Chemically, most lipids are esters of higher carboxylic acids and a number of alcohols. The best known among them are fats. Each fat molecule is formed by a molecule of a triatomic alcohol of glycerol and attached to it ether bonds of three molecules of higher carboxylic acids. According to the accepted nomenclature, fats are called triacylglcherols.
The carbon atoms in the molecules of higher carboxylic acids can be connected to each other by both single and double bonds. Of the limiting (saturated) higher carboxylic acids, palmitic, stearic, arachidic acids are most often included in the composition of fats; from unsaturated (unsaturated) - oleic and linoleic.
The degree of unsaturation and the chain length of higher carboxylic acids (i.e., the number of carbon atoms) determine the physical properties of a particular fat.
Fats with short and unsaturated acid chains have a low melting point. At room temperature, these are liquids (oils) or greasy substances (fats). Conversely, fats with long and saturated chains of higher carboxylic acids become solid at room temperature. That is why, during hydrogenation (saturation of acid chains with hydrogen atoms along double bonds), liquid peanut oil, for example, becomes buttery-like, and sunflower oil turns into solid margarine. Compared to inhabitants of southern latitudes, animals living in cold climates (for example, fish from the Arctic seas) usually contain more unsaturated triacylglycerols. For this reason, their body remains flexible even at low temperatures.
In phospholipids, one of the extreme chains of the higher carboxylic acids of triacylglycerol is replaced by a group containing phosphate. Phospholipids have polar heads and non-polar tails. The groups forming the polar head 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 is made up 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 of plants, as well as waxes).
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 fat is oxidized, a large amount of energy is released, which goes into the formation of ATP. A significant part of the body's energy reserves is stored in the form of lipids, which are consumed when there is a lack of nutrients. Hibernating animals and plants accumulate fats and oils and use them to maintain vital processes. The high content of lipids in plant seeds ensures the development of the embryo and seedling before their transition to independent feeding. The seeds of many plants (coconut palm, castor oil plant, sunflower, soybean, rapeseed, etc.) are used as raw materials for the production of vegetable oil industrially.
Protective and heat-insulating. Accumulating in the subcutaneous tissue and around some organs (kidneys, intestines), the fat layer protects the animal body and its individual organs from mechanical damage. In addition, due to its low thermal conductivity, the layer of subcutaneous fat helps to retain heat, which allows, for example, many animals to live in cold climates. In whales, in addition, it plays another role - it contributes to buoyancy.
Lubricating and water repellent. The wax covers the skin, wool, feathers, makes them more elastic and protects them from moisture. 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). Derivatives of cholesterol, 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 the source of metabolic water formation. Oxidation of 100 g of fat gives about 105 g of water. This water is very important for some desert inhabitants, in particular for camels, which can go without water for 10-12 days: the fat stored in the hump is used for this very purpose. Bears, marmots and other hibernating animals receive the water necessary 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.
The wax is used by bees to build honeycombs.
Lipids (Fats).Lipids- called a complex mixture of organic compounds (compounds with carbon C), with similar physical and chemical properties:
- insolubility in water.
- good solubility in organic solvents (gasoline, chloroform)Lipids are widespread in nature. Together with proteins and carbohydrates, they constitute the bulk of the organic matter of all living organisms, being an indispensable component of every cell. Lipids - the most important component of food, largely determines its nutritional value and taste.
In plants, they accumulate mainly in seeds and fruits. In animals and fish, lipids are concentrated in the subcutaneous fatty tissues, in the abdominal cavity and tissues surrounding many important organs (heart, kidneys), as well as in the brain and nervous tissues. There are especially many lipids in the subcutaneous adipose tissue of whales (25-30% of their mass), seals and other marine animals. In humans, the lipid content ranges from 10-20% on average.Types of lipids.
There are many types of fat classifications, we will analyze the simplest one, it divides them into three large groups:
- Simple lipids
- Complex lipids
- Derivatives of lipids.Let's analyze each group of lipids separately, what they include, and what they are for.
Simple Lipids.
1) Neutral fats (or just fats).
Neutral fats are made up of triglycerides.
Triglyceride - lipid or neutral fat, which contains glycerin combined with three fatty acid molecules.
Glycerol- chemical compound with the formula C3H5 (OH) 3, (colorless, viscous, odorless sweetish liquid.)
Fatty acid– natural or created compounds with one or more groups - COOH (carboxyl) that do not create cyclic bonds (aromatic), with the number of carbon atoms (C) in the chain at least 6.Triglycerides are produced from the breakdown of dietary fats and are a form of fat storage in the human body. The majority of dietary fats (98%) are triglycerides. Fat is also stored in the body as triglycerides.
