Chemically, most lipids are esters of higher carboxylic acids and a number of alcohols. The most famous among them are fats. Each fat molecule is formed by a molecule of the trihydric alcohol glycerol and ester bonds of three molecules of higher carboxylic acids attached to it. According to the accepted nomenclature, fats are called triacylglycerols.
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, most often in the composition of fats are palmitic, stearic, arachidic; from unsaturated (unsaturated) - oleic and linoleic.
The degree of unsaturation and the length of the chains 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's why hydrogenation (saturation of acid chains with hydrogen atoms in double bonds) liquid peanut butter, for example, becomes greasy, and sunflower oil turns into solid margarine. Compared with the inhabitants of the southern latitudes, the body of animals living in a cold climate (for example, fish in the Arctic seas) usually contains 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 are steroids (sterols). These substances are built on the basis of 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 (growth substances of plants - 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 fats are oxidized, a large amount of energy is released, which goes to the formation of ATP. In the form of lipids, a significant part of the body's energy reserves are stored, which are consumed when there is a lack of nutrients. Hibernating animals and plants accumulate fats and oils and use them to maintain life processes. The high content of lipids in plant seeds ensures the development of the embryo and seedling before their transition to independent nutrition. Seeds of many plants (coconut palm, castor bean, sunflower, soybean, rapeseed, etc.) serve as raw materials for industrial production of vegetable oil.
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. Wax coats the skin, wool, feathers, makes them more elastic and protects them from moisture. Leaves and fruits of many plants have a wax 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 exchange of calcium and phosphorus. Bile acids are involved in the processes of digestion (emulsification of fats) and absorption of higher carboxylic acids.
Lipids are also a source of metabolic water formation. Oxidation of 100 g of fat gives approximately 105 g of water. This water is very important for some desert dwellers, in particular for camels, who can go without water for 10-12 days: the fat stored in the hump is used for this purpose. Bears, marmots and other hibernating animals receive the water necessary for life as a result of fat oxidation.
In the myelin sheaths of axons of nerve cells, lipids are insulators during the conduction of nerve impulses.
Wax is used by bees in building honeycombs.
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lipids in nutrition
Along with proteins and carbohydrates, lipids are the main food elements that make up a significant part of food. The intake of lipids in the body with food has a significant impact on human health in general. Insufficient or excessive consumption of these substances can lead to the development of various pathologies. Most people eat a fairly varied diet, and all the necessary lipids enter their body. It should be noted that some of these substances are synthesized by the liver, which partly compensates for their lack in food. However, there are also essential lipids, or rather their components - polyunsaturated fatty acids. If they do not enter the body with food, over time this will inevitably lead to certain disorders.
Most of the lipids in food are used by the body to produce energy. That is why when fasting a person loses weight and weakens. Deprived of energy, the body begins to consume lipid reserves from subcutaneous adipose tissue.
Thus, lipids play a very important role in a healthy human diet. However, for certain diseases or disorders, their number should be strictly limited. Patients usually learn about this from the attending physician ( usually a gastroenterologist or nutritionist).
The energy value of lipids and their role in the diet
The energy value of any food is calculated in calories. A food product can be decomposed according to its composition into proteins, carbohydrates and lipids, which together make up the bulk. Each of these substances in the body breaks down with the release of a certain amount of energy. Proteins and carbohydrates are easier to digest, but the breakdown of 1 g of these substances releases about 4 Kcal ( kilocalories) energy. Fats are more difficult to digest, but the breakdown of 1 g releases about 9 kcal. Thus, the energy value of lipids is the highest.In terms of energy release, triglycerides play the largest role. Saturated acids, which are part of these substances, are absorbed by the body by 30 - 40%. Monounsaturated and polyunsaturated fatty acids are completely absorbed by a healthy body. Sufficient lipid intake allows carbohydrates and proteins to be used for other purposes.
