LIPIDS - this is a heterogeneous group of natural compounds, completely or almost completely insoluble in water, but soluble in organic solvents and in each other, yielding high molecular weight fatty acids upon hydrolysis.
In a living organism, lipids perform various functions.
Biological functions of lipids:
1) Structural
Structural lipids form complex complexes with proteins and carbohydrates, from which the membranes of cells and cellular structures are built, and participate in a variety of processes occurring in the cell.
2) Spare (energy)
Reserve lipids (mainly fats) are the body's energy reserve and participate in metabolic processes. In plants they accumulate mainly in fruits and seeds, in animals and fish - in subcutaneous fatty tissues and tissues surrounding internal organs, as well as liver, brain and nervous tissues. Their content depends on many factors (type, age, nutrition, etc.) and in some cases accounts for 95-97% of all secreted lipids.
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 average person's supply of pure triacylglycerols is approximately 13 kg. These reserves could be enough for 40 days of fasting in moderate conditions. physical activity. For comparison: total reserves glycogen in the body - approximately 400 g; when fasting, this amount is not enough even for one day.
3) Protective
Subcutaneous adipose tissue protects animals from cooling, and internal organs from mechanical damage.
The formation of fat reserves in the body of humans and some animals is considered 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.
A special group in terms of their functions in a living organism are the protective lipids of plants - waxes and their derivatives, covering the surface of leaves, seeds and fruits.
4) An important component of food raw materials
Lipids are an important component food, largely determining its nutritional value and taste. The role of lipids in various food technology processes is extremely important. Spoilage of grain and its processed products during storage (rancidity) is primarily associated with changes in its lipid complex. Lipids isolated from a number of plants and animals are the main raw materials for obtaining the most important food and technical products (vegetable oil, animal fats, including butter, margarine, glycerin, fatty acids and etc.).
2 Classification of lipids
There is no generally accepted classification of lipids.
It is most appropriate to classify lipids depending on their chemical nature, biological functions, and also in relation to certain reagents, for example, alkalis.
Based on their chemical composition, lipids are usually divided into two groups: simple and complex.
Simple lipids – esters of fatty acids and alcohols. These include fats , waxes And steroids .
Fats – esters of glycerol and higher fatty acids.
Waxes – esters of higher alcohols of the aliphatic series (with a long carbohydrate chain of 16-30 C atoms) and higher fatty acids.
Steroids – esters of polycyclic alcohols and higher fatty acids.
Complex lipids – in addition to fatty acids and alcohols, they contain other components of various chemical natures. These include phospholipids and glycolipids .
Phospholipids - these are complex lipids in which one of the alcohol groups is associated not with FA, but with phosphoric acid (phosphoric acid can be connected to an additional compound). Depending on which alcohol is included in the phospholipids, they are divided into glycerophospholipids (contain the alcohol glycerol) and sphingophospholipids (contain the alcohol sphingosine).
Glycolipids – these are complex lipids in which one of the alcohol groups is associated not with FA, but with a carbohydrate component. Depending on which carbohydrate component is part of the glycolipids, they are divided into cerebrosides (they contain a monosaccharide, disaccharide or a small neutral homooligosaccharide as a carbohydrate component) and gangliosides (they contain an acidic heterooligosaccharide as a carbohydrate component).
Sometimes into an independent group of lipids ( minor lipids ) secrete fat-soluble pigments, sterols, and fat-soluble vitamins. Some of these compounds can be classified as simple (neutral) lipids, others - complex.
According to another classification, lipids, depending on their relationship to alkalis, are divided into two large groups: saponifiable and unsaponifiable. The group of saponified lipids includes simple and complex lipids, which, when interacting with alkalis, hydrolyze to form salts of high molecular weight acids, called “soaps”. The group of unsaponifiable lipids includes compounds that are not subject to alkaline hydrolysis (sterols, fat-soluble vitamins, ethers, etc.).
According to their functions in a living organism, lipids are divided into structural, storage and protective.
Structural lipids are mainly phospholipids.
Storage lipids are mainly fats.
Protective lipids of plants - waxes and their derivatives, covering the surface of leaves, seeds and fruits, animals - fats.
FATS
The chemical name of fats is acylglycerols. These are esters of glycerol and higher fatty acids. "Acyl" means "fatty acid residue".
Depending on the number of acyl radicals, fats are divided into mono-, di- and triglycerides. If the molecule contains 1 fatty acid radical, then the fat is called MONOACYLGLYCEROL. If the molecule contains 2 fatty acid radicals, then the fat is called DIACYLGLYCEROL. In the human and animal body, TRIACYLGLYCEROLS predominate (contain three fatty acid radicals).
The three hydroxyls of glycerol can be esterified either with only one acid, such as palmitic or oleic, or with two or three different acids:
Natural fats contain mainly mixed triglycerides, including residues of various acids.
Since the alcohol in all natural fats is the same - glycerol, the differences observed between fats are due solely to the composition of fatty acids.
More than four hundred were found in fats carboxylic acids of various structures. However, most of them are present only in small quantities.
The acids contained in natural fats are monocarboxylic acids, built from unbranched carbon chains containing an even number of carbon atoms. Acids containing an odd number of carbon atoms, having a branched carbon chain, or containing cyclic moieties are present in small quantities. The exceptions are isovaleric acid and a number of cyclic acids found in some very rare fats.