Types of fatty acids:
- Saturated fatty acids- contain only single bonds between carbon atoms with all other bonds attached to hydrogen atoms. The molecule combines with the maximum possible number of hydrogen atoms, therefore this acid is called saturated. They differ from unsaturated ones in that they remain solid at room temperature.
Foods that contain the most saturated fat are lard and fat, chicken, beef and lamb fat, butter and margarine. Foods rich in such fats include sausage, small sausages and other sausages, bacon, ordinary lean beef; varieties of meat called "marble"; chicken skin, bacon; ice cream, creams, cheeses; most of the flour and other confectionery products.- unsaturated fatty acids - contain one or more double bonds along the main carbon chain. Each double bond reduces the number of hydrogen atoms that can bind to the fatty acid. Double bonds also cause a "bend" in fatty acids, which prevents bonding between them.
Unsaturated fatty acids are found in plant sources.They can be divided into two types:
1) monounsaturated - unsaturated fatty acids with one double bond. (e.g. olive oil)
2) polyunsaturated - unsaturated fatty acids with two or more double bonds. (for example - linseed oil)There will be a separate big topic about edible fats, which examines in detail all their properties.
2) Waxes.
Waxes are fat-like substances of animal or vegetable origin, consisting of esters of monohydric alcohols and fatty acids.
Esters– compounds - COOH (carboxyl), in which the hydrogen atom in the HO group is replaced by an organic group.
Alcohols– –OH compounds bonded to the carbon atom.
In simple words, waxes are shapeless, plastic, easily softened when heated, melting in the temperature range from 40 to 90 degrees Celsius.
Beeswax is secreted by special glands of honey bees, from which bees build honeycombs.Complex lipids.
A complex lipid is a triglyceride that combines with other chemicals.
There are three types of them.Phospholipids- glycerin combined with one or two fatty acids as well as phosphoric acid.
The cell membrane is composed of phospholipids. The most popular in food products is lecithin.Glycolipids - compounds of fat and carbohydrate components. (Contained in all tissues, mainly in the outer lipid layer of plasma membranes.)
Lipoproteins- complexes of fats and proteins. (Blood plasma)
Derivatives of lipids.
Cholesterol is a wax-like fatty substance found in every cell of the body and in many foods. Some blood cholesterol is needed, but high levels can lead to heart disease.
A lot of cholesterol is found in eggs, fatty meats, sausages, fatty dairy products.With the general classification figured out, what functions do lipids perform?
Functions.
- Structural function.
Phospholipids are involved in the construction of cell membranes in all organs and tissues. They are involved in the formation of many biologically important compounds.
- Energy function.
When fat is oxidized, a large amount of energy is released, which goes into the formation of ATP. A significant part of the body's energy reserves is stored in the form of lipids, which are consumed when there is a lack of nutrients. Hibernating animals and plants accumulate fats and oils and use them to maintain vital processes. The high content of lipids in plant seeds ensures the development of the embryo and seedling before their transition to independent feeding. The seeds of many plants (coconut, castor bean, sunflower, soybeans, rapeseed, etc.) are used as raw materials for the production of vegetable oil in an industrial way .. With complete decomposition of 1 g of fat, 38.9 kJ of energy is released, which is about 2 times more carbohydrates and proteins.
- Protective and heat-insulating
Accumulating in the subcutaneous tissue and around some organs (kidneys, intestines), the fat layer protects the animal body and its individual organs from mechanical damage. In addition, due to its low thermal conductivity, the layer of subcutaneous fat helps to retain heat, which allows, for example, many animals to live in cold climates.
Lubricating and water repellent.
The wax covers the skin, wool, feathers, makes them more elastic and protects them from moisture. Leaves and fruits of many plants have a waxy coating.- Regulatory.
Many hormones are derived from cholesterol, such as sex hormones (testosterone at men and progesterone in women) and corticosteroids. Derivatives of cholesterol, vitamin D play a key role in the metabolism of calcium and phosphorus. Bile acids are involved in digestion processes. In the myelinated (non-conductive charge) sheaths of the axons of nerve cells, lipids are insulators during the conduction of nerve impulses.
- Source of metabolic water.
Oxidation of 100 g of fat gives approximately 105-107 g of water. This water is very important for some desert inhabitants, in particular for camels, which can go without water for 10-12 days: the fat stored in the hump is used for this very purpose. Bears, marmots and other hibernating animals receive the water necessary for life as a result of fat oxidation.