Plant and animal lipids
All lipids that enter the body with food can be divided into substances of animal and vegetable origin. From a chemical point of view, the lipids that make up these two groups differ in their composition and structure. This is due to differences in the functioning of cells in plants and animals.Examples of plant and animal lipid sources
Each source of lipids has certain advantages and disadvantages. For example, animal fats contain cholesterol, which is not found in plant foods. In addition, animal products contain more lipids and are more beneficial from an energy point of view. At the same time, an excess of animal fats increases the risk of developing a number of diseases associated with lipid metabolism in the body ( atherosclerosis, cholelithiasis, etc.). There are fewer lipids in plant products, but the body cannot synthesize them on its own. Even a small amount of seafood, citrus fruits or nuts provides enough polyunsaturated fatty acids that are vital for a person. At the same time, a small proportion of lipids in plants cannot fully cover the energy costs of the body. That is why, to maintain health, it is recommended to make the diet as diverse as possible.
What is the daily requirement of the body for lipids?
Lipids are the body's main source of energy, but too much of them can be detrimental to health. First of all, this applies to saturated fatty acids, most of which are deposited in the body and often leads to obesity. The optimal solution is to maintain the necessary proportions between proteins, fats and carbohydrates. The body should receive the same number of calories that it spends during the day. That is why lipid intake rates can be different.The following factors can influence the body's need for lipids:
- Body weight. Overweight people have to expend more energy. If they are not going to lose weight, then the need for calories and, accordingly, lipids will be slightly higher. If they are trying to lose weight, then limit, in the first place, you need exactly fatty foods.
- Loads during the day. People doing heavy physical work or athletes need a lot of energy. If the average person has 1500 - 2500 calories, then for miners or loaders the norm can reach up to 4500 - 5000 calories per day. Of course, the need for lipids also increases.
- The nature of nutrition. Every country and every nation has its own food traditions. When calculating the optimal diet, one must take into account which foods a person usually consumes. In some nations, fatty foods are a kind of tradition, while others, on the contrary, are vegetarians, and their lipid intake is minimized.
- The presence of comorbidities. In a number of disorders, lipid intake should be limited. First of all, we are talking about diseases of the liver and gallbladder, since these organs are responsible for the digestion and absorption of lipids.
- The age of the person. In childhood, the metabolism is faster and the body requires more energy for normal growth and development. In addition, children usually do not have serious problems with the gastrointestinal tract, and they digest any food well. It should also be borne in mind that infants receive an optimal set of lipids from breast milk. Thus, age strongly influences the rate of fat intake.
- Floor. It is believed that on average a man consumes more energy than a woman, so the rate of fat in the diet of men is slightly higher. However, in pregnant women, the need for lipids increases.
It is difficult for a person to independently make the necessary calculations and take into account all the factors for choosing the optimal diet. To do this, it is better to consult a dietitian or food hygienist. After a short survey and clarification of the nature of nutrition, they will be able to draw up the optimal daily diet, which the patient will adhere to in the future. They can also recommend specific foods that contain essential lipids.
What foods contain the most lipids? milk, meat, etc.)?
Lipids are found in some amount in almost all foods. However, in general, animal products are richer in these substances. In plants, the mass fraction of lipids is minimal, but the fatty acids included in such lipids are most important for the body.The amount of lipids in a particular product is usually indicated on the packaging of the product in the "nutrition value" section. Most manufacturers are required to inform consumers about the mass fraction of proteins, carbohydrates and fats. In self-cooked food, the amount of lipids can be calculated using special tables for nutritionists, which list all the main foods and dishes.
Mass fraction of lipids in staple foods
In most plant products ( vegetables, fruits, herbs, root crops) mass fraction of fats is not more than 1 - 2%. The exceptions are citrus fruits, where the proportion of lipids is somewhat higher, and vegetable oils, which are a lipid concentrate.
Are there essential lipids, and what are their most important sources?
