07.04.2009
Fats make up approximately 44 percent of the diet. Recommendations about proper diet It is advised that this figure should not exceed 30 percent of total calories, and 25 percent would be even better.
Your fat intake should lean towards polyunsaturated and monounsaturated fats with maximum number saturated fat no more than 10 percent or less of that total 25 percent fat.
* To reduce the fat content when preparing an omelet, remove the yolk of every second egg, this will reduce fat and cholesterol levels, and you will not even feel the difference.
*Cottonseed oil is 25 percent saturated fat and is not the best to use.
* Soybean oil changes taste when long-term storage, due to changes in the levels of linolenic acid it contains.
* Sixty-four percent of the calories from caviar come from fat.
*Butter absorbs refrigerator odors, so it should be stored in a closed container.
* Butter can be stored in the refrigerator for only two weeks. If you need to save it for more long time, store in the freezer.
*Eight ounces of potato chips equals consuming 12 to 20 teaspoons of fat.
*Try using water instead of fat in some recipes. It is true that fats make dressings, etc., the taste becomes smooth, but if you mix water with flour, with corn starch (corn meal) or potato starch, it will save you from extra calories.
* Oils should be stored in dark containers and stored in a dark, cool place to reduce the risk of rancidity.
* When carob is made into candy, fat is added for texture, making the fat level close to that of real chocolate. In fact, the cocoa butter used in chocolate production is 60 percent saturated fat, while the fat in carob candies is, in most cases, 85 percent saturated fat.
*Using non-stick cookware and vegetable oil sprays will reduce fat consumption.
* Never eat mayonnaise-based salad dressing or salad unless you are sure it has been refrigerated until you are ready to eat it. Neglecting this is the culprit in thousands of cases. food poisoning, annually.
* Fish-related oils are more beneficial than meat-related oils. Fish contains a high percentage of omega fatty acids.
* Any margarine containing coconut or Palm oil will have a very high level saturated fat content. Labels now call them tropical oils (tropical plant oils).
* New fat substitutes continue to appear in our products. Don't forget that they are still synthetic and not natural product. They should not be seen as a panacea for replacing fat in our diet.
*Best butter Made from AA grade sweet cream.
*An ounce of sunflower seeds contains 160 calories and is not considered a dietary snack.
* A burrito topped with sour cream and guacamole (a sauce made from mashed avacado, tomatoes, spices and mayonnaise) can contain up to 1,000 calories and 59 percent fat.
* Research has shown that stearic acid, a saturated fat, has little effect on raising cholesterol levels.
*The new reduced-fat peanut butter has the same number of calories per serving as regular peanut butter, approximately 190 calories per serving, and has been added with sweeteners instead of fat.
* When you store some oils in the refrigerator, they may become cloudy (not clear, light cloudy), this is due to the formation of harmless crystals. Manufacturers sometimes refrigerate oils before releasing them for sale and remove these crystals in a process called “winterizing.” Now these oils will remain clear when cooled.
* Pork fat has large crystals, whereas butter small size. This is highly dependent on the texture of the fat and can be controlled during processing. The size of the crystals can be changed by shaking (shaking) the oil while it cools.
* Studies have shown that people on a diet miss fat more than sweets.
* People on a high-fat diet are more likely to get colon cancer, prostate cancer or breast cancer. Future research may show that this also has an effect harmful effect on the immune system.
Material "gala.net"
COMMENTS ON THIS NEWS. TOTAL: (0)
Therapeutic nutrition for diabetes!
Proper nutrition for diabetes mellitus plays a vital role, since diabetes mellitus is a disease associated with metabolic disorders. To put it very briefly and simply, in diabetes mellitus as a result of a violation normal functioning The pancreas decreases the production of insulin, the hormone responsible for the absorption of sugar by the body...
Thermal water for beauty
Almost every SPA center offers thermal showers. Thermal water, rich in mineral salts. The skin is not only moisturized, but also saturated with microelements.
| 23.09.2015 |
What are lipids, what is the classification of lipids, what is their structure and function? The answer to this and many other questions is given by biochemistry, which studies these and other substances that have great importance for metabolism.