The most common acids in fats contain 12 to 18 carbon atoms and are often called fatty acids. Many fats contain small amounts of low molecular weight acids (C 2 -C 10). Acids with more than 24 carbon atoms are present in waxes.
The glycerides of the most common fats contain significant quantities of unsaturated acids containing 1-3 double bonds: oleic, linoleic and linolenic. Arachidonic acid containing four double bonds is present in animal fats; acids with five, six or more double bonds are found in fats of fish and marine animals. Most unsaturated acids of lipids have a cis configuration, their double bonds are isolated or separated by a methylene (-CH 2 -) group.
Of all the unsaturated acids contained in natural fats, oleic acid is the most common. In many fats, oleic acid makes up more than half of the total mass of acids, and only a few fats contain less than 10%. Two other unsaturated acids - linoleic and linolenic acid - are also very widespread, although they are present in much smaller quantities than oleic acid. Linoleic and linolenic acids are found in noticeable quantities in vegetable oils; For animal organisms they are essential acids.
Of the saturated acids, palmitic acid is almost as widespread as oleic acid. It is present in all fats, with some containing 15-50% of the total acid content. Stearic and myristic acids are widely used. Stearic acid is found in large quantities (25% or more) only in the storage fats of some mammals (for example, in sheep fat) and in the fats of some tropical plants, such as cocoa butter.
It is advisable to divide the acids contained in fats into two categories: major and minor acids. The main acids of fat are acids whose content in fat exceeds 10%.
Physical properties of fats
As a rule, fats do not withstand distillation and decompose even if they are distilled under reduced pressure.
The melting point, and therefore the consistency of fats, depends on the structure of the acids that make up them. Solid fats, i.e. fats that melt at a relatively high temperature, consist predominantly of glycerides of saturated acids (stearic, palmitic), and oils that melt at a lower temperature and are thick liquids contain significant amounts of glycerides of unsaturated acids (oleic , linoleic, linolenic).
Since natural fats are complex mixtures of mixed glycerides, they do not melt at a certain temperature, but in a certain temperature range, and they are first softened. To characterize fats, it is usually used solidification temperature, which does not coincide with the melting point - it is slightly lower. Some natural fats are solids; others are liquids (oils). The solidification temperature varies widely: -27 °C for linseed oil, -18 °C for sunflower oil, 19-24 °C for cow lard and 30-38 °C for beef lard.
The solidification temperature of fat is determined by the nature of its constituent acids: the higher the content of saturated acids, the higher it is.
Fats are soluble in ether, polyhalogen derivatives, carbon disulfide, aromatic hydrocarbons (benzene, toluene) and gasoline. Solid fats are poorly soluble in petroleum ether; insoluble in cold alcohol. Fats are insoluble in water, but they can form emulsions that are stabilized in the presence of surfactants (emulsifiers) such as proteins, soaps and some sulfonic acids, mainly in a slightly alkaline environment. Milk is a natural fat emulsion stabilized by proteins.
Chemical properties of fats
Fats undergo all chemical reactions characteristic of esters, but their chemical behavior has a number of features associated with the structure of fatty acids and glycerol.
Among the chemical reactions involving fats, several types of transformations are distinguished.
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The site provides background information for informational purposes only. Diagnosis and treatment of diseases must be carried out under the supervision of a specialist. All drugs have contraindications. Consultation with a specialist is required!
What kind of substances are lipids?
Lipids represent one of the groups of organic compounds having great value for living organisms. According to their chemical structure, all lipids are divided into simple and complex. Simple lipids are made up of alcohol and bile acids, while complex lipids contain other atoms or compounds. In general, lipids are of great importance to humans. These substances are included in a significant part of food products, are used in medicine and pharmacy, and play an important role in many industries. In a living organism, lipids in one form or another are part of all cells. From a nutritional point of view, it is a very important source of energy.
What is the difference between lipids and fats?
Basically, the term "lipids" comes from a Greek root meaning "fat", but there are still some differences between these definitions. Lipids are a larger group of substances, while fats refer to only certain types of lipids. A synonym for “fats” are “triglycerides,” which are obtained from a combination of glycerol alcohol and carboxylic acids. Both lipids in general and triglycerides in particular play a significant role in biological processes.Lipids in the human body
Lipids are part of almost all tissues of the body. Their molecules are present in any living cell, and without these substances life is simply impossible. There are many different lipids found in the human body. Each type or class of these compounds has its own functions. Many biological processes depend on the normal supply and formation of lipids. From a biochemical point of view, lipids take part in the following important processes:
- energy production by the body;
- cell division;
- transmission of nerve impulses;
- formation of blood components, hormones and other important substances;
- protection and fixation of some internal organs;
- cell division, respiration, etc.