The structural unit of lipids are fatty acids. Most of these acids can be synthesized by the body ( mostly in liver cells) from other substances. However, there are a number of fatty acids that the body cannot produce on its own. Thus, lipids containing these acids are essential.Most of the essential lipids are found in foods of plant origin. These are monounsaturated and polyunsaturated fatty acids. The cells of the body cannot synthesize these compounds, since the metabolism of animals is very different from that of plants.
Essential fatty acids and their main dietary sources
For a long time, the above fatty acids were equal in importance to the body to vitamins. Sufficient consumption of these substances strengthens the immune system, accelerates cell regeneration, reduces inflammation, and promotes the conduction of nerve impulses.
What does a lack or excess of lipids in the diet lead to?
Both deficiency and excess of lipids in the diet can seriously affect the health of the body. In this case, we are not talking about a one-time intake of a large amount of fat ( although this may have some consequences.), but about the systematic abuse of fatty foods or prolonged fasting. At first, the body is quite capable of successfully adapting to a new diet. For example, with a lack of lipids in food, the most important substances for the body will still be synthesized by its own cells, and energy needs will be covered by the breakdown of fat reserves. With an excess of lipids in the diet, a significant part will not be absorbed in the intestines and will leave the body with fecal matter, and some of the lipids that enter the blood will be transformed into adipose tissue. However, these adaptation mechanisms are temporary. In addition, they work well only in a healthy body.Possible Consequences of Dietary Lipid Imbalance
Blood and plasma lipids
A significant part of lipids is present in the blood in various forms. Most often, these are compounds of lipids with other chemicals. For example, triglycerides and cholesterol are transported primarily as lipoproteins. The levels of various lipids in the blood can be determined using biochemical blood tests. This allows you to identify a number of violations and suspect the corresponding pathology. Triglycerides
Triglycerides perform mainly an energy function. They enter the body with food, are absorbed in the intestines and are carried throughout the body with the blood in the form of various compounds. The normal content is considered to be the level of 0.41 - 1.8 mmol / l, but it can fluctuate significantly. For example, after eating a large amount of fatty foods, the level of triglycerides in the blood can increase by 2 to 3 times.Free fatty acids
Free fatty acids enter the bloodstream as a result of the breakdown of triglycerides. Normally, they are deposited in adipose tissue. Modern studies have shown the relationship between the level of free fatty acids in the blood and some pathological processes. For example, in people with a high concentration of fatty acids ( on an empty stomach) insulin is produced worse, so the risk of developing diabetes is higher. The normal content of fatty acids in the blood of an adult is 0.28 - 0.89 mmol / l. In children, the limits of the norm are wider ( up to 1.10 mmol/l).Cholesterol
Cholesterol is one of the most important lipids in the human body. It is part of many cellular components and other substances, affecting a variety of processes. An excess or deficiency of this substance or a violation of its absorption by the body can lead to the development of serious diseases.Cholesterol performs the following functions in the human body:
- gives rigidity to cell membranes;
- takes part in the synthesis of steroid hormones;
- is part of bile;
- participates in the absorption of vitamin D;
- regulates the permeability of the walls of some cells.
Lipoproteins ( lipoproteins) and their fractions ( low density, high density, etc.)
The term lipoproteins or lipoproteins refers to a group of complex protein compounds that carry out the transport of lipids in the blood. Some lipoproteins are fixed in cell membranes and perform a number of functions related to cell metabolism.All blood lipoproteins are divided into several classes, each of which has its own characteristics. The main criterion by which lipoproteins are distinguished is their density. According to this indicator, all these substances are divided into 5 groups.
There are following classes ( factions) lipoproteins:
- high density. HDL) are involved in the transfer of lipids from body tissues to the liver. From a medical point of view, they are considered useful, because due to their small size they can pass through the walls of blood vessels and “cleanse” them of lipid deposits. Thus, a high level of HDL reduces the risk of atherosclerosis.
