Presentation Carbohydrates. Lipids presentation for a biology lesson (grade 9) on the topic
Structure, examples and functions of carbohydrates
Carbohydrates- organic compounds, the composition of which in most cases is expressed by the general formula C n(H2O) m (n And m≥ 4). Carbohydrates are divided into monosaccharides, oligosaccharides and polysaccharides.
Monosaccharides- simple carbohydrates, depending on the number of carbon atoms, are divided into trioses (3), tetroses (4), pentoses (5), hexoses (6) and heptoses (7 atoms). The most common are pentoses and hexoses. Properties of monosaccharides- easily dissolves in water, crystallizes, has a sweet taste, and can be presented in the form of α- or β-isomers.
Ribose and deoxyribose belong to the group of pentoses, are part of RNA and DNA nucleotides, ribonucleoside triphosphates and deoxyribonucleoside triphosphates, etc. Deoxyribose (C 5 H 10 O 4) differs from ribose (C 5 H 10 O 5) in that at the second carbon atom it has a hydrogen atom, rather than a hydroxyl group like ribose.
Glucose, or grape sugar(C 6 H 12 O 6), belongs to the group of hexoses, can exist in the form of α-glucose or β-glucose. The difference between these spatial isomers is that at the first carbon atom of α-glucose the hydroxyl group is located under the plane of the ring, while for β-glucose it is above the plane.
Glucose is:
- one of the most common monosaccharides,
- the most important source of energy for all types of work occurring in the cell (this energy is released during the oxidation of glucose during respiration),
- monomer of many oligosaccharides and polysaccharides,
- an essential component of blood.
Fructose, or fruit sugar, belongs to the group of hexoses, sweeter than glucose, found in free form in honey (more than 50%) and fruits. It is a monomer of many oligosaccharides and polysaccharides.
Oligosaccharides- carbohydrates formed as a result of a condensation reaction between several (from two to ten) molecules of monosaccharides. Depending on the number of monosaccharide residues, disaccharides, trisaccharides, etc. are distinguished. Disaccharides are the most common. Properties of oligosaccharides- dissolve in water, crystallize, the sweet taste decreases as the number of monosaccharide residues increases. The bond formed between two monosaccharides is called glycosidic.
Sucrose, or cane, or beet sugar, is a disaccharide consisting of glucose and fructose residues. Contained in plant tissues. Is a food product (common name - sugar). Industrially, sucrose is produced from sugar cane (stems contain 10–18%) or sugar beets (root vegetables contain up to 20% sucrose).
Maltose, or malt sugar, is a disaccharide consisting of two glucose residues. Present in germinating cereal seeds.
Lactose, or milk sugar, is a disaccharide consisting of glucose and galactose residues. Present in the milk of all mammals (2–8.5%).
Polysaccharides- these are carbohydrates formed as a result of the polycondensation reaction of many (several dozen or more) monosaccharide molecules. Properties of polysaccharides- do not dissolve or dissolve poorly in water, do not form clearly formed crystals, and do not have a sweet taste.
Starch(C 6 H 10 O 5) n- a polymer whose monomer is α-glucose. Starch polymer chains contain branched (amylopectin, 1,6-glycosidic linkages) and unbranched (amylose, 1,4-glycosidic linkages) regions. Starch is the main reserve carbohydrate of plants, is one of the products of photosynthesis, and accumulates in seeds, tubers, rhizomes, and bulbs. The starch content in rice grains is up to 86%, wheat - up to 75%, corn - up to 72%, in potato tubers - up to 25%. Starch is the main carbohydrate human food (digestive enzyme - amylase).
Glycogen(C 6 H 10 O 5) n- a polymer whose monomer is also α-glucose. The polymer chains of glycogen resemble the amylopectin regions of starch, but unlike them they branch even more. Glycogen is the main reserve carbohydrate of animals, in particular humans. Accumulates in the liver (content up to 20%) and muscles (up to 4%), and is a source of glucose.
(C 6 H 10 O 5) n- a polymer whose monomer is β-glucose. Cellulose polymer chains do not branch (β-1,4-glycosidic bonds). The main structural polysaccharide of plant cell walls. The cellulose content in wood is up to 50%, in cotton seed fibers - up to 98%. Cellulose is not broken down by human digestive juices, because it lacks the enzyme cellulase, which breaks bonds between β-glucoses.
Inulin- a polymer whose monomer is fructose. Reserve carbohydrate of plants of the Asteraceae family.