What it is
Lipids are organic substances that are insoluble in water. The functions of lipids in the human body are diverse.
Lipids - this word means "small particles of fat"
This is first of all:
- Energy. Lipids serve as a substrate for storing and using energy. When 1 gram of fat is broken down, approximately 2 times more energy is released than when protein or carbohydrates of the same weight are broken down.
- Structural function. The structure of lipids determines the structure of the membranes of the cells of our body. They are arranged in such a way that the hydrophilic part of the molecule is located inside the cell, and the hydrophobic part is on its surface. Thanks to these properties of lipids, each cell, on the one hand, is autonomous system, fenced off from the outside world, and on the other hand, each cell can exchange molecules with others and with environment using special transport systems.
- Protective. The surface layer that we have on our skin and serves as a kind of barrier between us and the outside world is also made up of lipids. In addition, they, as part of adipose tissue, provide 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 their structural features. They have dual properties, since they have a soluble and insoluble part in the molecule.
Entry into the body
Lipids partly enter the human body with food, and partly can be synthesized endogenously. Splitting the main part dietary lipids occurs in the duodenum under the influence of pancreatic juice secreted by the pancreas and bile acids in the composition of bile. Having broken down, they are resynthesized again in the intestinal wall and, already as part of special transport particles ─ lipoproteins, ─ are ready to enter the lymphatic system and general blood flow.
A person needs to receive about 50-100 grams of fat from food every day, which depends on the condition of the body and the level of physical activity.
Classification
Classification of lipids depending on their ability to form soaps certain conditions divides them into the following classes of lipids:
- Saponifiable. This is the name for substances that, in an environment with alkaline reaction form salts of carboxylic acids (soaps). This group includes simple lipids and complex lipids. Both simple and complex lipids are important for the body; they have different structure and, accordingly, lipids perform different functions.
- Unsaponifiable. In an alkaline environment they do not form salts carboxylic acids. Biological chemistry includes fatty acid, 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 carbon-carbon double bonds). Examples of the first: stearic, palmitic. Examples of unsaturated and polyunsaturated fatty acids: oleic, linoleic, etc.
It is unsaturated fatty acids that are especially important for us and must be supplied with food.
Why? Because they:
- They serve as a component for the synthesis of cell membranes and participate in the formation of many biologically active molecules.
- Help maintain normal functioning of the endocrine and reproductive systems.
- 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: important mediators internal regulation, like eicosanoids. They have a unique (like almost everything in biology) chemical structure and, accordingly, unique Chemical properties. The main basis Arachidonic acid, which is one of the most important unsaturated fatty acids, is used for the synthesis of eicosanoids. It is eicosanoids that are responsible for the course of inflammatory processes in the body.
Their role in inflammation can be briefly described as follows:
- They change the permeability of the vascular wall (namely, they increase its permeability).
- Stimulate the release of leukocytes and other cells immune system in fabric.
- By using chemical substances 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 current situation, eicosanoids can dilate blood vessels, relax smooth muscles, reduce aggregation or, if necessary, cause the opposite effects: vasoconstriction, contraction of smooth muscles. muscle cells and thrombus formation.
Eicosanoids are a large group of physiologically and pharmacologically active compounds.
Studies have been conducted that show that people sufficient quantity those who received the main substrate for the synthesis of eicosanoids ─ arachidonic acid ─ with food (found in fish oil, fish, vegetable oils) suffered less from diseases of cardio-vascular system. Most likely, this is due to the fact that such people have a more advanced eicosanoid metabolism.
Substances of 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:
- They 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, necessary for the normal transmission of nerve impulses.
- They are one of the important components surfactant ─ a substance that ensures breathing processes, namely preventing the collapse of the alveoli during exhalation.
- Many of them play the role of receptors on the surface of cells.
- The significance of some complex fats secreted from cerebrospinal fluid, nervous tissue, cardiac muscle is not fully understood.