Lipids - what are they? Translated from Greek, the word "lipids" means "small particles of fat". They are groups of natural organic compounds of an extensive nature, including fats themselves, as well as fat-like substances. They are part of all living cells without exception and are divided into simple and complex categories. The composition of simple lipids includes alcohol and fatty acids, while complex lipids contain high molecular weight components. Both are associated with biological membranes, have an effect on active enzymes, and also participate in the formation of nerve impulses that stimulate muscle contractions.
Fats and hydrophobia
One of them is the creation of the body's energy reserve and the provision of the water-repellent properties of the skin, coupled with thermal insulation protection. Some fatty acid-free substances are also classified as lipids, such as terpenes. Lipids are not susceptible to the action of the aquatic environment, but they easily dissolve in organic liquids such as chloroform, benzene, acetone.
Lipids, which are periodically presented at international seminars in connection with new discoveries, are an inexhaustible topic for research and scientific research. The question "Lipids - what are they?" never loses its relevance. However, scientific progress does not stand still. Recently, several new fatty acids have been identified that are biosynthetically related to lipids. The classification of organic compounds can be difficult due to the similarity in certain characteristics, but with a significant difference in other parameters. Most often, a separate group is created, after which the general picture of the harmonious interaction of related substances is restored.
Cell membranes
Lipids - what is it in terms of functional purpose? First of all, they are the most important component of living cells and tissues of vertebrates. Most of the processes in the body occur with the participation of lipids, the formation of cell membranes, interconnection and exchange of signals in the intercellular environment are not complete without fatty acids.
Lipids - what are they when viewed from the perspective of spontaneously emerging steroid hormones, phosphoinositides and prostaglandins? This is, first of all, the presence in blood plasma, which, by definition, are separate components of lipid structures. Because of the latter, the body is forced to develop the most complex systems for their transportation. Fatty acids of lipids are mainly transported in a complex with albumin, while lipoproteins, soluble in water, are transported in the usual manner.
Lipid classification
The categorization of biological compounds is a process that has some controversial issues. Lipids, due to their biochemical and structural properties, can be equally assigned to different categories. The main classes of lipids include simple and complex compounds.
Simple ones include:
- Glycerides are esters of glycerol alcohol and fatty acids of the highest category.
- Waxes are an ester of a higher fatty acid and a 2-atom alcohol.
Complex lipids:
- Phospholipid compounds - with the inclusion of nitrogenous components, glycerophospholipids, ophingolipids.
- Glycolipids are located in the outer biological layers of the body.
- Steroids are highly active substances of the animal spectrum.
- Complex fats - sterols, lipoproteins, sulfolipids, aminolipids, glycerol, hydrocarbons.
Functioning
Lipid fats act as a material for cell membranes. Participate in the transport of various substances along the periphery of the body. Fatty layers based on lipid structures help protect the body from hypothermia. They have the function of energy storage "in reserve".
Fat reserves are concentrated in the cytoplasm of cells in the form of droplets. Vertebrates, including humans, have special cells - adipocytes, which are capable of containing a lot of fat. The placement of fat accumulations in adipocytes is due to lipoid enzymes.
Biological functions
Fat is not only a reliable source of energy, it also has thermal insulating properties, aided by biology. At the same time, lipids allow achieving several useful functions, such as natural cooling of the body or, conversely, its thermal insulation. In the northern regions, characterized by low temperatures, all animals accumulate fat, which is deposited evenly throughout the body, and thus a natural protective layer is created that performs the function of heat protection. This is especially important for large marine animals: whales, walruses, seals.
Animals living in hot countries also accumulate fat deposits, but they are not distributed throughout the body, but are concentrated in certain places. For example, in camels, fat is collected in humps, in desert animals - in thick, short tails. Nature carefully monitors the correct placement of both fat and water in living organisms.
Structural function of lipids
All processes associated with the vital activity of the organism are subject to certain laws. Phospholipids are the basis of the biological layer of cell membranes, and cholesterol regulates the fluidity of these membranes. Thus, most living cells are surrounded by plasma membranes with a double layer of lipids. This concentration is essential for normal cellular activity. One microparticle of a biomembrane contains more than a million lipid molecules that have dual characteristics: they are simultaneously hydrophobic and hydrophilic. As a rule, these mutually exclusive properties are of a non-equilibrium nature, and therefore their functional purpose looks quite logical. Cell lipids are an effective natural regulator. The hydrophobic layer usually dominates and protects the cell membrane from the penetration of harmful ions.