Biological role of lipids in a living cell
Lipid molecules perform great amount functions not only on the scale of the entire organism, but also in each living cell individually. In essence, a cell is a structural unit of a living organism. It is where assimilation and synthesis occurs ( education) certain substances. Some of these substances go to maintaining the life of the cell itself, some to cell division, and some to the needs of other cells and tissues.In a living organism, lipids perform the following functions:
- energy;
- reserve;
- structural;
- transport;
- enzymatic;
- storing;
- signal;
- regulatory
Energy function
The energy function of lipids is reduced to their breakdown in the body, during which a large amount of energy is released. Living cells need this energy to maintain various processes ( respiration, growth, division, synthesis of new substances). Lipids enter the cell with blood flow and are deposited inside ( in the cytoplasm) in the form of small drops of fat. If necessary, these molecules are broken down and the cell receives energy.Reserve ( storing) function
The reserve function is closely related to the energy function. In the form of fats inside cells, energy can be stored “in reserve” and released as needed. Special cells – adipocytes – are responsible for the accumulation of fats. Most of their volume is occupied by a large drop of fat. It is adipocytes that make up adipose tissue in the body. The largest reserves of adipose tissue are located in the subcutaneous fat, the greater and lesser omentum ( V abdominal cavity ). During prolonged fasting, adipose tissue gradually breaks down, as lipid reserves are used to obtain energy.Also, adipose tissue deposited in subcutaneous fat provides thermal insulation. Tissues rich in lipids are generally poorer conductors of heat. This allows the body to maintain constant temperature body and not cool down or overheat so quickly in different conditions external environment.
Structural and barrier functions ( membrane lipids)
Lipids play a huge role in the structure of living cells. In the human body, these substances form a special double layer that forms the cell wall. Thereby living cell can perform its functions and regulate metabolism with the external environment. Lipids that form the cell membrane also help maintain the shape of the cell.Why do lipid monomers form a double layer ( bilayer)?
Monomers are called chemical substances (V in this case– molecules), which are capable of combining to form more complex compounds. The cell wall consists of a double layer ( bilayer) lipids. Each molecule that forms this wall has two parts - hydrophobic ( not in contact with water) and hydrophilic ( in contact with water). The double layer is obtained due to the fact that the lipid molecules are deployed with hydrophilic parts inside and outside the cell. The hydrophobic parts practically touch, as they are located between the two layers. Other molecules may also be located in the depth of the lipid bilayer ( proteins, carbohydrates, complex molecular structures), which regulate the passage of substances through the cell wall.Transport function
The transport function of lipids is of secondary importance in the body. Only some connections do this. For example, lipoproteins, consisting of lipids and proteins, transport certain substances in the blood from one organ to another. However, this function is rarely isolated, without considering it to be the main one for these substances.Enzymatic function
In principle, lipids are not part of the enzymes involved in the breakdown of other substances. However, without lipids, organ cells will not be able to synthesize enzymes, the end product of vital activity. In addition, some lipids play a significant role in the absorption of dietary fats. Bile contains significant amounts of phospholipids and cholesterol. They neutralize excess pancreatic enzymes and prevent them from damaging intestinal cells. Dissolution also occurs in bile ( emulsification) exogenous lipids coming from food. Thus, lipids play a huge role in digestion and help in the work of other enzymes, although they are not enzymes themselves.Signal function
Some complex lipids perform a signaling function in the body. It consists of maintaining various processes. For example, glycolipids in nerve cells take part in the transmission of nerve impulses from one nerve cell to another. Besides, great importance have signals within the cell itself. She needs to “recognize” substances entering the blood in order to transport them inside.Regulatory function
The regulatory function of lipids in the body is secondary. The lipids themselves in the blood have little effect on the course of various processes. However, they are part of other substances that are of great importance in the regulation of these processes. First of all, these are steroid hormones ( adrenal hormones and sex hormones). They play an important role in metabolism, growth and development of the body, reproductive function, affect work immune system. Lipids are also part of prostaglandins. These substances are produced during inflammatory processes and affect some processes in nervous system (for example, pain perception).Thus, lipids themselves do not perform a regulatory function, but their deficiency can affect many processes in the body.
Biochemistry of lipids and their relationship with other substances ( proteins, carbohydrates, ATP, nucleic acids, amino acids, steroids)
Lipid metabolism is closely related to the metabolism of other substances in the body. First of all, this connection can be traced in human nutrition. Any food consists of proteins, carbohydrates and lipids, which must enter the body in certain proportions. In this case, a person will receive both enough energy and enough structural elements. Otherwise ( for example, with a lack of lipids) proteins and carbohydrates will be broken down to produce energy.Also, lipids are, to one degree or another, associated with the metabolism of the following substances:
- Adenosine triphosphoric acid ( ATP). ATP is a unique unit of energy inside a cell. When lipids are broken down, part of the energy goes into the production of ATP molecules, and these molecules take part in all intracellular processes ( transport of substances, cell division, neutralization of toxins, etc.).
- Nucleic acids. Nucleic acids are structural elements DNA is found in the nuclei of living cells. The energy generated during the breakdown of fats is partially used for cell division. During division, new DNA chains are formed from nucleic acids.
- Amino acids. Amino acids are structural components of proteins. In combination with lipids, they form complex complexes, lipoproteins, responsible for the transport of substances in the body.
- Steroids. Steroids are a type of hormone that contains significant amounts of lipids. If lipids from food are poorly absorbed, the patient may experience problems with the endocrine system.
Digestion and absorption of lipids ( metabolism, metabolism)
Digestion and absorption of lipids is the first stage in the metabolism of these substances. The main part of lipids enters the body with food. IN oral cavity food is crushed and mixed with saliva. Next, the lump enters the stomach, where the chemical bonds are partially destroyed by hydrochloric acid. Also, some chemical bonds in lipids are destroyed by the enzyme lipase contained in saliva.Lipids are insoluble in water, so they are not immediately broken down by enzymes in the duodenum. First, the so-called emulsification of fats occurs. After this, the chemical bonds are broken down by lipase coming from the pancreas. In principle, each type of lipid now has its own enzyme responsible for the breakdown and absorption of this substance. For example, phospholipase breaks down phospholipids, cholesterol esterase breaks down cholesterol compounds, etc. All these enzymes are contained in varying quantities in pancreatic juice.
