuable source of glucose, but its breakdown requires the enzyme cellulase, which is relatively rare in nature. Therefore, only some animals (for example, ruminants) consume cellulose as food. The industrial importance of cellulose is also great - cotton fabrics and paper are made from this substance.
Table of contents of the topic "Water. Carbohydrates. Lipids.":Simple organic molecules often serve as starting materials for the synthesis of larger ones. macromolecules. Macromolecule is a giant molecule built from many repeating units.
Molecules built in this way are called polymers, and the units of which they are composed are called monomers. In the process of connecting individual links to each other (with the so-called condensation), water is removed.
The opposite process is polymer breakdown- carried out by hydrolysis, i.e. by adding water. There are three main types of macromolecules in living organisms: polysaccharides, proteins and nucleic acids. The monomers for them are monosaccharides and nucleotides, respectively.
Macromolecules constitute about 90% of the dry mass of cells. Polysaccharides play the role of reserve nutrients and perform structural functions, while proteins and nucleic acids can be considered as “ information molecules».
Macromolecules exist not only in living nature, but also in nonliving nature, in particular, many equipment based on macromolecules are created by man himself.
This means that in proteins and nucleic acids the sequence is important monomer units and in them it varies much more than in polysaccharides, the composition of which is usually limited to one or two different types of subunits. The reasons for this will become clear to us later. In this chapter we will consider in detail all three classes of macromolecules and their subunits. To this consideration we will also add lipids - molecules, as a rule, much smaller, but also built from simple organic molecules.
Carbohydrates
Carbohydrates are substances consisting of carbon, hydrogen and , with the general formula C x (H 2 O) y where x: and y can have different meanings. The name “carbohydrates” reflects the fact that hydrogen and oxygen are present in the molecules of these substances in the same ratio as in the water molecule (two hydrogen atoms for each oxygen atom). All carbohydrates are either aldehydes or ketones and their molecules always contain several hydroxyl groups. The chemical properties of carbohydrates are determined by these groups - aldehyde, hydroxyl and keto groups. Aldehydes, for example, are easily oxidized and therefore are powerful reducing agents. The structure of these groups is presented in the table.
Carbohydrates are divided into three main classes: monosaccharides, disaccharides and polysaccharides.
Cells contain many organic compounds: carbohydrates, proteins, lipids, nucleic acids and other compounds that are not found in inanimate nature. Organic substances are chemical compounds that contain carbon atoms.
Carbon atoms are able to form strong covalent bonds with each other, forming many different chain or ring molecules.
The simplest carbon-containing compounds are hydrocarbons—compounds that contain only carbon and hydrogen. However, most organic, i.e. carbon, compounds also contain other elements (oxygen, nitrogen, phosphorus, sulfur).
Biological polymers (biopolymers). Biological polymers are organic compounds that are part of the cells of living organisms and their metabolic products.
A polymer (from the Greek “poly” - many) is a multi-link chain in which a link is some relatively simple substance - a monomer. Monomers, connecting with each other, form chains consisting of thousands of monomers. If you designate the type of monomer with a certain letter, for example A, then the polymer can be depicted as a very long combination of monomer units: A—A—A—A—...—A. These are, for example, the organic substances you know: starch, glycogen, cellulose, etc. Biopolymers are proteins, nucleic acids, and polysaccharides.
The properties of biopolymers depend on the structure of their molecules: on the number and variety of monomer units that form the polymer.
If you combine two types of monomers A and B together, you can get a very large variety of polymers. The structure and properties of such polymers will depend on the number, ratio and order of alternation, i.e., the position of monomers in the chains. A polymer in the molecule of which a group of monomers repeats periodically is called regular. These are, for example, schematically depicted polymers with a regular alternation of monomers:
A B A B A B A B...
A A B B A A B B...
A B B A B B A B B A B B...
However, it is possible to obtain much more variants of polymers in which there is no visible pattern in the repeatability of monomers. Such polymers are called irregular. Schematically they can be depicted as follows:
AABABBBBAAAAABBABBBBBAAB...
Let us assume that each of the monomers determines some property of the polymer. For example, monomer A determines high strength, and monomer B determines electrical conductivity. By combining these two monomers in different proportions and alternating them in different ways, a huge number of polymer materials with different properties can be obtained. If we take not two types of monomers (A and B), but more, then the number of variants of polymer chains will increase significantly.