- Low density. LDL) transport cholesterol and other lipids from the liver ( places of their synthesis) to tissues. From a medical point of view, this fraction of lipoproteins is harmful, since it is LDL that contributes to the deposition of lipids on the walls of blood vessels with the formation of atherosclerotic plaques. High LDL levels greatly increase the risk of atherosclerosis.
- Medium ( intermediate) density. Intermediate density lipoproteins ( LPPP) have no significant diagnostic value, as they are an intermediate product of lipid metabolism in the liver. They also carry lipids from the liver to other tissues.
- Very low density. VLDL) transport lipids from the liver to tissues. They also increase the risk of atherosclerosis, but play a minor role in this process ( after LDL).
- Chylomicrons. Chylomicrons are much larger than other lipoproteins. They are formed in the walls of the small intestine and carry lipids from food to other organs and tissues. These substances do not play a significant role in the development of various pathological processes.
Lipid analysis
Currently, there are many laboratory tests that can determine various lipids in the blood. Usually venous blood is taken for this. The attending physician sends the patient for analysis. The most important lipids ( total cholesterol, triglycerides) is determined in a biochemical blood test. If the patient needs a more detailed examination, the doctor indicates which lipids need to be determined. The analysis itself usually takes several hours. Most labs provide results the next day. What is a lipid profile?
Lipidogram is a set of laboratory blood tests aimed at determining the level of lipids in the blood. This is the most useful study for patients with various lipid disorders, as well as for patients with atherosclerosis. Some indicators included in the lipid profile are also determined in a biochemical blood test, but in some cases this may not be enough to make an accurate diagnosis. The lipid profile is prescribed by the attending physician, based on the symptoms and complaints of the patient. This analysis is carried out by almost any biochemical laboratory.Lipidogram includes tests to determine the following blood lipids:
- Cholesterol. This indicator does not always depend on lifestyle and nutrition. A significant part of cholesterol in the blood is the so-called endogenous cholesterol, which is produced by the body itself.
- Triglycerides. Triglyceride levels usually rise or fall in proportion to cholesterol levels. It can also rise after eating.
- Low density lipoproteins ( LDL). The accumulation of these compounds in the blood greatly increases the risk of atherosclerosis.
- High density lipoproteins ( HDL). These compounds are able to "cleanse" the vessels from excess cholesterol and are beneficial to the body. A low HDL level indicates that the body is not absorbing fats well.
- Very low density lipoproteins ( VLDL). They are of secondary diagnostic value, but their increase, along with an increase in LDL levels, usually indicates atherosclerosis.
Before donating blood for a lipid profile, you should follow a few simple rules. They will help to avoid significant fluctuations in blood lipid levels and make the results more reliable.
Before testing, patients should consider the following recommendations:
- In the evening before the test, you can eat, but you should not abuse fatty foods. It is better to stick to the usual diet.
- The day before the test, it is necessary to exclude various kinds of loads ( both physical and emotional), as they can lead to the breakdown of adipose tissue stores in the body and an increase in blood lipid levels.
- In the morning, immediately before donating blood, you should not smoke.
- Regular intake of a number of drugs also affects the level of lipids in the blood ( contraceptives, hormonal drugs, etc.). It is not necessary to cancel them, but this fact must be taken into account when interpreting the results.
Normal blood lipid levels
The boundaries of the norm for all people are somewhat different. It depends on gender, age, the presence of chronic pathologies and a number of other indicators. However, there are certain limits, the excess of which clearly indicates the presence of problems. The table below shows the generally accepted limits of the norm for various blood lipids.The limits of the norm are relative, and the patient himself cannot always draw the right conclusions when interpreting the results of the analysis. When reviewing the results, the attending physician will definitely take into account that during pregnancy, the limits of the norm expand, as with fasting. Therefore, you should not panic with some deviations from the norm. In any case, the final conclusion should be made by the attending physician.