The simplest representatives of lipids in this group include phospholipids, glyco- and sphingolipids.
Cholesterol
Cholesterol is a substance of lipid nature with the most important value in medicine, since disruption of its metabolism negatively affects the condition of the entire organism.
Some of the cholesterol is ingested with food, and some is synthesized in the liver, adrenal glands, gonads and skin.
It is also involved in the formation of cell membranes, the synthesis of hormones and other chemicals. active substances, and also participates in lipid metabolism in the human body. Indicators of cholesterol in the blood are often examined 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 transported through the bloodstream without causing embolism.
Violations fat metabolism They are most quickly and clearly manifested by disorders of cholesterol metabolism, the predominance of atherogenic carriers (the so-called low- and very low-density lipoproteins) over anti-atherogenic ones (high-density lipoproteins).
The main manifestation of the pathology of lipid metabolism is the development of atherosclerosis.
It manifests itself by narrowing the lumen of arterial vessels throughout the body. Depending on the predominance in blood vessels various localizations narrowing of the lumen develops coronary vessels(accompanied by angina), cerebral vessels (with impaired memory, hearing, possible headaches, noise in the head), kidney vessels, blood vessels lower limbs, vessels of the digestive organs with corresponding symptoms.
Thus, lipids are at the same time an indispensable substrate for many processes in the body and, at the same time, if lipid metabolism is disturbed, they can cause many diseases and pathological conditions. Therefore, fat metabolism requires monitoring and correction when the need arises.
Lipids constitute a large and rather chemically heterogeneous group of constituents of living cells. organic matter, soluble in low-polar organic solvents (ether, benzene, chloroform, etc.) and insoluble in water. IN general view they are considered to be derivatives of fatty acids.
A peculiarity of the structure of lipids is the presence in their molecules of both polar (hydrophilic) and non-polar (hydrophobic) structural fragments, which gives lipids an affinity for both water and the non-aqueous phase. Lipids are biphilic substances, which allows them to carry out their functions at the interface.
10.1. Classification
Lipids are divided into simple(two-component), if the products of their hydrolysis are alcohols and carboxylic acids, and complex(multicomponent), when as a result of their hydrolysis, other substances are also formed, for example phosphoric acid and carbohydrates. Simple lipids include waxes, fats and oils, as well as ceramides; complex lipids include phospholipids, sphingolipids and glycolipids (Scheme 10.1).
Scheme 10.1.General classification of lipids
10.2. Structural components of lipids
All groups of lipids have two obligatory structural components - higher carboxylic acids and alcohols.
Higher fatty acids (HFAs). Many higher carboxylic acids were first isolated from fats, which is why they are called fatty. Biologically important fatty acids can be saturated(Table 10.1) and unsaturated(Table 10.2). Their general structural features:
They are monocarbon;
Include an even number of carbon atoms in the chain;
Have a cis configuration of double bonds (if present).
Table 10.1.Essential saturated fatty acid lipids
In natural acids, the number of carbon atoms ranges from 4 to 22, but acids with 16 or 18 carbon atoms are more common. Unsaturated acids contain one or more double bonds in the cis configuration. The double bond closest to the carboxyl group is usually located between the C-9 and C-10 atoms. If there are several double bonds, then they are separated from each other by the methylene group CH 2.
The IUPAC rules for DRCs allow the use of their trivial names (see Tables 10.1 and 10.2).
Currently, our own nomenclature of unsaturated liquid liquids is also used. In it, the terminal carbon atom, regardless of the length of the chain, is designated by the last letter Greek alphabetω (omega). The position of double bonds is counted not, as usual, from the carboxyl group, but from the methyl group. Thus, linolenic acid is designated as 18:3 ω-3 (omega-3).
Linoleic acid itself and unsaturated acids with a different number of carbon atoms, but with the arrangement of double bonds also at the third carbon atom, counting from the methyl group, constitute the omega-3 family of liquid fatty acids. Other types of acids form similar families of linoleic (omega-6) and oleic (omega-9) acids. For normal life For a person, the correct balance of lipids of three types of acids is of great importance: omega-3 ( linseed oil, fish fat), omega-6 (sunflower, corn oils) and omega-9 (olive oil) in the diet.