Glycolipids- complex substances formed as a result of the combination of carbohydrates and lipids.
Glycoproteins- complex substances formed as a result of the combination of carbohydrates and proteins.
Functions of carbohydrates
| Function | Examples and explanations |
|---|---|
| Energy | The main source of energy for all types of work occurring in cells. When 1 g of carbohydrates is broken down, 17.6 kJ is released. |
| Structural | The cell wall of plants is made of cellulose, the cell wall of bacteria is made of murein, the cell wall of fungi and the integument of arthropods is made of chitin. |
| Storage | The reserve carbohydrate in animals and fungi is glycogen, in plants it is starch and inulin. |
| Protective | Mucus protects the intestines and bronchi from mechanical damage. Heparin prevents blood clotting in animals and humans. |
Structure and functions of lipids
Lipids do not have a single chemical characteristic. In most benefits, giving determination of lipids, they say that this is a collective group of water-insoluble organic compounds that can be extracted from the cell with organic solvents - ether, chloroform and benzene. Lipids can be divided into simple and complex.
Simple lipids Most are represented by esters of higher fatty acids and trihydric alcohol glycerol - triglycerides. Fatty acid have: 1) a group that is the same for all acids - a carboxyl group (–COOH) and 2) a radical by which they differ from each other. The radical is a chain of varying numbers (from 14 to 22) of –CH 2 – groups. Sometimes a fatty acid radical contains one or more double bonds (–CH=CH–), such fatty acid is called unsaturated. If a fatty acid has no double bonds, it is called rich. When a triglyceride is formed, each of the three hydroxyl groups of glycerol undergoes a condensation reaction with a fatty acid to form three ester bonds.
If triglycerides predominate saturated fatty acids, then at 20°C they are solid; they are called fats, they are characteristic of animal cells. If triglycerides predominate unsaturated fatty acids, then at 20 °C they are liquid; they are called oils, they are characteristic of plant cells.
1 - triglyceride; 2 - ester bond; 3 - unsaturated fatty acid; 4 - hydrophilic head; 5 - hydrophobic tail.
The density of triglycerides is lower than that of water, so they float in water and are located on its surface.
Simple lipids also include waxes- esters of higher fatty acids and high molecular weight alcohols (usually with an even number of carbon atoms).
Complex lipids. These include phospholipids, glycolipids, lipoproteins, etc.
Phospholipids- triglycerides in which one fatty acid residue is replaced by a phosphoric acid residue. Take part in the formation of cell membranes.
Glycolipids- see above.
Lipoproteins- complex substances formed as a result of the combination of lipids and proteins.
Lipoids- fat-like substances. These include carotenoids (photosynthetic pigments), steroid hormones (sex hormones, mineralocorticoids, glucocorticoids), gibberellins (plant growth substances), fat-soluble vitamins (A, D, E, K), cholesterol, camphor, etc.
Functions of lipids
| Function | Examples and explanations |
|---|---|
| Energy | The main function of triglycerides. When 1 g of lipids is broken down, 38.9 kJ is released. |
| Structural | Phospholipids, glycolipids and lipoproteins take part in the formation of cell membranes. |
| Storage | Fats and oils are reserve nutrients in animals and plants. Important for animals that hibernate during the cold season or make long treks through areas where there are no food sources. Plant seed oils are necessary to provide energy to the seedling. |
| Protective | Layers of fat and fat capsules provide cushioning for internal organs. Layers of wax are used as a water-repellent coating on plants and animals. |
| Thermal insulation | Subcutaneous fatty tissue prevents the outflow of heat into the surrounding space. Important for aquatic mammals or mammals living in cold climates. |
| Regulatory | Gibberellins regulate plant growth. The sex hormone testosterone is responsible for the development of male secondary sexual characteristics. The sex hormone estrogen is responsible for the development of female secondary sexual characteristics and regulates the menstrual cycle. Mineralocorticoids (aldosterone, etc.) control water-salt metabolism. Glucocorticoids (cortisol, etc.) take part in the regulation of carbohydrate and protein metabolism. |
| Metabolic water source | When 1 kg of fat is oxidized, 1.1 kg of water is released. Important for desert inhabitants. |
| Catalytic | Fat-soluble vitamins A, D, E, K are cofactors for enzymes, i.e. These vitamins themselves do not have catalytic activity, but without them enzymes cannot perform their functions. |
Characteristics of carbohydrates.
In addition to inorganic substances, the cell also includes organic substances: proteins, carbohydrates, lipids, nucleic acids and low molecular weight organic substances.
