The main rule for maintaining health is an even distribution of the proportion of fat when serving. In fact, a person needs fat, but he must control the amount of fat consumed. A person must himself determine the amount of fat that will be useful, and not harm health. Fat needs to get on the right track to avoid the unpleasant consequences associated with weight gain, leading to heart problems, hypertension, stroke, or even death. Therefore, it is worth paying attention to foods that help burn fat. Today we will consider 10 unknown facts about fat.
On average, the average person gains 1 g of excess fat every day.... In reality, people gain more body fat. More attention should be paid to nutrition and exercise. Draw conclusions: the more fat you consume, the sooner your health problems start.
Fat cells live for another ten years after the death of a person. However, they die through physical exertion. The problem is that brain cells are constantly dying and renewing, but if fat cells take their place, memory problems occur, especially in the elderly.
8. Source of calories
In fact, fat is an irreplaceable source of calories for the body. It is vital for the maintenance of all vital processes in the body. It's worth remembering that being overweight leads to health problems.... The main rule is to choose the right foods with enough calories for the body to function.
7. Fat enhances flavor
Most preservatives and flavor enhancers are fat-based... When you mix them with food, they have a pleasant and inviting aroma and taste. If you love to cook, try adding meat or animal fat to the dish, the smell and taste of the dish will immediately change.
Fat is a kind of absorbent for vitamins. People who constantly take vitamins notice that the effect of vitamins is weaker after eating. Especially if the vitamins are in a soluble form.
5. Women need fat more than men
First of all, the great need for fats in women is associated with nature. A woman is a mother, in order to conceive a child, the body needs strength to carry a child and raise him in the womb, the body burns calories and fats, and, finally, after the birth of a child, a woman breastfeeds, and the basis of milk is lactose and fat. Fat reserves in a woman's body are explained by the fact that the body stores energy for the expectant mother. Therefore, many women lose weight after breastfeeding.
There are two types of fat. Figuratively they are called good and bad. Good fat is referred to as unsaturated fat, such fats are necessary for the human body. They are found in lean white meats and steamed foods such as fish. Bad fats are fatty meats, chicken skin, or dairy products. The consumption of these foods leads to high cholesterol and heart problems.
Since fat contains a high level of calories, they are stored for energy.... Consuming 1 gram of fat equals 9 calories.
2. Fat storage
Fat, which is essential for health, is stored in the muscles, bone marrow and organs of the nervous system. It is essential for the production of hormones and boosting immunity. Subcutaneous fat is an indicator that it's time to lose weight. Fat is found in foods that increase muscle mass.
Women should maintain 13 to 17% body fat which are usually stored in the thighs, chest, thighs and abdomen. In men, fat is stored in the belly. They must maintain a body fat percentage of 3 to 5%, which is significantly less than that of women.
Fat has always been regarded as a harmful component of food for the body and some nutritionists are of the opinion that it is better to limit the intake of fat. But are fats so bad for us?
In reality, 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 1 g of fat delivers more calories than proteins and carbohydrates in double the amount. The body does not burn all the fats at once, but stores some of it in the depot as a reserve in order to use it in the future as needed. We have provided you with information on fats that will help you look at fats in a new way.
Why is fat necessary for our body?
Fats supply fatty acids important for the life of our body, which are involved in metabolism and are energy suppliers. In addition, fats are part of the cell membranes, for example, nerve cells have membranes that are 60% fat. Thus, several important functions of fats can be distinguished:
Fats are the providers of energy material - approximately 30% of the energy comes from fats,
By forming subcutaneous fat, 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 for minerals, since their absorption in the body is impossible without fats,
They are part of the cell walls (mainly cholesterol). Without them, the cell loses its function and collapses,
Fats produce female sex hormones, which is especially important in postmenopausal women, when the function of the ovaries has practically died out. They also play an important role in the reproductive period, since they maintain the hormonal background at the proper level. If the level of adipose tissue in the body is below 10-15%, then hormonal imbalance occurs up to the termination of the menstrual cycle,
Omega-6 unsaturated acid (also known as arachidonic acid) is involved in the activation of the blood coagulation and anticoagulation systems.
Almost 35% of the daily diet should be fat. In this case, the type of fat plays a significant role.
Which fats are good and which are not?
Depending on the chemical structure, fats are divided into saturated and unsaturated fatty acids. Saturated fatty acids are high in hydrogen ions and are found in animal foods. These are exactly the fats that are deposited on the stomach, thighs, buttocks. This is a kind of energy reserve of the body. Saturated fat inhibits muscle growth by reducing the effects of insulin. But at the same time, they are the basis for the production of testosterone. If they are excluded from food, the level of this hormone, which is important for men, also decreases. The same can be obtained with excessive consumption. 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, for example, olive oil, vegetable oil, fish oil. These fats are not stored in the body, but are completely burned. They are a useful component of nutrition for the body, raw materials for the production of hormones.
There are also so-called trans fats, or artificial fats. They are packed with hydrogen ions and are found in candy and biscuits, as well as fast food (fast food). They are used mainly for storing food and they increase the risk of developing cancer and diseases of the cardiovascular system.