Glycerophospholipids, phosphatidylethanolamine, phosphatidylcholine, cholesterol also contribute to cell impermeability. Other membrane lipids are located in tissue structures, these are sphingomyelin and sphingoglycolipid. Each substance has a specific function.
Lipids in the human diet
Triglycerides - nature, are an effective source of energy. acids are found in meat and dairy products. And fatty acids, but unsaturated, are found in nuts, sunflower and olive oil, seeds and corn grains. To prevent an increase in cholesterol levels in the body, it is recommended to limit the daily intake of animal fats to 10 percent.
Lipids and carbohydrates
Many organisms of animal origin "store" fats at certain points, subcutaneous tissue, in the folds of the skin, and in other places. The oxidation of lipids of such fat deposits is slow, and therefore the process of their transition to carbon dioxide and water allows you to get a significant amount of energy, almost twice as much as carbohydrates can provide. In addition, the hydrophobic properties of fats eliminate the need for large amounts of water to stimulate hydration. The transition of fats to the energy phase occurs "dry". However, fats act much more slowly in terms of energy release and are more suitable for hibernating animals. Lipids and carbohydrates, as it were, complement each other in the process of the body's vital activity.
Fat is considered to be the culprit of many troubles. Doctors and scientists advise cutting down on fat or eliminating it altogether. Of course, those who are obese or have chronic diseases are better off taking this advice. However, the rest would be foolish to give up fat. Let's find out more about them from the facts below.
1. Consumption of fats does not necessarily lead to their storage in the body
Many people think that fat consumption will definitely affect the figure in the form of deposits on the waist, hips and abdomen. If you eat more than your body requires, then yes, such a problem may arise. For example, if you consume an unlimited amount of starchy carbohydrates, then you can expect an increase in insulin levels, and then fat will be deposited. But if you eat, consuming fat and protein evenly, then this problem can be avoided. In everything you need to know when to stop.
2. No need to avoid the consumption of nuts
Nuts contain healthy forms of fat, monounsaturated fats, which help you feel full faster, but also raise your good cholesterol. Nuts do not affect weight gain in any way, because you cannot eat a lot of them due to their satiety, and besides, they are poorly digested by the body. Consequently, the cell walls of nuts are not easily destroyed when chewed. This means that they pass through the body in transit and do not excrete all of their fat.
3. It is not necessary to completely eliminate saturated fat from the body.
Saturated fats have always been thought to be the enemy of health, so they were advised to be eliminated from the diet. But today it has become clear that moderate consumption of saturated fat does no harm. And some of them even need to be included in a healthy eating program.
Extra virgin coconut oil is one of the healthy sources of saturated fat. It contains lauric acid which is found nowhere else except in breast milk. It is a powerful immune stimulant. It is advised to fry food in coconut oil.
4. If the product label says "no trans fats" does not mean that they are not there.
Many manufacturers believe that if a product contains a very small amount of an ingredient, then it is not necessary to indicate it on the label. It happens that a product contains only 0.5 g of trans fat, but you will not find it among the ingredients on the package. After eating several servings of such a product, you will not even know that you have eaten enough of this harmful ingredient.
5. Nutrients from vegetables without fat are absorbed worse
Studies have shown that lettuce seasoned with fat or a sauce with fats is significantly better absorbed by the body and receives more of the necessary nutrients - carotenoids. If you constantly eat salads without fats, then carotenoids will not be absorbed by the body at all. They are responsible for the colors red, yellow, orange and green and are important in the prevention of many diseases. To help your body absorb all the nutrients from vegetables, consume them with healthy fats.
6. Extra virgin olive oil is not suitable for frying.
Although it contains healthy monounsaturated fats, it loses its properties at high temperatures. Better to use it for dressing salads or marinating meat. Olive oil is very delicate and quickly deteriorates, so it should be stored in a dark glass container with a tightly closed lid to avoid oxidation and retain all its beneficial properties.
7. Fats have many functions in the body
Our body and our body cannot live without fats. There are several reasons for this:
The brain needs fats. About 60% of the dry weight of the human brain is fat. Healthy nerve cells contain fats - docosahexanoic acid;
Sex hormones are formed with the help of fats;
Fatty acids are essential for healthy skin and hair;
Fats are involved in metabolism, functions of the immune system, and help stabilize blood sugar.
Lipids (from the Greek. lipos- fat) include fats and fat-like substances. Contained in almost all cells - from 3 to 15%, and in the cells of subcutaneous fatty tissue up to 50%.