Proteins 10-20% Water 75-85%
Fats 1-5% Inorganic substances 1.0-1.5%
Carbohydrates 0.2-2.0%
Nucleic acids 1-2%
Low molecular weight organic substances - 0.1-0.5%
Organic substances belong to the group of polymers. There are regular polymers and irregular polymers. An important place among them is occupied by carbohydrates, compounds that contain carbon, oxygen and hydrogen atoms. Their general formula is C m (H 2 O) n, they are divided into simple and complex carbohydrates.
Simple carbohydrates are called monosaccharides. Depending on the number of carbon atoms in the molecule, monosaccharides are distinguished: trioses (3C), tetroses (4C), pentoses (5C), hexoses (6C), heptoses (7C). In nature, pentoses and hexoses are the most widespread. The most important of the pentoses are deoxyribose and ribose, which are part of DNA, RNA and ATP; of the hexoses, the most common are glucose, fructose and galactose (general formula C 6 H 12 O 6).
Monosaccharides can be presented in the form of a- and b-isomers. The hydroxyl group at the first carbon atom can be located both below the ring plane (a-isomer) and above it (b-isomer). Starch molecules consist of a-glucose residues, cellulose - of b-glucose residues.
Deoxyribose (C 5 H 10 O 4) differs from ribose (C 5 H 10 O 5) in that at the second carbon atom it has a hydrogen atom, and not a hydroxyl group like ribose.
Complex carbohydrates are those whose molecules break down during hydrolysis to form simple carbohydrates. Complex carbohydrates include oligosaccharides and polysaccharides.
Oligosaccharides are complex carbohydrates containing from 2 to 10 monosaccharide residues. Depending on the number of monosaccharide residues included in the oligosaccharide molecules, disaccharides, trisaccharides, etc. are distinguished. The most widespread in nature are disaccharides, the molecules of which are formed by two monosaccharide residues - maltose, consisting of two a-glucose residues, milk sugar - lactose and beet (or cane) sugar. They are found in nature in free form or as part of polysaccharides.
Polysaccharides are formed as a result of polycondensation reactions.
The most important polysaccharides are starch, glycogen, cellulose, chitin, murein. Starch is the main reserve carbohydrate in plants, glycogen in animals and humans. Cellulose is the main structural carbohydrate of plant cell walls; it is insoluble in water and is a linear polymer of b-glucose.The properties of monosaccharides and oligosaccharides include their solubility in water and sweet taste. As the number of monomer units increases, solubility decreases and the sweet taste disappears; polysaccharides are insoluble in water.
Functions. The most important function of carbohydrates is energy , carbohydrates are the main sources of energy in the animal body. When 1 g of carbohydrate is broken down, 17.6 kJ of metabolic water and CO 2 are released.
Storage the function is expressed in the accumulation of starch by plant cells and glycogen by animal cells, which play the role of sources of glucose, easily releasing it as needed.
Structural function. Carbohydrates are part of cell membranes and cell walls (cellulose is part of the cell wall of plants, the shell of arthropods is formed from chitin, various oligo- and polysaccharides form the cell wall of bacteria).
Combining with lipids and proteins, they form glycolipids And glycoproteins .
Ribose and deoxyribose are part of nucleotide monomers .
Protective function. The mucus secreted by various glands is rich in carbohydrates and their derivatives (for example, glycoproteins). They protect the esophagus, intestines, stomach, bronchi from mechanical damage, and prevent bacteria and viruses from entering the body. Heparin prevents blood clotting in animals and humans.
Characteristics of lipids.
Lipids are a group of organic compounds that do not have a single chemical characteristic. What they have in common is that they are all insoluble in water, but highly soluble in organic solvents (ether, chloroform, gasoline). Contained in all cells of animals and plants. The lipid content in cells is 5-15% of dry weight, but in adipose tissue it can sometimes reach 90%.
Depending on the structural features of the molecules, they are distinguished: simple and complex lipids. Simple lipids include fats. They are part of the human body, animals, plants, microbes, and some viruses. The fat content in biological objects, tissues and organs can reach 90%.
Fats (triglycerides)- these are esters of higher fatty acids and trihydric alcohol - glycerol.