Omega-3 and Omega-6 unsaturated fatty acids.
Of all types of fats, it is these fatty acids that 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 to the body are also found in flaxseed, nut and soybean oils. Salmon, mackerel, and herring also contain plenty of them.
Omega-3 and Omega-6 fatty acids:
Reduces the risk of developing atherosclerosis, thus preventing the development of cardiovascular diseases
Reduce cholesterol levels,
Strengthen the walls of blood vessels,
Reduce blood viscosity, thus preventing the development of blood clots,
Improves the blood supply to organs and tissues, the restoration of nerve cells.
Ideally, you should mix saturated and unsaturated fats, for example, season meats and salads with rapeseed oil.
Which is better, margarine or butter?
In contrast to butter, margarine contains more unsaturated fatty acids. But according to new teachings, this does not mean that oil is more harmful. In terms of calories, both foods are almost equal. But margarine contains unhealthy trans fats that have been linked to a number of diseases.
If you are a fan of margarine, then go for the high quality, low solid fat varieties.
Does fat lead to obesity?
Despite the fact that fat contains more calories, there is no proven link between fat consumption and increased weight.
An excess of calories leads to obesity: those who consume more calories than they burn, gain weight. Foods that are high in fat will lead to long-term satiety and allow us to eat less.
On the contrary, who tries to save on fats, they often eat more carbohydrates. Grain foods such as white bread and pasta raise blood sugar, and with it insulin, which leads to an increase in adipose tissue. In addition, the saturation of the body occurs quickly, but not for a long time, as a result of which it leads to more frequent food consumption.
Lipids- Substances that are very heterogeneous in their chemical structure, characterized by different solubility in organic solvents and, as a rule, insoluble in water. They play an important role in life processes. As one of the main components of biological membranes, lipids affect their permeability, participate in the transmission of nerve impulses, and the creation of intercellular contacts.
Other functions of lipids are the formation of an energy reserve, the creation of protective water-repellent and thermal insulating covers in animals and plants, the protection of organs and tissues from mechanical influences.
CLASSIFICATION OF LIPIDS
Depending on the chemical composition, lipids are divided into several classes.
- Simple lipids include substances whose molecules consist only of residues of fatty acids (or aldehydes) and alcohols. These include
- fats (triglycerides and other neutral glycerides)
- waxes
- Complex lipids
- derivatives of phosphoric acid (phospholipids)
- lipids containing sugar residues (glycolipids)
- sterols
- sterides
In this section, lipid chemistry will be considered only to the extent that is necessary for understanding lipid metabolism.
If an animal or plant tissue is treated with one or more (more often sequentially) organic solvents, such as chloroform, benzene or petroleum ether, then some of the material goes into solution. The components of this soluble fraction (extract) are called lipids. The lipid fraction contains substances of various types, most of which are shown in the diagram. Note that due to the heterogeneity of the components included in the lipid fraction, the term "lipid fraction" cannot be regarded as a structural characteristic; it is only a working laboratory name for the fraction obtained from the extraction of biological material with low-polarity solvents. Nevertheless, most lipids share some common structural features that determine their important biological properties and similar solubility.
Fatty acid
Fatty acids - aliphatic carboxylic acids - in the body can be in a free state (trace amounts in cells and tissues) or serve as building blocks for most classes of lipids. Over 70 different fatty acids have been isolated from the cells and tissues of living organisms.
Fatty acids found in natural lipids contain an even number of carbon atoms and have a predominantly unbranched carbon chain. Below are the formulas for the most commonly found natural fatty acids.
Natural fatty acids, although somewhat conditionally, can be divided into three groups:
- saturated fatty acids [show]
- monounsaturated fatty acids [show]
Monounsaturated (with one double bond) fatty acids:
- polyunsaturated fatty acids [show]
Polyunsaturated (with two or more double bonds) fatty acids:
In addition to these main three groups, there is also a group of so-called unusual natural fatty acids [show] .
The fatty acids that make up the lipids of animals and higher plants have many properties in common. As already noted, almost all natural fatty acids contain an even number of carbon atoms, most often 16 or 18. Unsaturated fatty acids of animals and humans, which are involved in the construction of lipids, usually contain a double bond between the 9th and 10th carbon, additional double bonds, such as usually occur between the 10th carbon and the methyl end of the chain. The counting comes from the carboxyl group: the C-atom closest to the COOH group is designated as α, the adjacent one is β, and the terminal carbon atom in the hydrocarbon radical is ω.
The peculiarity of double bonds of natural unsaturated fatty acids lies in the fact that they are always separated by two simple bonds, that is, there is always at least one methylene group between them (-CH = CH-CH 2 -CH = CH-). Such double bonds are referred to as "isolated". Naturally occurring unsaturated fatty acids have a cis configuration and are extremely rare in a trans configuration. It is believed that in unsaturated fatty acids with several double bonds, the cis-configuration gives the hydrocarbon chain a curved and shortened appearance, which makes biological sense (especially when you consider that many lipids are part of membranes). In microbial cells, unsaturated fatty acids usually contain one double bond.