Cleaved lipid fragments are individually absorbed by cells small intestine. In general, the digestion of fats is a very difficult process, which is regulated by many hormones and hormone-like substances.
What is lipid emulsification?
Emulsification is the incomplete dissolution of fatty substances in water. In a bolus of food entering duodenum, fats are contained in the form of large drops. This prevents them from interacting with enzymes. During the emulsification process, large fat droplets are “crushed” into smaller droplets. As a result, the contact area between fat droplets and surrounding water-soluble substances increases, and lipid breakdown becomes possible.The process of emulsifying lipids into digestive system takes place in several stages:
- At the first stage, the liver produces bile, which will emulsify fats. It contains salts of cholesterol and phospholipids, which interact with lipids and contribute to their “crushing” into small droplets.
- Bile secreted from the liver accumulates in the gallbladder. Here it is concentrated and released as needed.
- When consumed fatty foods, a signal is sent to the smooth muscles of the gallbladder to contract. As a result, a portion of bile is released through the bile ducts into the duodenum.
- In the duodenum, fats are actually emulsified and interact with pancreatic enzymes. Contractions in the walls of the small intestine facilitate this process by “mixing” the contents.
Enzymes for lipid breakdown
To digest each substance, the body has its own enzymes. Their task is to break chemical bonds between molecules ( or between atoms in molecules) so that nutrients can be properly absorbed by the body. Different enzymes are responsible for breaking down different lipids. Most of them are contained in the juice secreted by the pancreas.The following groups of enzymes are responsible for the breakdown of lipids:
- lipases;
- phospholipases;
- cholesterol esterase, etc.
What vitamins and hormones are involved in the regulation of lipid levels?
The levels of most lipids in human blood are relatively constant. It can fluctuate within certain limits. This depends on the biological processes occurring in the body itself, and on a number of external factors. Regulating blood lipid levels is complex biological process, in which many take part various organs and substances.The following substances play the greatest role in the absorption and maintenance of constant lipid levels:
- Enzymes. A number of pancreatic enzymes take part in the breakdown of lipids entering the body with food. With a lack of these enzymes, the level of lipids in the blood may decrease, since these substances simply will not be absorbed in the intestines.
- Bile acids and their salts. Bile contains bile acids and a number of their compounds, which contribute to the emulsification of lipids. Without these substances, normal absorption of lipids is also impossible.
- Vitamins. Vitamins have a complex strengthening effect on the body and also directly or indirectly affect lipid metabolism. For example, with a lack of vitamin A, cell regeneration in the mucous membranes deteriorates, and the digestion of substances in the intestines also slows down.
- Intracellular enzymes. The intestinal epithelial cells contain enzymes that, after absorption of fatty acids, convert them into transport forms and send them into the bloodstream.
- Hormones. A number of hormones affect metabolism in general. For example, high level Insulin can greatly affect blood lipid levels. That is why some standards have been revised for patients with diabetes. Thyroid hormones, glucocorticoid hormones, or norepinephrine can stimulate the breakdown of fat tissue to release energy.
Biosynthesis ( education) and hydrolysis ( decay) lipids in the body ( anabolism and catabolism)
Metabolism is the totality of metabolic processes in the body. All metabolic processes can be divided into catabolic and anabolic. Catabolic processes include the breakdown and breakdown of substances. In relation to lipids, this is characterized by their hydrolysis ( breakdown into simpler substances) V gastrointestinal tract. Anabolism combines biochemical reactions aimed at the formation of new, more complex substances.Lipid biosynthesis occurs in the following tissues and cells:
- Intestinal epithelial cells. Absorption of fatty acids, cholesterol and other lipids occurs in the intestinal wall. Immediately after this, new transport forms of lipids are formed in these same cells, which enter the venous blood and are sent to the liver.
- Liver cells. In liver cells, some of the transport forms of lipids will disintegrate, and new substances are synthesized from them. For example, cholesterol and phospholipid compounds are formed here, which are then excreted in bile and contribute to normal digestion.
- Cells of other organs. Some lipids travel with the blood to other organs and tissues. Depending on the cell type, lipids are converted into certain type connections. All cells, one way or another, synthesize lipids to form the cell wall ( lipid bilayer). In the adrenal glands and gonads, steroid hormones are synthesized from some lipids.
Resynthesis of lipids in the liver and other organs
Resynthesis is the process of formation of certain substances from simpler ones that were absorbed earlier. In the body, this process occurs during internal environment some cells. Resynthesis is necessary so that tissues and organs receive everything required types lipids, and not just those consumed with food. Resynthesized lipids are called endogenous. The body spends energy on their formation.At the first stage, lipid resynthesis occurs in the intestinal walls. Here, fatty acids ingested from food are converted into transport forms that are transported through the blood to the liver and other organs. Part of the resynthesized lipids will be delivered to the tissues; from the other part, substances necessary for life will be formed ( lipoproteins, bile, hormones, etc.), the excess is converted to adipose tissue and is put aside “in reserve.”
Are lipids part of the brain?
