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 an autonomous system, fenced off from the outside world, and on the other, each cell can exchange molecules with others and with the 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. The breakdown of the main part of 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 alkaline environment, 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 structures and, accordingly, lipids perform different functions.
- Unsaponifiable. In an alkaline environment they do not form salts carboxylic acids. Biological chemistry includes fatty acids, derivatives of polyunsaturated fatty acids - eicosanoids, cholesterol, as the most prominent representative of the main class of sterols-lipids, as well as its derivatives - steroids and some other substances, for example, vitamins A, E, etc.
General classification of lipids
Fatty acid
Substances that belong to the group of so-called simple lipids and are of great importance for the body are fatty acids. Depending on the presence of double bonds in the non-polar (water-insoluble) carbon “tail”, fatty acids are divided into saturated (do not have double bonds) and unsaturated (have one or even more 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 for the synthesis of eicosanoids is arachidonic acid, which is one of the most important unsaturated fatty acids. It is eicosanoids that are responsible for the flow of inflammatory processes.
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 of the immune system into tissues.
- With the help of chemicals, they mediate the movement of immune cells, the release of enzymes and the absorption of particles foreign to the body.
But the role of eicosanoids in the human body does not end there; they are also responsible for the blood coagulation system. Depending on the situation, eicosanoids can dilate blood vessels, relax smooth muscle, reduce aggregation or, if necessary, cause the opposite effects: vasoconstriction, contraction of smooth 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 of surfactant ─ a substance that ensures breathing processes, namely, preventing the alveoli from collapsing 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, and heart 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 significance 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 most quickly and clearly manifested by disorders of cholesterol metabolism, the predominance of atherogenic carriers (so-called low- and very low-density lipoproteins) over antiatherogenic ones (lipoproteins with high density).
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 the 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.
They are organic compounds insoluble in water. They consist of fatty acid molecules connected in a chain of hydrogen and carbon atoms. If the carbon atoms are connected to each other by a strong bond, then such fatty acids are called “saturated.” Accordingly, if the carbon atoms are loosely bonded, then the fatty acids are unsaturated. The most important fatty acids for the human body are arachidonic, linoleic, and oleic fatty acids.
Division by chemical formula for saturated and unsaturated acids was developed quite a long time ago. Unsaturated ones, in turn, are divided into polyunsaturated and monounsaturated. Today it is known that saturated acids in our food can be found in pates, meat, milk, eggs. And unsaturated ones are found in olive, peanut, sunflower oil; fish, goose and duck fat.
The term “lipids” refers to the entire spectrum of fat-like substances extracted with fat solvents (chloroform, ether, gasoline).
Lipids include triacylglycerol esters. These are substances in which glycerol binds to three fatty acid residues. Lipids include oils and fats. Oils contain a large amount of unsaturated acids and have a liquid consistency (with the exception of margarines). Fats, on the contrary, have a solid structure and contain large amounts of saturated acids.
Depending on their origin, lipids are divided into two main categories:
- Vegetable fats (olive oil, nut butter, margarine, etc.).
- Animal fats (found in fish, meat, cheese, butter, cream, etc.).
When fats combine with “bad” carbohydrates, metabolism is disrupted, and as a result, most of them are deposited in the body as fatty layers.
As a rule, in our diet there is an excess of fat - fried fatty foods, in particular fast food, are becoming more and more popular and familiar. At the same time, food may well be tasty, even if you refuse sunflower oil and butter when preparing it.
Some of the lipids directly affect the increase in cholesterol levels in the blood. Cholesterol can be roughly divided into “good” and “bad”. The goal of a healthy diet is the dominance of “good” cholesterol over “bad” cholesterol. The overall blood level of this substance should be normal. If there is too much cholesterol, then it is deposited on the walls of our blood vessels and disrupts blood circulation, which disrupts the trophism of organs and tissues. And insufficient blood supply, in turn, leads to serious disruption of organ functioning. The main danger is the possibility of a blood clot breaking off from the wall and being carried by the blood flow throughout the body. His blood clot will clog the blood vessels of the heart, causing instant death. Everything happens so instantly that there is simply no chance of helping and saving a person.
Not all fats increase the amount of “bad” cholesterol in the blood; some of them, on the contrary, lower its level.
- Fats that increase cholesterol levels are found in butter, lard, meat, cheese, smoked and dairy products, and palm oil. These are saturated fats.
- Fats that almost do not contribute to the formation of cholesterol are found in eggs, oysters, and poultry meat (without skin).
- Fats that help lower cholesterol are vegetable oils: olive, rapeseed, corn, sunflower.
Saturated
Frequent consumption of saturated fats causes serious harm to health. Sausages, lard, butter and cheese should not form the basis of the diet. By the way, saturated fatty acids are found in both palm and coconut oil. When buying products in a store, pay attention to the composition of the ingredients included in them. Palm oil is a frequent “guest” in our diet, although we don’t always know about it. However, some housewives will use it for baking instead of margarine. Meat contains stearic acid, which is contraindicated for the body in large quantities. The amount of fat in the daily diet should not exceed 50 grams. The optimal nutritional balance should consist of 50% monounsaturated fatty acids, 25% polyunsaturated and 25% saturated.Most of People consume too much saturated fat at the expense of unsaturated fat. Of these, about 70% are “invisible” (sausages, aperitif sets, cheeses, chips, and, of course, meat), and 30% are “visible” (this is everything that can be used for frying dishes and spreading on bread) .
Those fats that the body has not used remain in reserve in the body and, when combined with sugars, become the main cause of excess weight. And only physical activity and a balanced diet can correct this situation. Therefore, it is extremely important to adjust the intake of fatty acids according to their expenditure.