From saturated acids in lipids human body the most important are palmitic C16 and stearic C18 (see Table 10.1), and of the unsaturated ones - oleic C18:1, linoleic C18:2, linolenic and arachidonic C 20:4 (see Table 10.2).
It should be emphasized the role of polyunsaturated linoleic and linolenic acids as compounds irreplaceable for humans (“vitamin F”). They are not synthesized in the body and should be supplied with food in an amount of about 5 g per day. In nature, these acids are found mainly in vegetable oils. They contribute
Table 10 .2. Essential unsaturated fatty acid lipids
*Included for comparison. ** For cis isomers.
normalization lipid profile blood plasma. Linetol, a mixture ethyl ethers higher fatty unsaturated acids, is used as a lipid-lowering herbal medicine. Alcohols. Lipids may include:
Higher monohydric alcohols;
Polyhydric alcohols;
Amino alcohols.
In natural lipids, the most common are saturated and less often unsaturated long-chain alcohols (C 16 or more), mainly with an even number of carbon atoms. As an example of higher alcohols, cetyl CH 3 (CH 2 ) 15 OH and melissil CH 3 (CH 2) 29 OH alcohols that are part of waxes.
Polyhydric alcohols in most natural lipids are represented by the trihydric alcohol glycerol. Other polyhydric alcohols are found, such as the dihydric alcohols ethylene glycol and 1,2 propanediol, as well as myoinositol (see 7.2.2).
The most important amino alcohols that are part of natural lipids are 2-aminoethanol (colamine), choline, and serine and sphingosine, which also belong to the α-amino acids.
Sphingosine is an unsaturated long-chain dihydric amino alcohol. The double bond in sphingosine has trance-configuration, and the asymmetric atoms C-2 and C-3 - D-configuration.
Alcohols in lipids are acylated with higher carboxylic acids at the corresponding hydroxyl groups or amino groups. In glycerol and sphingosine, one of the alcohol hydroxyls can be esterified with a substituted phosphoric acid.
10.3. Simple lipids
10.3.1. Waxes
Waxes are esters of higher fatty acids and higher monohydric alcohols.
Waxes form a protective lubricant on the skin of humans and animals and protect plants from drying out. They are used in the pharmaceutical and perfume industries in the production of creams and ointments. An example is palmitic acid cetyl ester(cetin) - main component spermaceti. Spermaceti is secreted from the fat contained in the cavities of the skull of sperm whales. Another example is Palmitic acid melissil ester- component of beeswax.
10.3.2. Fats and oils
Fats and oils are the most common group of lipids. Most of them belong to triacylglycerols - complete esters of glycerol and IVG, although mono- and diacylglycerols are also found and take part in metabolism.
Fats and oils (triacylglycerols) are esters of glycerol and higher fatty acids.
In the human body, triacylglycerols play the role of a structural component of cells or a reserve substance (“fat depot”). Their energy value is approximately twice that of proteins
or carbohydrates. However increased level triacylglycerols in the blood is one of the additional risk factors for the development of coronary heart disease.
Solid triacylglycerols are called fats, liquid triacylglycerols are called oils. Simple triacylglycerols contain residues of the same acids, while mixed ones contain residues of different ones.
Triacylglycerols of animal origin usually contain predominantly saturated acid residues. Such triacylglycerols are usually solids. On the contrary, vegetable oils contain mainly residues of unsaturated acids and have a liquid consistency.
Below are examples of neutral triacylglycerols and their systematic and (in parentheses) commonly used trivial names, based on the names of their constituent fatty acids.
10.3.3. Ceramides
Ceramides are N-acylated derivatives of the alcohol sphingosine.
Ceramides are present in small quantities in the tissues of plants and animals. Much more often they are part of complex lipids- sphingomyelins, cerebrosides, gangliosides, etc.
(see 10.4).