Lipids are a very important component nerve cells not only in the brain, but throughout the entire nervous system. As you know, nerve cells control various processes in the body by transmitting nerve impulses. At the same time, everything nerve pathways“isolated” from each other so that the impulse comes to certain cells and does not affect other nerve pathways. This “isolation” is possible thanks to the myelin sheath of nerve cells. Myelin, which prevents the chaotic propagation of impulses, consists of approximately 75% lipids. As in cell membranes, here they form a double layer ( bilayer), which is wrapped several times around the nerve cell.The myelin sheath in the nervous system contains the following lipids:
- phospholipids;
- cholesterol;
- galactolipids;
- glycolipids.
Lipid hormones
Lipids play an important structural role, including being present in the structure of many hormones. Hormones that contain fatty acids are called steroid hormones. In the body they are produced by the gonads and adrenal glands. Some of them are also present in adipose tissue cells. Steroid hormones take part in the regulation of many vital processes. Their imbalance can affect body weight, the ability to conceive a child, the development of any inflammatory processes, the functioning of the immune system. The key to normal production of steroid hormones is a balanced intake of lipids.Lipids are part of the following vital hormones:
- corticosteroids ( cortisol, aldosterone, hydrocortisone, etc.);
- male sex hormones - androgens ( androstenedione, dihydrotestosterone, etc.);
- female sex hormones - estrogens ( estriol, estradiol, etc.).
The role of lipids for skin and hair
Lipids are of great importance for the health of the skin and its appendages ( hair and nails). The skin contains so-called sebaceous glands, which release a certain amount of fat-rich secretion to the surface. This substance performs many useful functions.Lipids are important for hair and skin for the following reasons:
- a significant part of the hair substance consists of complex lipids;
- skin cells change rapidly, and lipids are important as an energy resource;
- secret ( secreted substance) sebaceous glands moisturizes the skin;
- Thanks to fats, the firmness, elasticity and smoothness of the skin is maintained;
- a small amount of lipids on the surface of the hair gives it a healthy shine;
- the lipid layer on the surface of the skin protects it from the aggressive effects of external factors ( cold, sun rays, microbes on the surface of the skin, etc.).
Classification of lipids
In biology and chemistry there are quite a lot various classifications lipids. The main one is chemical classification, according to which lipids are divided depending on their structure. From this point of view, all lipids can be divided into simple ones ( consisting only of oxygen, hydrogen and carbon atoms) and complex ( containing at least one atom of other elements). Each of these groups has corresponding subgroups. This classification is the most convenient, since it reflects not only the chemical structure of substances, but also partially determines the chemical properties. Biology and medicine have their own additional classifications that use other criteria.
Exogenous and endogenous lipids
All lipids in the human body can be divided into two large groups - exogenous and endogenous. The first group includes all substances that enter the body from the external environment. Largest quantity exogenous lipids enter the body with food, but there are other routes. For example, when using various cosmetics or medications, the body may also receive some lipids. Their action will be predominantly local.After entering the body, all exogenous lipids are broken down and absorbed by living cells. Here, from their structural components, other lipid compounds that the body needs will be formed. These lipids, synthesized by one's own cells, are called endogenous. They may have a completely different structure and function, but consist of the same “structural components” that entered the body with exogenous lipids. That is why, with a lack of certain types of fats in the diet, they can develop various diseases. Some components of complex lipids cannot be synthesized by the body independently, which affects the course of certain biological processes.
Fatty acid
Fatty acids are a class of organic compounds that are a structural part of lipids. Depending on which fatty acids are included in the lipid, the properties of this substance may change. For example, triglycerides, the most important source of energy for human body, are derivatives of glycerol alcohol and several fatty acids.In nature, fatty acids are found in a variety of substances - from petroleum to vegetable oils. They enter the human body mainly through food. Each acid is structural component for certain cells, enzymes or compounds. Once absorbed, the body converts it and uses it in various biological processes.
The most important sources of fatty acids for humans are:
- animal fats;
- vegetable fats;
- tropical oils ( citrus, palm, etc.);
- fats for Food Industry (margarine, etc.).
Saturated and unsaturated fatty acids
All fatty acids according to their chemical structure are divided into saturated and unsaturated. Saturated acids less beneficial for the body, and some of them are even harmful. This is explained by the fact that there are no double bonds in the molecule of these substances. These are chemically stable compounds and are less easily absorbed by the body. Currently, the connection between some saturated fatty acids and the development of atherosclerosis has been proven.Unsaturated fatty acids are divided into two large groups:
- Monounsaturated. These acids have one double bond in their structure and are therefore more active. It is believed that eating them can lower cholesterol levels and prevent the development of atherosclerosis. The greatest amount of monounsaturated fatty acids is found in a number of plants ( avocado, olives, pistachios, hazelnuts ) and, accordingly, in oils obtained from these plants.
- Polyunsaturated. Polyunsaturated fatty acids have several double bonds in their structure. Distinctive feature of these substances is that the human body is not able to synthesize them. In other words, if the body does not receive polyunsaturated fatty acids from food, over time this will inevitably lead to certain disorders. Best sources These acids are seafood, soybean and linseed oil, sesame seeds, poppy seeds, sprouted wheat, etc.