These are the most common lipids in nature. More than 500 fatty acids have been found in triglycerides, the molecules of which have a similar structure. Fatty acids have the same grouping for all acids - a carboxyl group (–COOH) and a radical by which they differ from each other. The carboxyl group forms the fatty acid head group. It is polar, therefore hydrophilic. The radical is a hydrocarbon tail that differs in different fatty acids in the number of –CH 2 groups. It is non-polar and therefore hydrophobic. When a triglyceride molecule is formed, each of the three hydroxyl (-OH) groups of glycerol undergoes a condensation reaction with a fatty acid, forming three ester bonds, so the resulting compound is called an ester. Physical properties depend on the composition of their molecules. If saturated fatty acids predominate in triglycerides, then they are solid (fats), if unsaturated, they are liquid (oils). The density of fats is lower than that of water, so in water they float and are on the surface.Waxes- a group of simple lipids, which are esters of higher fatty acids and higher high molecular weight alcohols.
Phospholipids- esters of polyhydric alcohols with higher fatty acids containing a phosphoric acid residue. As a rule, a phospholipid molecule contains two higher fatty acid residues and one phosphoric acid residue. Present in all cells of living beings, participating mainly in the formation of cell membranes.
Glycolipids- these are substances formed as a result of the combination of lipids with carbohydrates. They are localized predominantly on the outer surface of the plasma membrane, where their carbohydrate components are included among other cell surface carbohydrates.
Steroids - cholesterol, widely distributed in animal tissues, estradiol and testosterone - female and male sex hormones, respectively; terpenes - essential oils on which the smell of plants depends; gibberellins - plant growth substances; some pigments (chlorophyll, bilirubin) and vitamins (A, D, E, K).Functions of lipids. The main function of lipids is energy. During the breakdown of 1 g of fats to CO2 and H20, 38.9 kJ is released. Structural - lipids take part in the formation of cell membranes. The membranes contain phospholipids, glycolipids, and lipoproteins. Storage function - fats are a reserve substance in animals and plants. This is especially important for animals that hibernate during the cold season or make long treks through areas where there are no food sources (camels in the desert). The seeds of many plants contain fat necessary to provide energy to the developing plant. Thermoregulatory - they are good thermal insulators due to poor thermal conductivity. Protective-mechanical - protect the body from mechanical influences. The catalytic function is associated with fat-soluble vitamins (A, D, E, K). Vitamins themselves do not have catalytic activity, but they are part of many enzymes, and without them these enzymes cannot perform their functions. Metabolic water source - one of the products of fat oxidation is water. This metabolic water is very important for desert inhabitants. Thus, the fat that fills a camel’s hump serves not only as a reserve source of energy, but also as a source of water (when 1 kg of fat is oxidized, 1.1 kg of water is released). And finally, fat reserves increase the buoyancy of aquatic animals.
Carbohydrates- organic compounds, the composition of which in most cases is expressed by the general formula C n(H2O) m
Monosaccharides - simple carbohydrates, depending on the number of carbon atoms, are divided into trioses (3), tetroses (4), pentoses (5), hexoses (6) and heptoses (7 atoms). The most common are pentoses and hexoses. Properties of monosaccharides- easily dissolves in water, crystallizes, has a sweet taste, and can be presented in the form of α- or β-isomers.
Ribose and deoxyribose belong to the group of pentoses, are part of RNA and DNA nucleotides, ribonucleoside triphosphates and deoxyribonucleoside triphosphates, etc. Deoxyribose (C 5 H 10 O 4) differs from ribose (C 5 H 10 O 5) in that at the second carbon atom it has a hydrogen atom, rather than a hydroxyl group like ribose.
Glucose, or grape sugar(C 6 H 12 O 6), belongs to the group of hexoses, can exist in the form of α-glucose or β-glucose. The difference between these spatial isomers is that at the first carbon atom of α-glucose the hydroxyl group is located under the plane of the ring, while for β-glucose it is above the plane.
Glucose is:
- one of the most common monosaccharides,
- the most important source of energy for all types of work occurring in the cell (this energy is released during the oxidation of glucose during respiration),
- monomer of many oligosaccharides and polysaccharides,
- an essential component of blood.
Fructose, or fruit sugar, belongs to the group of hexoses, sweeter than glucose, found in free form in honey (more than 50%) and fruits. It is a monomer of many oligosaccharides and polysaccharides.
Oligosaccharides - carbohydrates formed as a result of a condensation reaction between several (from two to ten) molecules of monosaccharides. Depending on the number of monosaccharide residues, disaccharides, trisaccharides, etc. are distinguished. Disaccharides are the most common. Properties of oligosaccharides- dissolve in water, crystallize, the sweet taste decreases as the number of monosaccharide residues increases. The bond formed between two monosaccharides is called glycosidic.