Long chain fatty acids are practically insoluble in water. Their sodium and potassium salts (soaps) form micelles in water. In the latter, negatively charged carboxyl groups of fatty acids face the aqueous phase, and non-polar hydrocarbon chains are hidden inside the micellar structure. Such micelles have a total negative charge and remain suspended in solution due to mutual repulsion (Fig. 95).
Neutral fats (or glycerides)
Neutral fats are esters of glycerin and fatty acids. If all three hydroxyl groups of glycerol are esterified with fatty acids, then such a compound is called triglyceride (triacylglycerol), if two - diglyceride (diacylglycerol) and, finally, if one group is esterified - monoglyceride (monoacylglycerol).
Neutral fats are found in the body either in the form of protoplasmic fat, which is a structural component of cells, or in the form of reserve, reserve fat. The role of these two forms of fat in the body is not the same. Protoplasmic fat has a constant chemical composition and is contained in tissues in a certain amount, which does not change even with morbid obesity, while the amount of reserve fat is subject to large fluctuations.
The bulk of natural neutral fats are triglycerides. The fatty acids in triglycerides can be saturated or unsaturated. Palmitic, stearic and oleic acids are more common among fatty acids. If all three acid radicals belong to the same fatty acid, then such triglycerides are called simple (for example, tripalmitin, tristearin, triolein, etc.), if they are different fatty acids, then they are called mixed. Mixed triglycerides are named from their constituent fatty acids; the numbers 1, 2 and 3 indicate the bond of the fatty acid residue with the corresponding alcohol group in the glycerol molecule (for example, 1-oleo-2-palmitostearin).
Fatty acids that make up triglycerides practically determine their physicochemical properties. Thus, the melting point of triglycerides increases with an increase in the number and length of saturated fatty acid residues. In contrast, the higher the content of unsaturated fatty acids or short-chain acids, the lower the melting point. Animal fats (lard) usually contain a significant amount of saturated fatty acids (palmitic, stearic, etc.), due to which they are solid at room temperature. Fats, which contain many mono- and polyunsaturated acids, are liquid at ordinary temperatures and are called oils. So, in hemp oil, 95% of all fatty acids are oleic, linoleic and linolenic acids, and only 5% are stearic and palmitic acids. Note that human fat melting at 15 ° C (it is liquid at body temperature) contains 70% oleic acid.
Glycerides are able to enter into all chemical reactions inherent in esters. Of greatest importance is the saponification reaction, as a result of which glycerol and fatty acids are formed from triglycerides. Saponification of fat can occur both by enzymatic hydrolysis and by the action of acids or alkalis.
Alkaline cleavage of fat by the action of caustic soda or caustic potash is carried out in the industrial production of soap. Let us recall that soap is sodium or potassium salts of higher fatty acids.
The following indicators are often used to characterize natural fats:
- iodine number - the number of grams of iodine, which, under certain conditions, binds 100 g of fat; this number characterizes the degree of unsaturation of fatty acids present in fats, the iodine number of beef fat 32-47, lamb 35-46, pork 46-66;
- acid number - the number of milligrams of caustic potassium required to neutralize 1 g of fat. This number indicates the amount of free fatty acids present in the fat;
- saponification number - the number of milligrams of caustic potassium consumed to neutralize all fatty acids (both included in triglycerides and free) contained in 1 g of fat. This number depends on the relative molecular weight of the fatty acids that make up the fat. The saponification number for the main animal fats (beef, lamb, pork) is practically the same.
Waxes are esters of higher fatty acids and higher monohydric or dihydric alcohols with the number of carbon atoms from 20 to 70. Their general formulas are shown in the diagram, where R, R "and R" are possible radicals.
Waxes can be part of the fat that covers the skin, wool, feathers. In plants, 80% of all lipids that form a film on the surface of leaves and trunks are waxes. It is also known that waxes are normal metabolites of some microorganisms.
Natural waxes (for example, beeswax, spermaceti, lanolin) usually contain, in addition to the aforementioned esters, a certain amount of free higher fatty acids, alcohols and hydrocarbons with a carbon number of 21-35.
Phospholipids
This class of complex lipids includes glycerophospholipids and sphingolipids.
Glycerophospholipids are derivatives of phosphatidic acid: they contain glycerol, fatty acids, phosphoric acid, and usually nitrogen-containing compounds. The general formula of glycerophospholipids is shown in the diagram, where R 1 and R 2 are radicals of higher fatty acids, and R 3 is a radical of a nitrogenous compound.
It is characteristic of all glycerophospholipids that one part of their molecule (radicals R 1 and R 2) exhibits pronounced hydrophobicity, while the other part is hydrophilic due to the negative charge of the phosphoric acid residue and the positive charge of the radical R 3.
Of all lipids, glycerophospholipids have the most pronounced polar properties. When glycerophospholipids are placed in water, only a small part of them passes into a true solution, while the bulk of the "dissolved" lipid is in aqueous systems in the form of micelles. There are several groups (subclasses) of glycerophospholipids.
- [show]
.
- Phosphatidylserines [show]
.
In the phosphatidylserine molecule, the nitrogenous compound is the serine amino acid residue.