Phospholipids
Phospholipids are complex lipids containing a phosphoric acid residue. These substances, along with cholesterol, are the main components of cell membranes. These substances also take part in the transport of other lipids in the body. From a medical point of view, phospholipids can also play a signaling role. For example, they are part of bile, as they promote emulsification ( dissolution) other fats. Depending on which substance is more in bile, cholesterol or phospholipids, you can determine the risk of developing cholelithiasis.Glycerol and triglycerides
In terms of its chemical structure, glycerol is not a lipid, but it is an important structural component of triglycerides. This is a group of lipids that play a huge role in the human body. The most important function of these substances is to supply energy. Triglycerides that enter the body with food are broken down into glycerol and fatty acids. As a result, a very large amount of energy is released, which goes to work the muscles ( skeletal muscles, cardiac muscles, etc.).Adipose tissue in the human body is represented mainly by triglycerides. Most of these substances, before being deposited in adipose tissue, undergo some chemical transformations in the liver.
Beta lipids
Beta lipids are sometimes called beta lipoproteins. The duality of the name is explained by differences in classifications. This is one of the fractions of lipoproteins in the body, which plays an important role in the development of certain pathologies. First of all, we are talking about atherosclerosis. Beta lipoproteins transport cholesterol from one cell to another, but due to the structural features of the molecules, this cholesterol often “gets stuck” in the walls of blood vessels, forming atherosclerotic plaques and preventing normal blood flow. Before use, you should consult a specialist.Fat has always been regarded as a component of food that is harmful to the body, and some nutritionists are of the opinion that it is better to limit the intake of fat. But are fats really that bad for us?
In fact, fats perform several very important functions for our body, and first of all, fat is an important supplier of energy for us. We can highlight the fact that 1g of fat supplies more calories than proteins and carbohydrates in double quantity. The body does not burn all fats at once, but puts some of them in storage as a reserve to be used in the future as needed. We bring you information about fats that will help you look at fats in a new way.
Why is fat necessary for our body?
Fats supply essential fatty acids for the functioning of our body, which are involved in metabolism and are energy suppliers. In addition, fats are part of cell membranes, for example, nerve cells have membranes that are 60% fat. Thus, we can distinguish several important functions fat:
Fats are suppliers of energy material - approximately 30% of energy comes from fats,
By forming subcutaneous fatty tissue, they protect organs and tissues from mechanical damage, and also prevent heat loss,
They are carriers for vitamins A, D, E, K, as well as minerals, since without fats their absorption in the body is impossible,
They are part of cell membranes (mainly cholesterol). Without them, the cell loses its function and collapses,
Fats produce female sex hormones, which is especially important in postmenopause, when ovarian function has practically disappeared. They also play an important role during the reproductive period, as they maintain hormonal levels at the proper level. If the level of adipose tissue in the body is below 10-15%, then hormonal imbalance up to the cessation of the menstrual cycle,
Omega-6 unsaturated acid(aka arachidonic acid) is involved in the activation of blood coagulation and anticoagulation systems.
Almost 35% daily diet must consist of fats. Wherein significant role plays a type of fat.
Which fats are healthy and which are not?
Depending on the chemical structure Fats are divided into saturated and unsaturated fatty acids. Saturated fatty acids contain large amounts of hydrogen ions and are found in foods of animal origin. These are precisely the fats that are deposited on the stomach, thighs, and buttocks. This is a kind of energy reserve of the body. Saturated fats hinder growth muscle mass because they reduce the effect of insulin. But at the same time, they are the basis for the production of testosterone. When they are excluded from food, the level of this hormone, important for men, also decreases. The same can be achieved by consuming them excessively. Therefore, they are also important for the body, but in moderation.
Unsaturated fatty acids (Omega-3 and Omega-6) contain few hydrogen ions and are found mainly in animal products, such as olive or vegetable oil, fish oil. These fats are not stored in the body, but are completely burned. They are a beneficial nutritional component for the body and a raw material for the production of hormones.
There are also so-called trans fats, or artificial fats. They are filled with hydrogen ions and are found in candies and cookies, as well as in foods fast food(fast food). They are used primarily for food storage and increase the risk of developing oncological diseases and diseases of the cardiovascular system.
Omega-3 and Omega-6 are unsaturated fatty acids.
Of all types of fats, these fatty acids are the most valuable for our body. They are found in sunflower and corn oils, and rapeseed oil contains them in an ideal ratio.
Omega-3 fatty acids that are beneficial for the body are also found in flaxseed, nut and soybean oils. Salmon, mackerel and herring also contain them sufficient quantity.
Omega-3 and Omega-6 fatty acids:
Reduce the risk of developing atherosclerosis, thus preventing the development of cardiovascular diseases
Reduces cholesterol levels,
Strengthens the walls of blood vessels,
Reduce blood viscosity, thus preventing the development of blood clots,
Improve blood supply to organs and tissues, restoration of nerve cells.
Ideally, you need to mix saturated and unsaturated fats, for example, season meat dishes and salads with canola oil.
Which is better, margarine or butter?
Unlike butter, margarine contains more unsaturated fatty acids. But according to new teachings, this does not mean that the oil is more harmful. In terms of calories, both products are almost equal. But margarine contains harmful trans fats, which contribute to the growth of several diseases.
If you are a fan of margarine, then it is better to choose high-quality types with low content solid fats.
Do fats lead to obesity?
Although fat contains more calories, there is no proven link between fat intake and increased weight.
Excess calories lead to obesity: those who consume more calories than they burn gain weight. Food containing sufficient amounts of fat satiates us for a long period and allows us to eat less.
Those who, on the contrary, try to save on fats, often eat more carbohydrates. Cereal products such as White bread And pasta increase blood sugar levels, and with it insulin, which leads to the growth of adipose tissue. In addition, saturation of the body occurs quickly, but does not last long, resulting in more frequent food consumption.