10.4. Complex lipids
Some complex lipids are difficult to classify unambiguously, since they contain groups that allow them to be classified simultaneously into different groups. According to general classification Lipids (see Diagram 10.1) Complex lipids are usually divided into three large groups: phospholipids, sphingolipids and glycolipids.
10.4.1. Phospholipids
The group of phospholipids includes substances that remove phosphoric acid during hydrolysis, for example glycerophospholipids and some sphingolipids (Scheme 10.2). In general, phospholipids are characterized by a fairly high content of unsaturated acids.
Scheme 10.2.Classification of phospholipids
Glycerophospholipids. These compounds are the main lipid components of cell membranes.
By chemical structure glycerophospholipids are derivatives l -glycero-3-phosphate.
l-Glycero-3-phosphate contains an asymmetric carbon atom and, therefore, can exist in the form of two stereoisomers.
Natural glycerophospholipids have the same configuration, being derivatives of l-glycero-3-phosphate, formed during metabolism from dihydroxyacetone phosphate.
Phosphatides. Among glycerophospholipids, the most common are phosphatides - ester derivatives of l-phosphatidic acids.
Phosphatidic acids are derivatives l -glycero-3-phosphate, esterified with fatty acids at alcohol hydroxyl groups.
As a rule, in natural phosphatides, in position 1 of the glycerol chain there is a residue of a saturated acid, in position 2 - an unsaturated acid, and one of the hydroxyls of phosphoric acid is esterified with a polyhydric alcohol or amino alcohol (X is the residue of this alcohol). In the body (pH ~7.4), the remaining free hydroxyl of phosphoric acid and other ionic groups in phosphatides are ionized.
Examples of phosphatides are compounds containing phosphatidic acids esterified for phosphate hydroxyl with corresponding alcohols:
Phosphatidylserines, esterifying agent - serine;
Phosphatidylethanolamines, esterifying agent - 2-aminoethanol (in biochemical literature often, but not quite correctly, called ethanolamine);
Phosphatidylcholines, esterifying agent - choline.
These esterifying agents are related because the ethanolamine and choline moieties can be metabolized from the serine moiety by decarboxylation and subsequent methylation with S-adenosylmethionine (SAM) (see 9.2.1).
A number of phosphatides, instead of an amino-containing esterifying agent, contain residues of polyhydric alcohols - glycerol, myoinositol, etc. The phosphatidylglycerols and phosphatidylinositols given below as examples belong to acidic glycerophospholipids, since their structures do not contain fragments of amino alcohols, which give phosphatidylethanolamines and related compounds a neutral character.
Plasmalogens. Less common than ester glycerophospholipids are lipids with an ether linkage, in particular plasmalogens. They contain an unsaturated residue
* For convenience, the way of writing the configuration formula of the myoinositol residue in phosphatidylinositols has been changed from that given above (see 7.2.2).
alcohol linked by an ether bond to the C-1 atom of glycero-3-phosphate, such as plasmalogens with an ethanolamine fragment - L-phosphatidal ethanolamines. Plasmalogens make up up to 10% of all CNS lipids.
10.4.2. Sphingolipids
Sphingolipids are structural analogues of glycerophospholipids in which sphingosine is used instead of glycerol. Another example of sphingolipids is the ceramides discussed above (see 10.3.3).
An important group of sphingolipids are sphingomyelins, first discovered in nervous tissue. In sphingomyelins, the hydroxyl group of C-1 ceramide is esterified, as a rule, with choline phosphate (less often with colamine phosphate), so they can also be classified as phospholipids.
10.4.3. Glycolipids
As the name suggests, compounds of this group include carbohydrate residues (usually D-galactose, less often D-glucose) and do not contain a phosphoric acid residue. Typical representatives glycolipids - cerebrosides and gangliosides - are sphingosine-containing lipids (therefore they can be considered sphingolipids).
IN cerebrosides the ceramide residue is linked to D-galactose or D-glucose by a β-glycosidic bond. Cerebrosides (galactocerebrosides, glucocerebrosides) are part of the membranes of nerve cells.