Phosphatidylserines are much less widespread than phosphatidylcholines and phosphatidylethanolamines, and their importance is determined mainly by the fact that they are involved in the synthesis of phosphatidylethanolamines.
- Plasmalogens (acetal phosphatides) [show]
.
They differ from the glycerophospholipids discussed above in that instead of one higher fatty acid residue, they contain a fatty acid aldehyde residue, which is linked to the hydroxyl group of glycerol by an unsaturated ester bond:
Thus, during hydrolysis, plasmalogen decomposes into glycerol, higher fatty acid aldehyde, fatty acid, phosphoric acid, choline, or ethanolamine.
[show]
.
Unlike triglycerides in the phosphatidylcholine molecule, one of the three hydroxyl groups of glycerol is associated not with fatty acid, but with phosphoric acid. In addition, phosphoric acid, in turn, is linked with an ether bond with a nitrogenous base [HO-CH 2 -CH 2 -N + = (CH 3) 3] - choline. Thus, glycerol, higher fatty acids, phosphoric acid and choline are combined in the phosphatidylcholine molecule.
[show] .
The main difference between phosphatidylcholines and phosphatidylethanolamines is that the latter include the nitrogenous base ethanolamine (HO-CH 2 -CH 2 -NH 3 +) instead of choline.
Of the glycerophospholipids in the body of animals and higher plants, phosphatidylcholines and phosphatidylethanolamines are found in the greatest amount. These two groups of glycerophospholipids are metabolically linked to each other and are the main lipid components of cell membranes.
The R 3 -radical in this group of glycerophospholipids is a six-carbon sugar alcohol - inositol:
Phosphatidylinositols are quite widespread in nature. They are found in animals, plants and microbes. In the animal body, they are found in the brain, liver and lungs.
[show] . 
It should be noted that free phosphatidic acid is found in nature, although in comparison with other glycerophospholipids in relatively small quantities.
Cardiolilin belongs to glycerophospholipids, more precisely to polyglycerol phosphates. The backbone of the cardiolipin molecule includes three glycerol residues connected to each other by two phosphodiester bridges through positions 1 and 3; the hydroxyl groups of the two outer glycerol residues are esterified with fatty acids. Cardiolipin is part of the mitochondrial membranes. Table 29 summarizes the data on the structure of the main glycerophospholipids.
Among the fatty acids that make up glycerophospholipids, both saturated and unsaturated fatty acids (more often stearic, palmitic, oleic and linoleic) are found.
It was also found that most phosphatidylcholines and phosphatidylethanolamines contain one saturated higher fatty acid esterified at position 1 (at the 1st carbon atom of glycerol), and one unsaturated higher fatty acid esterified at position 2. Hydrolysis of phosphatidylcholines and phosphatidylethanolamines with the participation of specific enzymes , for example, in the venom of cobra, which belong to phospholipases A 2, leads to the elimination of unsaturated fatty acids and the formation of lysophosphatidylcholines or lysophosphatidylethanolamines with a strong hemolytic effect.
Sphingolipids
Glycolipids
Complex lipids containing carbohydrate groups in the molecule (more often a D-galactose residue). Glycolipids play an essential role in the functioning of biological membranes. They are found predominantly in brain tissue, but they are also found in blood cells and other tissues. There are three main groups of glycolipids:
- cerebrosides
- sulfatides
- gangliosides
Cerebrosides contain neither phosphoric acid nor choline. They include hexose (usually D-galactose), which is linked by an ether bond to the hydroxyl group of the amino alcohol sphingosine. In addition, a fatty acid is a part of cerebroside. Among these fatty acids, the most common are lignoceric, nervous and cerebronic acids, i.e. fatty acids having 24 carbon atoms. The structure of cerebrosides can be represented by the diagram. Cerebrosides can also be classified as sphingolipids, since they contain the alcohol sphingosine.
The most studied representatives of cerebrosides are the nerve containing neurotic acid, the cerebron, which contains cerebronic acid, and kerazine, which contains lignocyric acid. The content of cerebrosides is especially high in the membranes of nerve cells (in the myelin sheath).
Sulfatides differ from cerebrosides in that they contain a sulfuric acid residue in the molecule. In other words, the sulfatide is a cerebroside sulfate in which the sulfate is esterified at the third carbon atom of the hexose. In the mammalian brain, sulfatides, like cerebrosides, are found in the white matter. However, their content in the brain is much lower than that of cerebrosides.
During the hydrolysis of gangliosides, one can find higher fatty acid, sphingosine alcohol, D-glucose and D-galactose, as well as derivatives of amino sugars: N-acetylglucosamine and N-acetylneuraminic acid. The latter is synthesized in the body from glucosamine.
Structurally, gangliosides are largely similar to cerebrosides, with the only difference that instead of one galactose residue they contain a complex oligosaccharide. One of the simplest gangliosides is hematoside, isolated from the stroma of erythrocytes (scheme)
Unlike cerebrosides and sulfatides, gangliosides are found mainly in the gray matter of the brain and are concentrated in the plasma membranes of nerve and glial cells.