Lipids - these are fat-like organic compounds, insoluble in water, but highly soluble in non-polar solvents (ether, gasoline, benzene, chloroform, etc.). Lipids belong to the simplest biological molecules.Chemically, most lipids are esters of higher carboxylic acids and a number of alcohols. The most famous among them are fats. Each fat molecule is formed by a molecule of the triatomic alcohol glycerol and the ester bonds of three molecules of higher carboxylic acids attached to it. According to the accepted nomenclature, fats are called triacyl glycerols.
Carbon atoms in molecules of higher carboxylic acids can be connected to each other by both simple and double bonds. Of the saturated (saturated) higher carboxylic acids, palmitic, stearic, and arachidic acids are most often found in fats; from unsaturated (unsaturated) - oleic and linoleic.
The degree of unsaturation and chain length of higher carboxylic acids (i.e., the number of carbon atoms) determine physical properties one kind of fat or another.
Fats with short and unsaturated acid chains have a low melting point. At room temperature These are liquids (oils) or ointment-like substances (fats). Conversely, fats with long and saturated chains of higher carboxylic acids become solid at room temperature. This is why, when hydrogenation occurs (the saturation of acid chains with hydrogen atoms at double bonds), liquid peanut butter, for example, becomes creamy and sunflower oil turns into hard margarine. Compared to the inhabitants of southern latitudes, in the body of animals living in cold climates (for example, in fish arctic seas), usually contains more unsaturated triacylglycerols. For this reason, their body remains flexible even when low temperatures.
In phospholipids, one of the extreme chains of higher carboxylic acids of triacylglycerol is replaced by a group containing phosphate. Phospholipids have polar heads and nonpolar tails. The groups forming the polar head group are hydrophilic, while the non-polar tail groups are hydrophobic. The dual nature of these lipids determines their key role in the organization of biological membranes.
Another group of lipids consists of steroids (sterols). These substances are based on cholesterol alcohol. Sterols are poorly soluble in water and do not contain higher carboxylic acids. These include bile acids, cholesterol, sex hormones, vitamin D, etc.
Lipids also include terpenes (plant growth substances - gibberellins; carotenoids - photosynthetic pigments; essential oils plants, as well as wax).
Lipids can form complexes with other biological molecules - proteins and sugars.
The functions of lipids are as follows:
Structural. Phospholipids together with proteins form biological membranes. The membranes also contain sterols.
Energy. When fats are oxidized, a large amount of energy is released, which goes towards the formation of ATP. A significant portion is stored in the form of lipids energy reserves organism, which are consumed due to lack of nutrients. Hibernating animals and plants accumulate fats and oils and use them to maintain vital processes. High content Lipids in plant seeds ensure the development of the embryo and seedling before they transition to independent nutrition. The seeds of many plants (coconut palm, castor bean, sunflower, soybean, rapeseed, etc.) serve as raw materials for obtaining vegetable oil in an industrial way.
Protective and thermal insulating. Accumulating in subcutaneous tissue and around some organs (kidneys, intestines), the fat layer protects the animal’s body and its individual organs from mechanical damage. In addition, due to low thermal conductivity, the layer of subcutaneous fat helps retain heat, which allows, for example, many animals to live in cold climates. In whales, in addition, it plays another role - it promotes buoyancy.
Lubricating and water repellent. Wax covers the skin, wool, feathers, makes them more elastic and protects them from moisture. The leaves and fruits of many plants have a waxy coating.
Regulatory. Many hormones are derivatives of cholesterol, such as sex hormones (testosterone in men and progesterone in women) and corticosteroids (aldosterone). Cholesterol derivatives, vitamin D play a key role in the metabolism of calcium and phosphorus. Bile acids are involved in the processes of digestion (emulsification of fats) and absorption of higher carboxylic acids.
Lipids are also a source of metabolic water. Oxidation of 100 g of fat produces approximately 105 g of water. This water is very important for some desert inhabitants, in particular for camels, which can do without water for 10-12 days: the fat stored in the hump is used precisely for these purposes. Bears, marmots and other hibernating animals obtain the water they need for life as a result of fat oxidation.
In the myelin sheaths of the axons of nerve cells, lipids are insulators during the conduction of nerve impulses.
Wax is used by bees to build honeycombs.
Fat-like substances lipids are components that take part in vital processes in the human body. There are several groups that perform the main functions of the body, such as the formation hormonal levels or metabolism. In this article we will explain in detail what it is and what its role is in life processes.
Lipids are organic compound, which includes fats and other fat-like substances. They actively participate in the process of cell structure and are part of membranes. Affect throughput cell membranes, as well as enzyme activity. They influence the creation of intercellular connections and a variety of chemical processes in organism. Insoluble in water, but they dissolve in solvents organic origin(such as gasoline or chloroform). In addition, there are types that are fat soluble.
This substance can be of plant or animal origin. If we are talking about plants, then most of them are in nuts and seeds. Of animal origin are mainly located in subcutaneous tissue, nervous and cerebral.
Classification of lipids
Lipids are present in almost all tissues of the body and in the blood. There are several classifications; below we present the most common one, based on the characteristics of structure and composition. According to their structure, they are divided into 3 large groups, which are subdivided into smaller ones.