Sucrose, or cane, or beet sugar, is a disaccharide consisting of glucose and fructose residues. Contained in plant tissues. Is a food product (common name - sugar). In industry, sucrose is produced from sugar cane (stems contain 10-18%) or sugar beets (root vegetables contain up to 20% sucrose).
Maltose, or malt sugar, is a disaccharide consisting of two glucose residues. Present in germinating cereal seeds.
Lactose, or milk sugar, is a disaccharide consisting of glucose and galactose residues. Present in the milk of all mammals (2-8.5%).
Polysaccharides are carbohydrates formed as a result of the polycondensation reaction of many (several dozen or more) monosaccharide molecules. Properties of polysaccharides— do not dissolve or dissolve poorly in water, do not form clearly formed crystals, and do not have a sweet taste.
Starch(C 6 H 10 O 5) n- a polymer whose monomer is α-glucose. Starch polymer chains contain branched (amylopectin, 1,6-glycosidic linkages) and unbranched (amylose, 1,4-glycosidic linkages) regions. Starch is the main reserve carbohydrate of plants, is one of the products of photosynthesis, and accumulates in seeds, tubers, rhizomes, and bulbs. The starch content in rice grains is up to 86%, wheat - up to 75%, corn - up to 72%, and potato tubers - up to 25%. Starch is the main carbohydrate human food (digestive enzyme - amylase).
Glycogen(C 6 H 10 O 5) n- a polymer whose monomer is also α-glucose. The polymer chains of glycogen resemble the amylopectin regions of starch, but unlike them they branch even more. Glycogen is the main reserve carbohydrate of animals, in particular humans. Accumulates in the liver (content up to 20%) and muscles (up to 4%), and is a source of glucose.
(C 6 H 10 O 5) n- a polymer whose monomer is β-glucose. Cellulose polymer chains do not branch (β-1,4-glycosidic bonds). The main structural polysaccharide of plant cell walls. The cellulose content in wood is up to 50%, in cotton seed fibers - up to 98%. Cellulose is not broken down by human digestive juices, because it lacks the enzyme cellulase, which breaks bonds between β-glucoses.
Inulin- a polymer whose monomer is fructose. Reserve carbohydrate of plants of the Asteraceae family.
Glycolipids- complex substances formed as a result of the combination of carbohydrates and lipids.
Glycoproteins- complex substances formed by combining carbohydrates and proteins.
Functions of carbohydrates
Structure and functions of lipids
Lipids do not have a single chemical characteristic. In most benefits, giving determination of lipids, they say that this is a collective group of water-insoluble organic compounds that can be extracted from the cell with organic solvents - ether, chloroform and benzene. Lipids can be divided into simple and complex.
Simple lipids Most are represented by esters of higher fatty acids and trihydric alcohol glycerol - triglycerides. Fatty acid have: 1) a group that is the same for all acids - a carboxyl group (-COOH) and 2) a radical by which they differ from each other. The radical is a chain of varying numbers (from 14 to 22) of -CH 2 - groups. Sometimes a fatty acid radical contains one or more double bonds (-CH=CH-), such fatty acid is called unsaturated. If a fatty acid has no double bonds, it is called rich. When a triglyceride is formed, each of the three hydroxyl groups of glycerol undergoes a condensation reaction with a fatty acid to form three ester bonds.
If triglycerides predominate saturated fatty acids, then at 20°C they are solid; they are called fats, they are characteristic of animal cells. If triglycerides predominate unsaturated fatty acids, then at 20 °C they are liquid; they are called oils, they are characteristic of plant cells.
1 - triglyceride; 2 - ester bond; 3 - unsaturated fatty acid; 4 — hydrophilic head; 5 - hydrophobic tail.
The density of triglycerides is lower than that of water, so they float in water and are located on its surface.
Simple lipids also include waxes- esters of higher fatty acids and high molecular weight alcohols (usually with an even number of carbon atoms).
Complex lipids. These include phospholipids, glycolipids, lipoproteins, etc.
Phospholipids- triglycerides in which one fatty acid residue is replaced by a phosphoric acid residue. Take part in the formation of cell membranes.
Glycolipids- see above.
Lipoproteins- complex substances formed as a result of the combination of lipids and proteins.
Lipoids- fat-like substances. These include carotenoids (photosynthetic pigments), steroid hormones (sex hormones, mineralocorticoids, glucocorticoids), gibberellins (plant growth substances), fat-soluble vitamins (A, D, E, K), cholesterol, camphor, etc.