All the lipids considered above are usually called saponifiable, since soaps are formed during their hydrolysis. However, there are lipids that are not hydrolyzed to release fatty acids. These lipids include steroids.
Steroids are naturally occurring compounds. They are derivatives of the core containing three fused cyclohexane and one cyclopentane ring. Steroids include numerous substances of a hormonal nature, as well as cholesterol, bile acids and other compounds.
In the human body, sterols occupy the first place among steroids. The most important representative of sterols is cholesterol:
It contains an alcoholic hydroxyl group at C 3 and a branched aliphatic chain of eight carbon atoms at C 17. The hydroxyl group at C 3 can be esterified with a higher fatty acid; in this case, cholesterol esters (cholesterides) are formed:
Cholesterol plays the role of a key intermediate in the synthesis of many other compounds. Plasma membranes of many animal cells are rich in cholesterol; in a significantly smaller amount, it is contained in the membranes of mitochondria and in the endoplasmic reticulum. Note that there is no cholesterol in plants. Plants have other sterols known collectively as phytosterols.
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What are lipids?
Lipids are one of the groups of organic compounds of great importance for living organisms. According to their chemical structure, all lipids are divided into simple and complex. The molecule of simple lipids is composed of alcohol and bile acids, while complex lipids also contain other atoms or compounds. In general, lipids are of great importance to humans. These substances are found 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 the Greek root meaning "fat", but these definitions still have some differences. Lipids are a broader group of substances, while fats are understood to mean only some types of lipids. The synonym for "fats" is "triglycerides", which are obtained from the combination of alcohol, glycerol 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 found in almost all body tissues. Their molecules are in any living cell, and without these substances life is simply impossible. There are many different lipids found in the human body. Each kind or class of these compounds has its own functions. Many biological processes depend on the normal intake and formation of lipids. From the point of view of biochemistry, lipids are involved in the following important processes:
- energy production by the body;
- cell division;
- transmission of nerve impulses;
- the formation of blood components, hormones and other important substances;
- protection and fixation of some internal organs;
- cell division, respiration, etc.
The biological role of lipids in a living cell
Lipid molecules perform a huge number of functions not only on the scale of the whole organism, but also in each living cell separately. In fact, a cell is a structural unit of a living organism. It contains assimilation and synthesis ( education) certain substances. Some of these substances are used to maintain the vital activity of the cell itself, some - for cell division, and some - for 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 energetic 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. When needed, 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 fat. Most of their volume is occupied by a large drop of fat. It is from adipocytes that adipose tissue in the body consists. The largest reserves of adipose tissue are found in the subcutaneous fat, the greater and lesser omentum ( in the abdominal cavity). With prolonged fasting, adipose tissue gradually breaks down, since lipid reserves are used to obtain energy.Also, adipose tissue deposited in the subcutaneous fat provides thermal insulation. Lipid-rich tissues are generally less conductive to heat. This allows the body to maintain a constant body temperature and not so quickly cool or overheat in different environmental conditions.
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. Thanks to this, a living cell can perform its functions and regulate metabolism with the external environment. The lipids that form the cell membrane also help maintain the shape of the cell.Why do lipids-monomers form a double layer ( bilayer)?
Monomers are chemicals ( in this case - molecules), which are capable of connecting to form more complex connections. 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). A double layer is obtained due to the fact that lipid molecules are deployed with hydrophilic parts inside the cell and outside. The hydrophobic parts are practically in contact, since they are located between two layers. Other molecules ( 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 a few connections perform it. For example, lipoproteins, which are made up of lipids and proteins, carry substances in the blood from one organ to another. However, this function is rarely isolated, apart from considering it 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 a significant amount of phospholipids and cholesterol. They neutralize excess pancreatic enzymes and prevent them from damaging intestinal cells. Also, dissolution occurs in bile ( emulsification) exogenous lipids from food. Thus, lipids play a huge role in digestion and aid in the work of other enzymes, although they are not enzymes in themselves.Signal function
Some of the complex lipids have a signaling function in the body. It consists in maintaining various processes. For example, glycolipids in nerve cells are involved in the transmission of nerve impulses from one nerve cell to another. In addition, the signals within the cell itself are of great importance. She needs to "recognize" substances coming from 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, and affect the functioning of the immune system. Also lipids are part of prostaglandins. These substances are produced during inflammatory processes and affect some processes in the nervous system ( e.g. perception of pain).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, the 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 generate energy.Also, lipids to one degree or another are associated with the metabolism of the following substances:
- Adenosine triphosphoric acid ( ATF). ATP is a kind of unit of energy inside the 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 the building blocks of DNA and are found in the nuclei of living cells. The energy generated by the breakdown of fats is partly used for cell division. During division, new DNA strands are formed from nucleic acids.
- Amino acids. Amino acids are the building blocks of proteins. In combination with lipids, they form complex complexes, lipoproteins, which are responsible for the transport of substances in the body.
- Steroids. Steroids are a type of hormone that contains significant amounts of lipids. With poor absorption of lipids from food, the patient may have problems with the endocrine system.