Diseases associated with lipid metabolism
There are quite a few diseases that are to some extent associated with the metabolism of lipids in the body. Some of these pathologies cause an increase or decrease in various lipids in the blood, which is reflected in the tests. Other pathologies are the result of lipid imbalance. lipid metabolism disorders ( dyslipidemia)
Excess or lack of lipids in the diet can lead to a variety of pathologies. In a healthy body, normally assimilating all incoming substances, this imbalance does not affect metabolic processes so much. For example, an excess of lipids does not always lead to obesity. For this, a person must also have a genetic predisposition, endocrine disorders, or he must lead a sedentary lifestyle. In other words, the amount of lipids in the diet in most cases is only one of many factors influencing the appearance of pathology.Lipid imbalance can lead to the following pathologies:
- atherosclerosis ( as a result - aneurysms, coronary heart disease, hypertension or other problems with the cardiovascular system);
- skin problems;
- problems with the nervous system;
- a number of pathologies of the gastrointestinal tract ( pancreatitis, cholelithiasis, etc.).
Causes of high and low lipid levels
The most common cause of elevated lipid levels in a blood test is a mistake made when donating blood. Patients do not donate blood on an empty stomach, which is why the lipid content does not have time to normalize, and the doctor may mistakenly suspect some problems. However, there are many pathologies that cause lipid disorders in the blood, regardless of nutrition.Pathological conditions associated with changes in the amount of lipids in the blood are called dyslipidemias. They are also divided into several types. If the level of triglycerides in the blood is elevated, they speak of hypertriglyceridemia ( synonym - hyperlipemia). If the level of cholesterol rises, they speak of hypercholesterolemia.
Also, all dyslipidemias by origin are divided into the following groups:
- Primary. Primary dyslipidemias are mainly genetic diseases and abnormalities. As a rule, they are manifested by an excess or deficiency of any enzymes, which disrupts lipid metabolism. As a result, the amount of these substances in the blood decreases or increases.
- Secondary. Secondary dyslipidemias are pathological conditions in which an increase in blood lipids is a consequence of some other pathology. Thus, it is necessary to treat, first of all, this particular pathology, then the lipid level will gradually stabilize.
There are five main types of primary hyperlipoproteinemias ( elevated lipoprotein levels):
- Hyperchylomicronemia. With this disease, the level of triglycerides in the blood rises, while the level of other lipids usually remains within the normal range. Patients may experience paroxysmal abdominal pain, but without tension in the abdominal muscles. Xanthomas may appear on the skin ( brown or yellowish formations). The disease does not lead to the development of atherosclerosis.
- Familial hyper-beta-lipoproteinemia. With this pathology, the number of beta-lipoproteins increases, and sometimes pre-beta lipoproteins. The analysis significantly exceeded the level of cholesterol. Triglycerides may be normal or slightly elevated. Patients also develop xanthomatosis ( xanthomas on the skin). Significantly increases the risk of atherosclerosis. With this disease, myocardial infarction is possible even at a young age.
- Familial hypercholesterolemia with hyperlipemia. In the blood, the level of both cholesterol and triglycerides is significantly increased. Xanthomas are large and appear after 20-25 years. Increased risk of developing atherosclerosis.
- Hyper-pre-beta-lipoproteinemia. In this case, the level of triglycerides rises, and the level of cholesterol remains within the normal range. The disease is often combined with diabetes, gout or obesity.
There are also secondary symptomatic) hyperlipoproteinemia in the following diseases:
- Diabetes. In this case, the excess of lipids in the blood is explained by the transformation of excess carbohydrates.
- Acute pancreatitis. With this disease, the absorption of lipids is impaired, and their level in the blood increases due to the breakdown of adipose tissue.
- Hypothyroidism. The disease is caused by a lack of thyroid hormones, which regulate, among other things, lipid metabolism in the body.
- Intrahepatic cholestasis and other pathologies of the liver. The liver is involved in the synthesis of most lipids needed by the body. With various hepatitis, disorders of the outflow of bile and other pathologies of the liver and bile ducts, the level of lipids in the blood may increase.