Functions of lipids
| Function | Examples and explanations |
|---|---|
| Energy | The main function of triglycerides. When 1 g of lipids is broken down, 38.9 kJ is released. |
| Structural | Phospholipids, glycolipids and lipoproteins take part in the formation of cell membranes. |
| Storage | Fats and oils are reserve nutrients in animals and plants. Important for animals that hibernate during the cold season or make long treks through areas where there are no food sources. Plant seed oils are necessary to provide energy to the seedling. |
| Protective | Layers of fat and fat capsules provide cushioning for internal organs. Layers of wax are used as a water-repellent coating on plants and animals. |
| Thermal insulation | Subcutaneous fatty tissue prevents the outflow of heat into the surrounding space. Important for aquatic mammals or mammals living in cold climates. |
| Regulatory | Gibberellins regulate plant growth. The sex hormone testosterone is responsible for the development of male secondary sexual characteristics. The sex hormone estrogen is responsible for the development of female secondary sexual characteristics and regulates the menstrual cycle. Mineralocorticoids (aldosterone, etc.) control water-salt metabolism. Glucocorticoids (cortisol, etc.) take part in the regulation of carbohydrate and protein metabolism. |
| Metabolic water source | When 1 kg of fat is oxidized, 1.1 kg of water is released. Important for desert inhabitants. |
| Catalytic | Fat-soluble vitamins A, D, E, K are cofactors for enzymes, i.e. These vitamins themselves do not have catalytic activity, but without them enzymes cannot perform their functions. |
Functions of lipids
Information sources
http://www.licey.net/bio/biology/lection2
http://sbio.info/page.php?id=9
http://humbio.ru/humbio/biochem/001dd1b4.htm
DYNAMIC BIOCHEMISTRY
Part 2. METABOLISM AND FUNCTIONS OF LIPIDS
TUTORIAL
FOR INDEPENDENT WORK OF STUDENTS
Reviewer: Associate Professor N.U. Tankibaeva
Approved at the meeting of the department, pr. No. _____ dated _______________2003.
Approved by the manager department _____________________________________________
Approved by the MK of the medical-biological and pharmaceutical faculties
Project No. _____ dated _______________2004
Chairman________________________________________________
GENERAL CHARACTERISTICS OF LIPIDS
In the body they perform the following Features:
1. structural- are part of cell membranes,
2. regulatory- some lipids are vitamins and hormones and are involved in the transmission of nerve impulses,
3. transport- lipoproteins, a complex of fatty acids with albumin,
4. thermoregulatory- take part in the thermal insulation of the body
5. energy- direct sources of energy and substances that are stored for later use in case of energy deficiency.
Lipids are a group of natural hydrophobic substances diverse in structure and function. These include fats - the most advantageous form of storing energy sources; phospholipids - the structural basis of all types of membranes, a necessary element of lipoproteins - transport forms of lipids in the blood; cholesterol is a component of membranes and a precursor in the synthesis of bile acids and steroid hormones. Many lipids and their derivatives: phosphatidylinositol triphosphates, diacylglycerols, polyene fatty acids and a large group of eicosanoids formed from them - have the properties of local hormones and perform regulatory functions. Natural lipids include a number of essential nutritional factors for humans: fat-soluble vitamins and polyene fatty acids.
A common property of all lipids is hydrophobicity. But some lipids (glycolipids, phospholipids, bile acids) are amphiphilic, since they contain hydrophilic and hydrophobic parts.
The biological functions of lipids are determined primarily by the fact that they are sources of energy. This function is performed by fatty acids released after the breakdown of fats.
Unlike carbohydrates, fats make up the body's energy reserve. The advantage of fat as an energy reserve is that fats are more reduced substances compared to carbohydrates (carbohydrate molecules have oxygen at each carbon atom - “–CHOH-” groups; fat has long hydrocarbon radicals, in which “” groups predominate). -CH 2 -“ - they have no oxygen). More hydrogen can be removed from fat, which then passes through the mitochondrial oxidation chain to produce ATP.
Calorie content of carbohydrates and proteins: ~ 4 kcal/gram. Caloric content of fat: ~ 9 kcal/gram.
The advantage of fat as an energy reserve, unlike carbohydrates, is its hydrophobicity - it is not associated with water. This ensures compactness of fat reserves - they are stored in anhydrous form, occupying a small volume.