Digestion and absorption of lipids ( metabolism, metabolism)
The digestion and absorption of lipids is the first step in the metabolism of these substances. The main part of lipids enters the body with food. In the oral cavity, food is chopped and mixed with saliva. Further, the lump enters the stomach, where chemical bonds are partially destroyed by the action of hydrochloric acid. Also, some chemical bonds in lipids are destroyed by the lipase enzyme contained in saliva.Lipids are insoluble in water, so in the duodenum they are not immediately digested by enzymes. First, the so-called fat emulsification takes place. After that, the chemical bonds are cleaved by lipase coming from the pancreas. In principle, for each type of lipid, its own enzyme is now defined, which is responsible for the breakdown and assimilation of this substance. For example, phospholipase breaks down phospholipids, cholesterol esterase - cholesterol compounds, etc. All of these enzymes are found in varying amounts in pancreatic juice.
The cleaved lipid fragments are absorbed separately by the cells of the small intestine. In general, the digestion of fats is a very complex process that is regulated by many hormones and hormone-like substances.
What is lipid emulsification?
Emulsification is the incomplete dissolution of fatty substances in water. In the food lump that enters the duodenum, fats are contained in the form of large drops. This prevents them from interacting with enzymes. In the process of emulsification, large fat droplets are "crushed" into smaller droplets. As a result, the area of contact between the fat droplets and the surrounding water-soluble substances increases, and lipid breakdown becomes possible.The process of emulsifying lipids in the 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 promote their "crushing" into small droplets.
- Bile secreted from the liver accumulates in the gallbladder. Here she concentrates and stands out as needed.
- When fatty foods are consumed, a signal is sent to the smooth muscles of the gallbladder to contract. As a result, a portion of bile is secreted through the bile ducts into the duodenum.
- In the duodenum, the actual emulsification of fats and their interaction with pancreatic enzymes occurs. The contractions in the walls of the small intestine facilitate this process by "mixing" the contents.
Enzymes for the breakdown of lipids
For the digestion of each substance, the body has its own enzymes. Their task is to destroy chemical bonds between molecules ( or between atoms in molecules) so that nutrients can be normally absorbed by the body. Different enzymes are responsible for the breakdown of different lipids. Most of them are found in the juice secreted by the pancreas.The following groups of enzymes are responsible for the breakdown of lipids:
- lipase;
- phospholipases;
- cholesterol esterase, etc.
What vitamins and hormones are involved in lipid regulation?
Most lipids in human blood are relatively constant. It can fluctuate within certain limits. It depends on the biological processes occurring in the body itself, and on a number of external factors. The regulation of blood lipids is a complex biological process that involves many different organs and substances.The following substances play the greatest role in the assimilation and maintenance of a constant lipid level:
- Enzymes. A number of pancreatic enzymes are involved in the breakdown of lipids that enter 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. Normal lipid assimilation is also impossible without these substances.
- Vitamins. Vitamins have a complex strengthening effect on the body and directly or indirectly also affect lipid metabolism. For example, with a lack of vitamin A, the regeneration of cells in the mucous membranes worsens, and the digestion of substances in the intestine also slows down.
- Intracellular enzymes. The cells of the intestinal epithelium 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 insulin levels can have a profound effect on blood lipid levels. That is why some norms have been revised for patients with diabetes mellitus. Thyroid hormones, glucocorticoid hormones, or norepinephrine can stimulate the breakdown of adipose tissue with the release of energy.
Biosynthesis ( education) and hydrolysis ( decay) lipids in the body ( anabolism and catabolism)
Metabolism is a set of metabolic processes in the body. All metabolic processes can be divided into catabolic and anabolic. The catabolic processes include the breakdown and decay of substances. For lipids, this is characterized by their hydrolysis ( decay into simpler substances) in the 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 the 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 break down, and new substances are synthesized from them. For example, the formation of compounds of cholesterol and phospholipids occurs here, which are then excreted in the bile and contribute to normal digestion.
- Cells of other organs. Part of the lipids passes through the blood to other organs and tissues. Depending on the type of cells, lipids are converted into a certain type of compound. All cells, one way or another, synthesize lipids to form a cell wall ( lipid bilayer). In the adrenal glands and gonads, steroid hormones are synthesized from part of the lipids.
Resynthesis of lipids in the liver and other organs
Resynthesis is the process of formation of certain substances from simpler ones that were assimilated earlier. In the body, this process takes place in the internal environment of some cells. Resynthesis is necessary in order for tissues and organs to receive all the necessary types of lipids, and not just those that were 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, the fatty acids supplied with food are converted into transport forms, which are sent with the blood to the liver and other organs. Part of the resynthesized lipids will be delivered to the tissues, from the other part, the substances necessary for vital activity are formed ( lipoproteins, bile, hormones, etc.), the excess is converted into adipose tissue and stored "in reserve".
Are lipids part of the brain?