The first group is simple. They include oxygen, hydrogen and carbon. They are divided into the following types:
- Fatty alcohols. Substances containing from 1 to 3 hydroxyl groups.
- Fatty acid. Found in various oils and fats.
- Fatty aldehydes. The molecule contains 12 carbon atoms.
- Triglycerides. These are precisely the fats that are deposited in the subcutaneous tissues.
- Sphingosine bases. They are located in the plasma, lungs, liver and kidneys, and are found in nerve tissues.
- Waxes. These are esters of fatty acids and high molecular weight alcohols.
- Saturated hydrocarbons. They have exclusively single bonds, with carbon atoms in a state of hybridization.
The second group is complex. They, like simple ones, include oxygen, hydrogen and carbon. But, besides them, they also contain different additional components. In turn, they are divided into 2 subgroups: polar and neutral.
Polar ones include:
- Glycolipids. They appear after combining carbohydrates with lipids.
- Phospholipids. These are esters of fatty acids, as well as polyhydric alcohols.
- Sphingolipids. They are derivatives of aliphatic amino alcohols.
Neutral ones include:
- Acylglycerides. Includes monoglycerides and diglycerides.
- N-acetylethanolamides. They are ethanolamides of fatty acids.
- Ceramides. They contain fatty acids combined with sphingosine.
- Sterol esters. They represent complex cyclic alcohols of high molecular weight. They contain fatty acids.
The third group is oxylipids. The substances appear as a result of oxygenation of polyunsaturated fatty acids. In turn, they are divided into 2 types:
- Cyclooxygenase pathway.
- Lipoxygenase pathway.
Importance for membrane cells
increase
The cell membrane is what separates the cell from the environment around it. In addition to protection, it performs quite a large number of necessary for normal life functions. The importance of lipids in the membrane cannot be overestimated.
In the cell wall, the substance forms a double layer. This helps cells interact normally with environment. Therefore, there are no problems with controlling and regulating metabolism. Membrane lipids maintain the shape of the cell.
Part of a bacterial cell
An integral part of the cell structure is bacterial lipids. As a rule, they contain waxes or phospholipids. But the amount of the substance directly varies between 5-40%. The content depends on the type of bacterium, for example, the diphtheria bacillus contains about 5%, but the tuberculosis pathogen already contains more than 30%.
A bacterial cell is different in that the substances in it are associated with other components, for example, proteins or polysaccharides. In bacteria they have many more varieties and perform many tasks:
- energy storage;
- participate in metabolic processes;
- are a component of membranes;
- cell resistance to acids depends on them;
- components of antigens.
What functions do they perform in the body?
Lipids component almost all tissues of the human body. There are different subspecies, each of which is responsible for a specific function. Next, we will dwell in more detail on the importance of the substance for life:
- Energy function. They tend to disintegrate and in the process a lot of energy appears. The body's cells need it to support processes such as air flow, substance formation, growth and respiration.
- Backup function. In the body, fats are stored in reserve; they are what make up the fatty layer of the skin. If hunger sets in, the body uses these reserves.
- Thermal insulation function. The fat layer conducts heat poorly, and therefore it is much easier for the body to maintain temperature.
- Structural function. This applies to cell membranes because the substance is a permanent component of them.
- Enzymatic function. One of the secondary functions. They help cells form enzymes and help with the absorption of certain microelements coming from outside.
- Transport function. The side effect lies in the ability of some types of lipids to transport substances.
- Signal function. It is also secondary and simply supports some body processes.
- Regulatory function. This is another mechanism that has a secondary meaning. By themselves, they are almost not involved in the regulation of various processes, but are a component of substances that directly affect them.
Thus, we can say with confidence that the functional importance of lipids for the body is difficult to overestimate. Therefore, it is important that their level is always normal. Many biological and biochemical processes in the body are tied to them.
What is lipid metabolism
Lipid metabolism is a process of physiological or biochemical nature that occurs in cells. Let's look at them in more detail:
- Triacyglycerol metabolism.
- Phospholipid metabolism. They are distributed unevenly. There are many of them in the liver and plasma (up to 50%). The half-life is 1-200 days, depending on the type.
- Cholesterol exchange. It is formed in the liver and comes with food. Excess is eliminated naturally.
- Catabolism of fatty acids. Occurs during β-oxidation; α- or ω-oxidation is less commonly involved.
- Included in the metabolic processes of the gastrointestinal tract. Namely, the breakdown, digestion and absorption of these substances coming from food. Digestion begins in the stomach with the help of an enzyme called lipase. Next, pancreatic juice and bile come into action in the intestines. The cause of malfunctions may be a violation of secretion gallbladder or pancreas.
- Lipogenesis. Simply put - the synthesis of fatty acids. Occurs in the liver or adipose tissue.
- This includes the transport of various fats from the intestines.
- Lipolysis. Catabolism, which occurs with the participation of lipase and provokes the breakdown of fats.
- Synthesis ketone bodies. Acetoacetyl-CoA gives rise to their formation.
- Interconversion of fatty acids. From fatty acids found in the liver, acids characteristic of the body are formed.
Lipids are important substance, affecting almost all areas of life. The most common triglycerides and cholesterol in the human diet. Triglycerides are an excellent source of energy; it is this type that forms fat layer bodies. Cholesterol affects the body’s metabolic processes, as well as the formation of hormonal levels. It is important that the content is always within the normal range, neither exceeding nor underestimating it. An adult needs to consume 70-140 g of lipids.
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