The body contains 30 times more fat than glycogen (0.3 kg of glycogen and 10 kg of fat). Normally, the fat content in the human body is 6-10 kg. This amount of fat is enough to provide energy to the body for 40 days during complete fasting. Glycogen is enough for about 1 day of fasting.
Glycogen reserves in cells are used up throughout the day, with the exception of approximately two-hour periods after meals. Fats deposited in adipose tissue may not be consumed: with a normal nutritional rhythm, there are always lipoproteins in the blood that supply the organs with fatty acids. In terms of their role in energy metabolism, fats stored in lipoproteins are more similar to glycogen than fats stored in adipose tissue.
An important feature of fats is that their hydrolysis produces two functionally different products - fatty acids and glycerol. Glycerol is used for gluconeogenesis and thereby participates in the supply of glucose to brain cells and other glucose-dependent cells during fasting. Thus, fat storage can be considered a form of glucose storage.
The formation of fat reserves in the body of humans and some animals is considered as an adaptation to irregular nutrition and living in a cold environment. Animals that hibernate for a long time (bears, marmots) and are adapted to living in cold conditions (walruses, seals) have a particularly large reserve of fat. The fetus has virtually no fat and appears only before birth.
The structure and functions of the main lipids are given in Table 1.
Table 1.
The chemical name for fats is acylglycerols, that is, fats. These are esters of glycerol and higher fatty acids. "Acyl-" means "fatty acid residue" (not to be confused with "acetyl-" - acetic acid residue). Depending on the number of acyl radicals, fats are divided into mono-, di- and triglycerides. If the molecule contains 2 fatty acid radicals, then the fat is called DIACYLGLYCEROL. If the molecule contains 1 fatty acid radical, then the fat is called MONOACYLGLYCEROL.
In the human and animal body, TRIACYLGLYCEROLS predominate (contain three fatty acid radicals).
The properties of fat are determined by the composition of fatty acids.
The membranes contain only LIPOIDS (complex lipids): phospholipids (PL), glycolipids (GL) and the steroid cholesterol (CS).
Phospholipids are lipids containing a phosphate residue. Consists of four components:
2) fatty acids;
3) phosphate;
4) polar group (If it is serine, then the glycerophospholipid is called phosphatidylyserine, if it is choline, then the glycerophospholipid is called phosphatidylcholine, if it is ethanolamine, then the glycerophospholipid is called phosphatidylethanolamine, if it is inositol, then the glycerophospholipid is called phosphatidylinositol).
GENERAL FORMULA OF GLYCEROPHOSPHOLIPIDS:
 |
Phospholipids may contain 2 alcohols: glycerol (glycerophospholipids) and sphingosine (sphingophospholipids, sphingomyelins). All components are connected by etheric bonds. In addition to dividing based on the content of a particular polar group, they are divided based on the alcohol they contain:
1. GLYCEROPHOSPHOLIPIDS(GFL) - contain alcohol glycerin.
All of them belong to the L-series. There is an asymmetric carbon atom (indicated by an asterisk in the figure). The polar group can be represented by the amino acid serine (phosphatidylserine), choline (phosphatidylcholine, another name is lecithin), ethanolamine (phosphatidylethanolamine), inositol (phosphatidylinositol), glycerol (polyglycerophosphatides).
In natural phospholipids, R1 and R2 are different. R 1 is a saturated fatty acid, R 2 is an unsaturated fatty acid. However, there are exceptions: the main lipid component of pulmonary surfactant is HPL, in which both R1 and R2 are palmitic acid radicals, and the polar group is choline.
2. SPHINGOPHOSPHOLIPIDS(SFL) - contain the alcohol sphingosine: SPHINGOMYELINS.
Sphingophospholipids vary in structure, but have common features. The sphingophospholipid molecule contains sphingosine, a fatty acid, phosphoric acid and a polar group.
The GENERAL FORMULA of SFL is presented in the figure. 
Sphingosine is a 2-hydroxy unsaturated amino alcohol.
The fatty acid is attached by a peptide bond to the amino group of sphingosine.
Phospholipids are amphiphilic substances. The arrangement of hydrophilic and hydrophobic areas is special. Hydrophilic sites (phosphoric acid residue and polar group) form the “head”, and hydrophobic fatty acid radicals (R 1 and R 2) form the “tails”.
GLYCOLIPIDS.
They consist of sphingosine, a fatty acid and a molecule of some carbohydrate. If we put some carbohydrate in the SFL formula instead of phosphoric acid, we get the GL formula. Glycolipids also have a hydrophilic head and two hydrophobic tails. The general diagram of their structure is shown in the figure:
Glycolipids are classified depending on the structure of the carbohydrate component.