Gangliosides- carbohydrate-rich complex lipids - were first isolated from the gray matter of the brain. Structurally, gangliosides are similar to cerebrosides, differing in that instead of a monosaccharide they contain a complex oligosaccharide, including at least one remainder V-acetylneuraminic acid (see Appendix 11-2).
10.5. Properties of lipids
and them structural components
A special feature of complex lipids is their biphilicity, caused by non-polar hydrophobic and highly polar ionized hydrophilic groups. In phosphatidylcholines, for example, the hydrocarbon radicals of fatty acids form two non-polar “tails”, and the carboxyl, phosphate and choline groups form the polar part.
At the interface, such compounds act as excellent emulsifiers. As part of cell membranes, lipid components provide high electrical resistance of the membrane, its impermeability to ions and polar molecules, and permeability to non-polar substances. In particular, most anesthetic drugs are highly lipid soluble, which allows them to penetrate the membranes of nerve cells.
Fatty acids are weak electrolytes( p K a~4.8). They're in small degree dissociated into aqueous solutions. At pH< p K a non-ionized form predominates, at pH > p Ka, i.e., under physiological conditions, the ionized form RCOO - predominates. Soluble salts of higher fatty acids are called soaps. Sodium salts of higher fatty acids are solid, potassium salts are liquid. As salts of weak acids and strong bases of soap are partially hydrolyzed in water, their solutions have an alkaline reaction.
Natural unsaturated fatty acids that have cis- double bond configuration, have a large supply of internal energy and, therefore, compared to trance-isomers are thermodynamically less stable. Their cis-trans -isomerization occurs easily when heated, especially in the presence of radical reaction initiators. IN laboratory conditions this transformation can be carried out by the action of nitrogen oxides formed during the decomposition of nitric acid when heated.
Higher fatty acids exhibit the general chemical properties of carboxylic acids. In particular, they easily form the corresponding functional derivatives. Fatty acids with double bonds exhibit the properties of unsaturated compounds - they add hydrogen, hydrogen halides and other reagents to the double bond.
10.5.1. Hydrolysis
Using the hydrolysis reaction, the structure of lipids is determined, and also obtained valuable products(soap). Hydrolysis is the first stage of utilization and metabolism of dietary fats in the body.
Hydrolysis of triacylglycerols is carried out either by exposure to superheated steam (in industry) or by heating with water in the presence of mineral acids or alkalis (saponification). In the body, lipid hydrolysis occurs under the action of lipase enzymes. Some examples of hydrolysis reactions are given below.
In plasmalogens, as in ordinary vinyl esters, the ether bond is cleaved in an acidic, but not in an alkaline, environment.
10.5.2. Addition reactions
Lipids containing unsaturated acid residues in their structure add hydrogen, halogens, hydrogen halides, and water through double bonds in an acidic environment. Iodine number is a measure of the unsaturation of triacylglycerols. It corresponds to the number of grams of iodine that can add to 100 g of a substance. The composition of natural fats and oils and their iodine numbers vary within fairly wide limits. As an example, we give the interaction of 1-oleoyl-distearoylglycerol with iodine (the iodine number of this triacylglycerol is 30).
Catalytic hydrogenation (hydrogenation) of unsaturated vegetable oils is an important industrial process. In this case, hydrogen saturates the double bonds and liquid oils turn into solid fats.
10.5.3. Oxidation reactions
Oxidative processes involving lipids and their structural components are quite diverse. In particular, the oxidation of unsaturated triacylglycerols by oxygen during storage (auto-oxidation, see 3.2.1), accompanied by hydrolysis, is part of the process known as rancidity of oil.
The primary products of the interaction of lipids with molecular oxygen are hydroperoxides formed as a result of a chain free radical process (see 3.2.1).
Lipid peroxidation - one of the most important oxidative processes in organism. It is the main cause of damage to cell membranes (for example, in radiation sickness).
Structural fragments of unsaturated higher fatty acids in phospholipids serve as targets for attack active forms of oxygen(AFC, see Appendix 03-1).