There are especially many lipids in the liver, kidneys, nervous tissue (up to 25%), blood, seeds and fruits of some plants (29-57%). Lipids have different structures, but some common properties. These organic substances do not dissolve in water, but they dissolve well in organic solvents: ether, benzene, gasoline, chloroform, etc. This property is due to the fact that non-polar and hydrophobic structures prevail in lipid molecules. All lipids can be roughly divided into fats and lipoids.
Fats
The most common are fats(neutral fats, triglycerides), which are complex compounds of a trihydric alcohol of glycerol and high molecular weight fatty acids. The remainder of glycerin is a substance that is highly soluble in water. Fatty acid residues are hydrocarbon chains that are almost insoluble in water. When a drop of fat enters the water, the glycerol part of the molecules turns to it, and the chains of fatty acids protrude from the water. The fatty acids contain a carboxyl group (-COOH). It ionizes easily. With its help, fatty acid molecules combine with other molecules.
All fatty acids are divided into two groups - saturated and unsaturated ... Unsaturated fatty acids do not have double (unsaturated) bonds, saturated ones do. Saturated fatty acids include palmitic, butyric, lauric, stearic, etc. Unsaturated - oleic, erucic, linoleic, linolenic, etc. The properties of fats are determined by the qualitative composition of fatty acids and their quantitative ratio.
Fats that contain saturated fatty acids have a high melting point. They are generally hard in consistency. These are the fats of many animals, coconut oil. Fats that contain unsaturated fatty acids have a low melting point. These fats are predominantly liquid. Vegetable fats of a liquid consistency are bursting oils ... These fats include fish oil, sunflower, cotton, linseed, hemp oils, etc.
Lipoids
Lipoids can form complex complexes with proteins, carbohydrates and other substances. The following compounds can be distinguished:
- Phospholipids. They are complex compounds of glycerol and fatty acids and contain a phosphoric acid residue. All phospholipid molecules have a polar head and a non-polar tail formed by two fatty acid molecules. The main components of cell membranes.
- Waxes. These are complex lipids, composed of more complex alcohols than glycerol and fatty acids. They have a protective function. Animals and plants use them as water-repellent and drying-out agents. Waxes cover the surface of plant leaves, the surface of the body of arthropods living on land. Waxes secrete the sebaceous glands of mammals, the coccygeal gland of birds. Bees build honeycombs from wax.
- Steroids (from the Greek stereos - hard). These lipids are characterized by the presence of not carbohydrate, but more complex structures. Steroids include important substances in the body: vitamin D, hormones of the adrenal cortex, gonads, bile acids, cholesterol.
- Lipoproteins and glycolipids. Lipoproteins consist of proteins and lipids, glucoproteins - of lipids and carbohydrates. There are many glycolipids in the composition of brain tissues and nerve fibers. Lipoproteins are part of many cellular structures, provide their strength and stability.
Lipid functions
Fats are the main type storing substances. They are stored in semen, subcutaneous fatty tissue, adipose tissue, and the fatty body of insects. Fat stores significantly exceed carbohydrate stores.
Structural. Lipids are part of the cell membranes of all cells. The ordered arrangement of hydrophilic and hydrophobic ends of molecules is of great importance for the selective permeability of membranes.
Energy. Provide 25-30% of all energy required by the body. With the breakdown of 1 g of fat, 38.9 kJ of energy is released. This is almost twice as much compared to carbohydrates and proteins. In migratory birds and hibernating animals, lipids are the only source of energy.
Protective. A layer of fat protects delicate internal organs from shock, shock, damage.
Thermal insulation. Fats do not conduct heat well. Under the skin of some animals (especially marine animals), they are deposited and form layers. For example, a whale has a layer of subcutaneous fat of about 1 m, which allows it to live in cold water.
Many mammals have a special adipose tissue called brown fat. It has this color because it is rich in red-brown mitochondria, since they contain iron-containing proteins. This tissue generates heat energy, which is necessary for animals in low
temperatures. Brown fat surrounds vital organs (heart, brain, etc.) or lies in the path of blood that flows to them, and, thus, directs heat to them.
Endogenous water suppliers
When 100 g of fat is oxidized, 107 ml of water is released. Thanks to this water, there are many desert animals: camels, jerboas, etc. Animals during hibernation also produce endogenous water from fats.
A fatty substance covers the surface of the leaves, prevents them from getting wet during rains.
Some lipids have high biological activity: a number of vitamins (A, D, etc.), some hormones (estradiol, testosterone), prostaglandins.
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