Lipids are a very important constituent of 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. In this case, all nerve pathways are "isolated" from each other so that the impulse comes to certain cells and does not affect other nerve pathways. This "isolation" is possible due to the myelin sheath of nerve cells. Myelin, which prevents the chaotic propagation of impulses, is approximately 75% lipids. As in cell membranes, here they form a double layer ( bilayer), which is wrapped around the nerve cell several times.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 the cells of adipose tissue. Steroid hormones are involved 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, and the functioning of the immune system. The key to normal production of steroid hormones is a balanced intake of lipids.Lipids are found in 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 in skin and hair
Lipids are of great importance for the health of the skin and its appendages ( hair and nails). The skin contains the so-called sebaceous glands, which secrete to the surface a certain amount of secretion, rich in fats. This substance has many beneficial 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) the sebaceous glands moisturize the skin;
- thanks to fats, the firmness, elasticity and smoothness of the skin are maintained;
- a small amount of lipids on the surface of the hair gives it a healthy shine;
- the lipid layer on the skin surface protects it from the aggressive effects of external factors ( cold, sun rays, microbes on the surface of the skin, etc.).
Lipid classification
In biology and chemistry, there are quite a few different classifications of 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 ( composed only of oxygen, hydrogen and carbon atoms) and complex ( including at least one atom of other elements). Each of these groups has corresponding subgroups. This classification is 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 using 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. The largest amount of exogenous lipids enters the body with food, but there are other ways. For example, when using various cosmetics or drugs, the body can also receive some amount of 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 will be formed, which the body needs. These lipids, synthesized by their own cells, are called endogenous. They may have a completely different structure and function, but they 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 food, various diseases can develop. Some of the components of complex lipids cannot be synthesized by the body on its own, which is reflected in the course of certain biological processes.
Fatty acid
Fatty acids is a class of organic compounds that are the structural part of lipids. Depending on what kind of fatty acids are part of the lipid, the properties of this substance may change. For example, triglycerides, the most important source of energy for the human body, are derivatives of glycerol alcohol and several fatty acids.Naturally, fatty acids are found in a wide variety of substances, from petroleum to vegetable oils. They enter the human body mainly with food. Each acid is a structural component for specific 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 the food industry ( margarine, etc.).
Saturated and unsaturated fatty acids
All fatty acids by their chemical structure are divided into saturated and unsaturated. Saturated acids are less beneficial for the body, and some of them are even harmful. This is due to the fact that there are no double bonds in the molecule of these substances. These are chemically stable compounds, and they are less well absorbed by the body. Currently, the connection of some saturated fatty acids with 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 thus more active. It is believed that eating them can lower cholesterol levels and prevent the development of atherosclerosis. The largest 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. A distinctive feature of these substances is that the human body is not able to synthesize them. In other words, if polyunsaturated fatty acids do not enter the body with food, over time this will inevitably lead to certain disorders. The best sources of these acids are seafood, soybean and flaxseed oil, sesame seeds, poppy seeds, wheat germ, and more.
Phospholipids
Phospholipids are complex lipids containing a phosphoric acid residue. These substances, along with cholesterol, are the main component of cell membranes. Also, these substances are involved 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 the bile, cholesterol or phospholipids, you can determine the risk of developing gallstone disease.Glycerin and triglycerides
In terms of 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 the supply of 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, heart 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 due to differences in classifications. This is one of the lipoprotein fractions 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 characteristics of the molecules, this cholesterol often "gets stuck" in the walls of blood vessels, forming atherosclerotic plaques and interfering with normal blood flow. Before use, you must consult a specialist.What are lipids, what is the classification of lipids, what is their structure and function? The answer to this and many other questions is provided by biochemistry, which studies these and other substances that are of great importance for metabolism.
What it is
Lipids are organic substances that do not dissolve in water. The functions of lipids in the human body are diverse.
Lipids - this word means "small particles of fat"
This is primarily:
- Energy. Lipids serve as a substrate for storing and using energy. The breakdown of 1 gram of fat releases about 2 times more energy than the breakdown of protein or carbohydrates of the same weight.
- Structural function. The structure of lipids determines the structure of the cell membranes in our body. They are arranged in such a way that the hydrophilic part of the molecule is inside the cell, and the hydrophobic part is on its surface. Due to these properties of lipids, each cell, on the one hand, is an autonomous system, fenced off from the outside world, and on the other hand, each cell can exchange molecules with others and with the environment using special transport systems.
- Protective. The surface layer that we have on the skin and serves as a kind of barrier between us and the outside world is also composed of lipids. In addition, they, in the composition of adipose tissue, provide the function of thermal insulation and protection from harmful external influences.
- Regulatory. They are part of vitamins, hormones and other substances that regulate many processes in the body.
The general characteristics of lipids are based on structural features. They have twofold properties, since they have soluble and insoluble parts in the molecule.
Intake of the body
Lipids partly enter the human body with food, partly they are able to synthesize endogenously. The splitting of the main part of dietary lipids occurs in the duodenum 12 under the influence of pancreatic juice secreted by the pancreas and bile acids in the bile. Having split, they are resynthesized again in the intestinal wall and, already in the composition of special transport particles ─ lipoproteins, ─ are ready to enter the lymphatic system and the general bloodstream.
With food, a person needs to get about 50-100 grams of fat every day, which depends on the state of the body and the level of physical activity.