It turned out that the combination and rearrangement of several types of monomers in long polymer chains provides the construction of many options and determines the various properties of biopolymers that make up all organisms. This principle underlies the diversity of life on our planet.
Carbohydrates and their structure. Carbohydrates are widespread in the cells of all living organisms. Carbohydrates are organic compounds consisting of carbon, hydrogen and oxygen. In most carbohydrates, hydrogen and oxygen are, as a rule, in the same proportions as in water (hence their name - carbohydrates). The general formula of such carbohydrates is C n (H 2 0) m. An example is one of the most common carbohydrates - glucose, the elemental composition of which is C 6 H 12 0 6 (Fig. 2). Glucose is a simple sugar. Several simple sugar residues combine with each other to form complex sugars. Milk contains milk sugar, which consists of the residues of two simple sugar molecules (disaccharides). Milk sugar is the main source of energy for the young of all mammals.
Thousands of residues of identical sugar molecules combine with each other to form biopolymers - polysaccharides. Living organisms contain many different polysaccharides: in plants it is starch (Fig. 3), in animals it is glycogen, also consisting of thousands of glucose molecules, but even more branched. Starch and glycogen play the role of accumulators of energy necessary for the functioning of body cells. Potatoes, grains of wheat, rye, corn, etc. are very rich in starch.
Functions of carbohydrates. The most important function of carbohydrates is energy. Carbohydrates serve as the main source of energy for organisms that feed on organic matter. In the digestive tract of humans and animals, the polysaccharide starch is broken down by special proteins (enzymes) into monomer units - glucose. Glucose, absorbed from the intestines into the blood, is oxidized in cells to carbon dioxide and water, releasing the energy of chemical bonds, and its excess is stored in liver and muscle cells in the form of glycogen. During periods of intense muscular work or nervous tension (or during fasting), the breakdown of glycogen in the muscles and liver of animals increases. This produces glucose, which is consumed by intensively working muscle and nerve cells.
Thus, biopolymers, polysaccharides, are substances in which the energy of plant and animal organisms used by cells is stored.
In plants, as a result of the polymerization of glucose, not only starch is formed, but also cellulose. Cellulose fibers make up the strong foundation of plant cell walls. Due to its special structure, cellulose is insoluble in water and has high strength. For this reason, cellulose is also used to make fabrics. After all, cotton is almost pure cellulose. In the intestines of humans and most animals there are no enzymes capable of breaking down the bonds between the glucose molecules that make up cellulose. In ruminants, cellulose is broken down by enzymes from bacteria that constantly live in a special section of the stomach.
Complex polysaccharides are also known, consisting of two types of simple sugars that regularly alternate in long chains. Such polysaccharides perform structural functions in the supporting tissues of animals. They are part of the intercellular substance of the skin, tendons, and cartilage, giving them strength and elasticity. Thus, an important function of carbohydrate biopolymers is structural function.
There are polymers of sugars that are part of cell membranes; they ensure the interaction of cells of the same type and recognition of each other by cells. If separated liver cells are mixed with kidney cells, they will independently separate into two groups due to the interaction of cells of the same type: kidney cells will unite into one group, and liver cells into another. Loss of the ability to recognize each other is characteristic of malignant tumor cells. Elucidating the mechanisms of cell recognition and interaction may be important, in particular for the development of cancer treatments.
Lipids. Lipids vary in structure. All of them, however, have one common property: they are all non-polar. Therefore, they dissolve in such non-polar liquids as chloroform and ether, but are practically insoluble in water. Lipids include fats and fat-like substances. In the cell, the oxidation of fats produces a large amount of energy, which is spent on various processes. This is the energy function of fats.
Fats can accumulate in cells and serve as a reserve nutrient. In some animals (for example, whales, pinnipeds), a thick layer of subcutaneous fat is deposited under the skin, which, due to low thermal conductivity, protects them from hypothermia, i.e., performs a protective function.
Some lipids are hormones and take part in the regulation of physiological functions of the body. Lipids containing a phosphoric acid residue (phospholipids) serve as the most important component of cell membranes, i.e. they perform a structural function.