When attacked, in particular by the hydroxyl radical HO, the most active of ROS, the lipid molecule LH undergoes homolytic rupture S-N connections in the allylic position, as shown in the lipid peroxidation model (Scheme 10.3). The resulting allylic radical L" instantly reacts with molecular oxygen present in the oxidation environment to form the lipid peroxyl radical LOO". From this moment, a chain cascade of lipid peroxidation reactions begins, as continuing education allylic lipid radicals L", renewing this process.
Lipid peroxides LOOH are unstable compounds and can spontaneously or with the participation of metal ions of variable valence (see 3.2.1) decompose to form lipidoxyl radicals LO", capable of initiating further oxidation of the lipid substrate. Such an avalanche-like process of lipid peroxidation poses a danger of destruction of membrane structures cells.
The intermediately formed allylic radical has a mesomeric structure and can further undergo transformations in two directions (see diagram 10.3, paths A And b), leading to intermediate hydroperoxides. Hydroperoxides are unstable and even at ordinary temperatures decompose to form aldehydes, which are further oxidized into acids - the final products of the reaction. The result is general case two monocarboxylic and two dicarboxylic acids with shorter carbon chains.
Unsaturated acids and lipids with residues of unsaturated acids under mild conditions are oxidized with an aqueous solution of potassium permanganate, forming glycols, and in more rigid conditions (with the rupture of carbon-carbon bonds) - the corresponding acids.
Fat is considered the culprit of many ills. Doctors and scientists advise reducing fat intake or eliminating it from the diet altogether. Of course, for those who are obese or have chronic diseases, it is better to listen to this advice. However, the rest of us would be foolish to give up fat. Let's find out more about them with the facts below.
1. Consumption of fats does not necessarily lead to their deposition in the body.
Many people think that consuming fat will definitely affect their figure in the form of deposits on the waist, hips and abdomen. If you eat more than your body requires, then yes, this problem can arise. For example, if you consume starchy carbohydrates in unlimited quantities, you can expect an increase in insulin levels, and then fat will be deposited. But if you eat evenly consuming fats and proteins, then this problem can be avoided. In everything you need to know when to stop.
2. No need to avoid nuts
Nuts contain useful forms fats - monounsaturated fats, which help you feel full faster, but also increase healthy cholesterol. Nuts do not have any effect on weight gain, because you can’t 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 during chewing. This means that they pass through the body in transit and do not release all their fat.
3. There is no need to completely eliminate saturated fats from the body.
It has always been believed that saturated fats are the enemies of health, so they were advised to be excluded from the diet. But today it has become clear that moderate consumption of saturated fat does not cause any harm. And some of them even need to be included in a healthy eating program.
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 recommended to fry foods in coconut oil.
4. Just because a product label says “no trans fats” doesn’t mean they aren’t there.
Many manufacturers believe that if a product contains a very small amount of an ingredient, then there is no need to list 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 packaging. After eating several servings of this product, you will not even know that you have eaten enough of this harmful ingredient.
5. Nutrients from vegetables without fat are less absorbed
Studies have shown that salad seasoned with fat or sauce with fats is much better absorbed by the body and receives more of what it needs. nutrients- carotenoids. If you constantly eat salads without fat, then carotenoids will not be absorbed by the body at all. They are responsible for red, yellow, orange and green colors and are important for preventing many diseases. To ensure your body absorbs all the nutrients from vegetables, eat them with healthy fats.
6. Olive oil first spin not suitable for frying
Although it contains healthy monounsaturated fats, it high temperatures loses its properties. It is better to use it for dressing salads or marinating meat. Olive oil is very delicate and spoils quickly, so it should be stored in a dark glass container with a tightly closed lid to avoid oxidation and preserve all its beneficial properties.
7. Fats have many functions in the body.
Without fats, our body and our organism cannot live. Here are a few 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;
Sexual hormones are formed with the help of fats;
Fatty acids are essential for healthy skin and hair;
Fats are involved in metabolism, immune system functions, and help stabilize blood sugar.
Loading...