- nephrotic syndrome. This syndrome develops when the glomerular apparatus of the kidneys is damaged. Patients present with severe renal edema. In the blood, the level of proteins decreases, and the level of cholesterol rises significantly.
- Porfiry. Porphyria is a disease with a hereditary predisposition. In patients, the metabolism of a number of substances is disturbed, as a result of which porphyrins accumulate in the blood. In parallel, lipid levels may increase ( sometimes significantly).
- Some autoimmune diseases. In autoimmune diseases, antibodies produced by the body attack their own cells. In most cases, chronic inflammatory processes develop, which are associated with an increase in lipid levels.
- Gout. With gout, the metabolism of uric acid is disturbed in the body, and it accumulates in the form of salts. This is partly reflected in lipid metabolism, although their level in this case is slightly increased.
- Alcohol abuse. Alcohol abuse leads to pathologies of the liver and gastrointestinal tract. A number of enzymes that increase blood lipid levels can be activated.
- Taking certain medications. An increase in lipid levels can be caused, for example, by long-term use of oral contraceptives ( contraceptives). Most often, this side effect is mentioned in the instructions for the corresponding drug. Before taking the test, such drugs should not be taken, or the radiation doctor should be warned about this so that he correctly interprets the results of the analysis.
Also, an increased level of lipoproteins in the blood can be observed during pregnancy. This increase is usually small. With an increase in lipid levels 2 to 3 times higher than normal, the likelihood of pregnancy should be considered in combination with other pathologies that cause an increase in lipid levels.
What diseases of the digestive system are associated with lipid metabolism?
A healthy digestive system is essential for good absorption of lipids and other nutrients. A significant imbalance of lipids in food for a long time can lead to the development of some pathologies of the stomach. One of the most common problems in cardiology is atherosclerosis. This disease occurs due to the deposition of lipids in the vessels ( predominantly in arteries). As a result of this process, the lumen of the vessel narrows and blood flow becomes more difficult. Depending on which arteries are affected by atherosclerotic plaques, patients may experience different symptoms. The most characteristic are high blood pressure, coronary heart disease ( sometimes myocardial infarction), the appearance of aneurysms.Atherogenic lipids are those substances that lead to the development of atherosclerosis. It should be noted that the division of lipids into atherogenic and non-atherogenic is very conditional. In addition to the chemical nature of substances, many other factors contribute to the development of this disease.
Atherogenic lipids more often lead to the development of atherosclerosis in the following cases:
- heavy smoking;
- heredity;
- diabetes;
- overweight ( obesity);
- sedentary lifestyle ( hypodynamia) and etc.
07.04.2009
In the diet, fats make up approximately 44 percent. Recommendations for proper diet suggest that this figure should not exceed 30 percent of total calories, and 25 percent would be even better.
Your fat intake should lean toward polyunsaturated and monounsaturated fats, with a maximum of 10 percent or less saturated fat of that total 25 percent fat.
* To reduce fat when making an omelette, remove the yolk of every second egg, this will reduce fat and cholesterol levels, and you won’t even feel the difference.
* Cottonseed oil is 25 percent saturated fat and not the best to use.
* Soybean oil changes flavor when stored for a long time, due to changes in the levels of linolenic acid it contains.
* Sixty-four percent of the calories from caviar are from fat.
* Butter absorbs refrigerator odors, so it should be stored in a closed container.
* Butter keeps in the refrigerator for only two weeks. If you need to keep it for a longer time, keep it in the freezer.
* Eight ounces of potato chips equals 12 to 20 teaspoons of fat.
* Try using water instead of fat in some recipes. It's true that fats are used to make dressings, etc., the flavor becomes even, but if you mix water with flour, cornstarch (cornmeal) or potato starch, it saves you 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 used to make 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 candy is, in most cases, 85 percent saturated fat.
* The use of non-stick cookware and vegetable oil sprays will reduce fat intake.