Classification
The classification of lipids, depending on their ability to form soaps under certain conditions, divides them into the following classes of lipids:
- Saponified. The so-called substances that, in an environment with an alkaline reaction, form salts of carboxylic acids (soaps). This group includes simple lipids, complex lipids. Both simple and complex lipids are important for the body, they have a different structure and, accordingly, lipids perform different functions.
- Unsaponifiables. They do not form carboxylic acid salts in an alkaline medium. This biological chemistry includes fatty acids, derivatives of polyunsaturated fatty acids ─ eicosanoids, cholesterol, as the most prominent representative of the main class of sterols-lipids, as well as its derivatives ─ steroids and some other substances, for example, vitamins A, E, etc.
General classification of lipids
Fatty acid
Substances that belong to the group of so-called simple lipids and are of great importance for the body are fatty acids. Depending on the presence of double bonds in the non-polar (water-insoluble) carbon "tail", fatty acids are divided into saturated (do not have double bonds) and unsaturated (have one or even more double carbon-carbon bonds). Examples of the first: stearic, palmitic. Examples of unsaturated and polyunsaturated fatty acids: oleic, linoleic, etc.
It is the unsaturated fatty acids that are especially important for us and must be taken with food.
Why? Because they:
- Serve as a component for the synthesis of cell membranes, participate in the formation of many biologically active molecules.
- They help to maintain the normal functioning of the endocrine and reproductive systems.
- They help prevent or slow down the development of atherosclerosis and many of its consequences.
Fatty acids are divided into two large groups: unsaturated and saturated
Inflammatory mediators and more
Another type of simple lipids are such important mediators of internal regulation as eicosanoids. They have a unique (like almost everything in biology) chemical structure and, accordingly, unique chemical properties. The main basis for the synthesis of eicosanoids is arachidonic acid, which is one of the most important unsaturated fatty acids. It is eicosanoids that are responsible in the body for the course of inflammatory processes.
Their role in inflammation can be briefly described as follows:
- They change the permeability of the vascular wall (namely, increase its permeability).
- Stimulates the release of leukocytes and other cells of the immune system into the tissue.
- With the help of chemicals, they mediate the movement of immune cells, the release of enzymes and the absorption of particles foreign to the body.
But the role of eicosanoids in the human body does not end there, they are also responsible for the blood coagulation system. Depending on the developing situation, eicosanoids can dilate blood vessels, relax smooth muscles, reduce aggregation, or, if necessary, cause opposite effects: vasoconstriction, contraction of smooth muscle cells and thrombus formation.
Eicosanoids - a large group of physiologically and pharmacologically active compounds
Studies were carried out according to which people who received sufficient amounts of the main substrate for the synthesis of eicosanoids ─ arachidonic acid ─ with food (found in fish oil, fish, vegetable oils) suffered less from diseases of the cardiovascular system. Most likely, this is due to the fact that such people have a more perfect exchange of eicosanoids.
Substances of a complex structure
Complex lipids are a group of substances that are no less important for the body than simple lipids. The main properties of this group of fats:
- Participate in the formation of cell membranes, along with simple lipids, and also provide intercellular interactions.
- They are part of the myelin sheath of nerve fibers, which is necessary for the normal transmission of nerve impulses.
- They are one of the important components of a surfactant ─ a substance that ensures breathing processes, namely, prevents the alveoli from collapsing during exhalation.
- Many of them play the role of receptors on the cell surface.
- The significance of some complex fats secreted from cerebrospinal fluid, nervous tissue, and heart muscle is not fully understood.
The simplest representatives of this group of lipids include phospholipids, glyco- and sphingolipids.
Cholesterol
Cholesterol is a substance of a lipid nature with the most important value in medicine, since the violation of its metabolism negatively affects the state of the whole organism.
Some of the cholesterol is ingested with food, and some is synthesized in the liver, adrenal glands, gonads and skin.
It also participates in the formation of cell membranes, the synthesis of hormones and other chemically active substances, and also participates in the metabolism of lipids in the human body. Indicators of cholesterol in the blood are often studied by doctors, as they show the state of lipid metabolism in the human body as a whole.
Lipids have their own special transport forms ─ lipoproteins. With their help, they can be carried with the blood stream without causing embolism.
Disorders of fat metabolism are most rapidly and clearly manifested by disorders of cholesterol metabolism, the predominance of atherogenic carriers (the so-called low and very low density lipoproteins) over antiatherogenic (high density lipoproteins).
The main manifestation of lipid metabolism pathology is the development of atherosclerosis.
It manifests itself as a narrowing of the lumen of arterial vessels throughout the body. Depending on the prevalence in the vessels of various localizations, a narrowing of the lumen of the coronary vessels develops (accompanied by angina pectoris), cerebral vessels (with impaired memory, hearing, possible headaches, noise in the head), renal vessels, vessels of the lower extremities, vessels of the digestive system with corresponding symptoms ...
Thus, lipids are at the same time an indispensable substrate for many processes in the body and, at the same time, when fat metabolism is disturbed, they can cause many diseases and pathological conditions. Therefore, fat metabolism requires control and correction when such a need arises.
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