There are 2 groups of glycolipids:
1. CEREBROSIDES. As a carbohydrate component they contain a monosaccharide (glucose, galactose), or a disaccharide, or a neutral small oligosaccharide.
2. GANGLIOSIDES. The carbohydrate component is an oligosaccharide, consisting of different monomers, both monosaccharides themselves and their derivatives. This oligosaccharide is necessarily acidic and contains sialic acid. Due to a certain sequence of monomers, oligosaccharides in the ganglioside composition give the molecule pronounced antigenic properties.
STEROIDS.
Divided into 2 groups.
1. Steri n s (they contain a polycyclic sterane structure).
2. Steri d s (esters of cholesterol and higher fatty acids).
Properties of steroids.
Steri n They contain a hydroxyl group (-OH), so they are slightly hydrophilic, but their molecules are still mostly hydrophobic. These include cholesterol.
Cholesterol is a polycyclic substance. Hydrophobic properties predominate, but there is one OH group.
Steri d s are completely hydrophobic substances.
FATTY ACID
Fatty acids are part of most lipids in the human body. They can be associated with both glycerol (TAG and glycerophospholipids) and the amino alcohol sphingosine, forming a group of sphingolipids. Fatty foods, along with glucose, are the most important sources of energy. (“fuel molecules”).
An acid is called fatty if the number of carbon atoms in its molecule is more than four. Long-chain fatty acids predominate (carbon number 16 or higher). The number of carbon atoms and double bonds is indicated by a double subscript. For example: C18:1 (9-10). In this case, 18 is the number of carbon atoms and 1 is the number of double bonds. The location of double bonds (by carbon atom numbers) is indicated in parentheses.
C16:0 - palmitic,
Carbohydrates— organic compounds with the general formula Cn(H20)m, m > n. The chemical properties of carbohydrates are determined by the hydroxyl groups (—OH) they contain. There are simple (monosaccharides) and complex (oligosaccharides, polysaccharides) carbohydrates. Monosaccharides consist of one carbohydrate molecule (glucose, fructose, ribose, deoxyribose). Depending on the number of carbon atoms, they are distinguished: trioses - three atoms, tetroses - 4 atoms, pentoses - 5 atoms, hexoses - six atoms, etc. Properties of monosaccharides: low molecular weight, sweet taste, soluble in water, capable of crystallization.Oligosaccharides- sugar-like complex carbohydrates containing from 2 to 10 monosaccharide residues. Depending on their quantity, di-, tri-, tetrasaccharides, etc. are distinguished. Disaccharides are formed when two monosaccharides are joined by a glycosidic bond (glucose + glucose = maltose, glucose + galactose = lactose, glucose + fructose = sucrose). Typically, a glycosidic bond is formed between the 1st and 4th carbon atoms of adjacent monosaccharide units.
Polysaccharides (starch and cellulose (in plants), glycogen (in animals)). The monomer of these polysaccharides is glucose. They can be linear, unbranched or branched.
Meaning of carbohydrates:
. source of energy in the cell (1 g of carbohydrate - 17.6 kJ (4.2 kcal) energy);
. cell reserve (starch, glycogen);
. construction function (murein in prokaryotes; fiber in plants and fungi; ribose and deoxyribose in nucleic acids);
. receptor function (glycolipids);
. protective function (heparin slows down blood clotting).
Lipids- fat-like, water-insoluble substances. According to their chemical composition, lipids are esters of higher fatty acids and the trihydric alcohol glycerol. Fatty acids can be either saturated (do not contain double bonds - stearic and palmitic) or unsaturated (have double bonds between carbon atoms - oleic). Depending on the structural features of the molecules, simple (triglycerides, waxes) and complex (phospholipids, glycolipids, lipoids) lipids are distinguished. Lipid value:
. are part of membranes (phospholipids, glycolipids, lipoproteins);
. transport (lipoproteins);
. receptors, mediators (glycolipids in the glycocalyx);
. source of energy (when 1 g of fat is broken down, 38.9 kJ of energy is released);
. storage function;
. protection (water-repellent coating - plant wax);
. thermostat and heat insulator, shock absorber (brown fat);
. regulation of cell and body activity (hormones - estrogen, progesterone, testosterone, corticosterone, cortisone, cholesterol), as part of gibberellins (growth substances in plants);
. source of metabolic water.
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