* Never eat a salad dressing or mayonnaise-based salad until you are sure it has been refrigerated before you are ready to eat it. Neglecting this is the culprit in thousands of cases of food poisoning, every year.
* Oils related to fish are more beneficial than those related to meat. Fish contains a high percentage of omega fatty acids.
* Any margarine containing coconut or palm oil will have a very high level of saturated fat. On the labels they are now called tropical oils (oils of tropical plants).
* New fat substitutes continue to appear in our products. Do not forget that they are still synthetic production, and not a natural product. They should not be considered as a panacea to replace fats in our diet.
* The best butter is made from sweet cream grade AA.
* An ounce of sunflower seeds contains 160 calories and is not considered a dietary snack food.
* A burrito topped with sour cream and guacamole (a sauce of mashed avocado, spiced tomatoes and mayonnaise) can contain up to 1,000 calories and 59 percent fat.
*Studies have shown that stearic acid, one of the saturated fats, has little effect on raising cholesterol levels.
*New Reduced Fat Peanut Butter has the same number of calories per serving as regular peanut butter, approximately 190 calories per serving, and sweeteners have been added instead of fat.
* When you store some oils in the refrigerator, they may become hazy (not clear, light haze), this is due to the formation of harmless crystals. Manufacturers sometimes refrigerate oils before they are released for sale and remove these crystals in a process called winterizing. These oils will now remain clear when cooled.
* Pork fat has large crystals, while butter is small. 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 dieters miss fat more than sweets.
*People on a high-fat diet are more prone to colon cancer, prostate cancer, or breast cancer. Future research may show that it also has a detrimental effect on the immune system.
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Lipids - what is it? Translated from Greek, the word "lipids" means "small particles of fat." They are a group of compounds of natural organics of an extensive nature, including directly fats, 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, and complex ones contain high-molecular 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 an energy reserve of the body and the provision of water-repellent properties of the skin, coupled with thermal insulation protection. Some fat-containing substances that do not have fatty acids are also classified as lipids, for example, terpenes. Lipids are not affected by the aquatic environment, but are easily soluble 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 is it?" 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 overall 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, the relationship and exchange of signals in the intercellular environment cannot do without fatty acids.
Lipids - what are they, if they are considered from the standpoint of spontaneously occurring steroid hormones, phosphoinositides and prostaglandins? This is, first of all, the presence in the 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 complex with albumins, and water-soluble lipoproteins are transported in the usual way.
Lipid classification
The categorization of compounds of a biological nature is a process that involves some controversial issues. Lipids in connection with biochemical and structural properties can be attributed equally to different categories. The main classes of lipids include simple and complex compounds.
The simple ones are:
- 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-alcohol.
Complex lipids:
- Phospholipid compounds - with the inclusion of nitrogenous components, glycerophospholipids, ofphingolipids.
- Glycolipids - 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 material for cell membranes. Participate in the transport of various substances around the periphery of the body. Fat layers based on lipid structures help protect the body from hypothermia. They have the function of energy accumulation "in reserve".
Fat reserves are concentrated in the cytoplasm of cells in the form of droplets. Vertebrate animals, including humans, have special cells - adipocytes, which are able to contain quite a lot of fat. The placement of fat accumulations in adipocytes occurs due to lipoid enzymes.
biological functions
Fat is not only a reliable source of energy, it also has thermal insulating properties, which is facilitated by biology. Lipids at the same time allow you to achieve several useful functions, such as the 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 an 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 necessary for normal cellular activity. One biomembrane microparticle contains more than a million lipid molecules that have dual characteristics: they are both hydrophobic and hydrophilic. As a rule, these mutually exclusive properties are non-equilibrium in nature, and therefore their functional purpose looks quite logical. Lipids in the cell 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 performs a specific function.
Lipids in the human diet
Triglycerides - nature, are an efficient source of energy. acids are found in meat and dairy products. And fatty acids, but unsaturated, are found in nuts, sunflower and olive oils, seeds and corn grains. So that the level of cholesterol in the body does not increase, it is recommended to limit the daily rate of animal fats to 10 percent.
Lipids and carbohydrates
Many organisms of animal origin "stack" fats at certain points, subcutaneous tissue, in the folds of the skin, and other places. The oxidation of lipids in such fatty deposits is slow, and therefore the process of their conversion into carbon dioxide and water provides a significant amount of energy, almost twice as much as carbohydrates can provide. In addition, the hydrophobic properties of fats eliminate the need to use large amounts of water to promote hydration. The transition of fats into the energy phase occurs "dry". However, fats are much slower 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 life of the body.
Lipids (from Greek. lipos fat) includes fats and fat-like substances. They are contained in almost all cells - from 3 to 15%, and in the cells of subcutaneous adipose tissue they are 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 share some properties. These organic substances do not dissolve in water, but are readily soluble in organic solvents: ether, benzene, gasoline, chloroform, etc. This property is due to the fact that non-polar and hydrophobic structures predominate in lipid molecules. All lipids can be divided into fats and lipoids.
Fats
The most common are fats(neutral fats, triglycerides), which are complex compounds of the trihydric alcohol 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, 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. Fatty acids contain a carboxyl group (-COOH). It is easily ionized. With its help, fatty acid molecules are connected to other molecules.
All fatty acids are divided into two groups - rich and unsaturated . Unsaturated fatty acids do not have double (unsaturated) bonds, saturated ones do. Saturated fatty acids include palmitic, butyric, lauric, stearic, etc. Unsaturated fatty acids include 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 usually firm in texture. These are the fats of many animals, coconut oil. Fats that contain unsaturated fatty acids have a low melting point. These fats are mostly liquid. Vegetable fats of a liquid consistency run up oils . These fats include fish oil, sunflower, cottonseed, linseed, hemp oils, etc.
Lipoids
Lipoids can form complex complexes with proteins, carbohydrates and other substances. The following connections can be distinguished:
- Phospholipids. They are complex compounds of glycerol and fatty acids and contain a phosphoric acid residue. All phospholipids have a polar head and a non-polar tail formed by two fatty acids. The main components of cell membranes.
- Waxes. These are complex lipids, consisting of more complex alcohols than glycerol and fatty acids. They perform a protective function. Animals and plants use them as water-repellent and drying agents. Waxes cover the surface of the leaves of plants, the surface of the body of arthropods living on land. Waxes secrete the sebaceous glands of mammals, the oil gland of birds. Bees build honeycombs from wax.
- Steroids (from the Greek stereos - solid). These lipids are characterized by the presence of not carbohydrate, but more complex structures. Steroids include important substances of the body: vitamin D, hormones of the adrenal cortex, gonads, bile acids, cholesterol.
- Lipoproteins and glycolipids. Lipoproteins are made up of proteins and lipids, while glucoproteins are made up 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.
Functions of lipids
Fats are the main type hoarding substances. They are stored in the seed, subcutaneous adipose tissue, adipose tissue, fat body of insects. The reserves of fats significantly exceed the reserves of carbohydrates.
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 needed by the body. The breakdown of 1 g of fat releases 38.9 kJ of energy. 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 the delicate internal organs from shock, shock, and damage.
Thermal insulation. Fats do not conduct heat well. Under the skin of some animals (especially marine), 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 fatty tissue called brown fat. It has such a color because it is rich in red-brown mitochondria, as they contain iron-containing proteins. This tissue produces the thermal energy needed by animals in conditions of low temperatures.
temperatures. Brown fat surrounds the vital organs (heart, brain, etc.) or lies in the path of the blood that rushes to them, and thus directs heat to them.
Suppliers of endogenous water
When 100 g of fat is oxidized, 107 ml of water is released. Thanks to this water, many desert animals exist: camels, jerboas, etc. Animals during hibernation also produce endogenous water from fats.
A fatty substance covers the surface of the leaves, preventing 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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