Monounsaturated
This type of fat is found in vegetable oils, and its main component is oleic monounsaturated acid. Mono unsaturated fats neutral in relation to the body, and do not affect either the tendency to thrombosis or the level of cholesterol in the blood.Olive oil is great for cooking, as it can withstand fairly high temperatures (in fact, up to 210°C), and at the same time retains a significant part of its valuable properties. It is advisable to buy unrefined, cold-pressed oil, and the darker the color it is, the better. It must be stored in a dark and cool place.
To obtain one liter of oil you need 5 kg of black olives. The cold pressing technique retains most of all vitamins and mineral salts in the oil: copper, phosphorus, magnesium, calcium, potassium, copper, iron. Interesting fact: the balance of lipids in olive oil is almost the same as in breast milk.
Of all the oils, olive oil is the best absorbed, and it also helps with constipation and liver failure. Another one of his useful property is that it can neutralize the intoxication of the body after drinking alcohol. Recent studies have shown that olive oil increases calcium absorption levels. This means that it is indispensable in the diet of children at the age when their bone apparatus is formed and developing.
Oleic acid is found in: olive oil (77%), rapeseed oil (55%), peanut oil (55%), grape seed oil (41%), soybean oil (30%), sunflower oil (25%), in wheat germ oil (25%), in wheat germ oil walnuts (20%).
Polyunsaturated
They consist of two groups, in which active substance is the so-called essential fatty acid. Since the body cannot produce it on its own, this acid must come from food.
Main sources: cereal sprouts (up to 50% fatty acid content), corn, oatmeal, brown rice, and oils.
Linoleic acid (Omega-6) is found in: sunflower oil (57%), soybean oil (55%), grape seed oil (54%), walnut oil (54%), wheat germ oil (53%) , in pumpkin (45%), sesame (41%), peanut (20%), rapeseed (20%), olive (7%).
Linolenic acid (Omega-3): in flaxseed oil (55%), walnut oil (13%), canola oil (8%), wheat germ oil (6%), soybean oil (6%), sesame oil (1 %), olive (0.8%). Omega-3 is also found in fish.
Flaxseed oil is very rich in omega-6 and omega-3 unsaturated fatty acids, which are necessary for cell building. It softens the skin, helps the body fight allergies, protects brain and nerve structures, and stimulates the production of hormones. It must not be heated and cannot be cooked on it. Flaxseed oil is added exclusively to ready-made cooled dishes: soups, cereals, salads, vegetables.
Fish and fish oil are a valuable source of omega-3 fatty acids. It is these acids that our body needs most. They are very useful for brain activity. However, the current ecology is such that it is advisable to give a child sea fish, not pure fish oil. It is made from cod liver, and the liver tends to accumulate various toxins in high doses. In addition, when eating cod liver, there is a high probability of an overdose of vitamins A and D. For people who eat vegetarian food, flaxseed oil is a good replacement for fish oil.
Food supplements that are valuable sources of polyunsaturated fatty acids:
- Pollen.
- Sprouted wheat.
- Brewer's yeast.
- Aspen and borage oils (they can be found in pharmacies in capsule form).
- Soy lecithins.
In addition to some oils
The table provides data on the critical temperatures of some oils (in degrees Celsius), at which they decompose and release carcinogenic toxic substances that primarily affect the liver.Oils sensitive to light and heat
- Walnut oil.
- Pumpkin.
- Linen.
| Oils | mg per 100g oil |
| From wheat sprouts | 300 |
| From walnuts | 170 |
| Soy | 94 |
| Corn | 28 |
| Olive | 15 |
It is better not to eat coconut oil. It contains too many fatty acids. However, many people, especially those living in areas where coconut oil is produced, consider it a literal panacea for all ills. This is one of the oldest types of oils extracted by people. It is extracted from compressed dried coconut fruits. On the other hand, the good thing about coconut oil is that the saturated fat it contains has a completely different structure than the saturated fat used in fast food. That is why there is still debate about whether this oil is harmful or not.
Butter is, on the one hand, an excellent source of vitamins A and D, and on the other hand, cholesterol. But small children have a small amount butter will be useful because when the body is actively growing, it requires saturated fats for the harmonious and complete development of the brain.
What you should definitely know about butter: it absolutely does not tolerate heating above 120°. This means that you cannot fry food on it. Upon contact with the hot surface of the frying pan, the oil immediately begins to release carcinogenic substances that affect the intestines and stomach.
Margarine is an intermediate product between vegetable oil and butter. It was created as a substitute for butter. The composition of margarines may vary from one manufacturer to another. Some are enriched with wheat germ oil, while others contain only saturated fatty acids or are hydrogenated.
If you carry out a minimum of processing, that is, do not hydrogenate margarine, then some vitamins are retained in it. But it must be remembered that the hardness of margarine depends on the amount of palm and coconut oils added to it. Therefore, those who are prone to cardiovascular diseases are not recommended to use margarine.
Paraffin oil is a petroleum derivative and should be avoided. When using paraffin oil for food, the absorption of fat-soluble vitamins worsens. Moreover, when oil is excreted from the intestines, it binds to already dissolved vitamins and comes out along with them.
Functions of fats
Lipids in our body perform energy and plastic functions. Unsaturated fatty acids are essential because not all of them are synthesized in the body. They are precursors of prostaglandins. Prostaglandins are hormones that maintain the liquid state of cellular lipids, and also prevent the development of atherosclerotic plaques and prevent cholesterol and other lipids from sticking to the walls of blood vessels.Phospholipids are the fundamental structures of most cell membranes. They are part of white and gray matter nervous tissue.
Fats by their nature are excellent solvents. Those substances that do not dissolve in water are highly soluble in fats. Most of the fat accumulates in adipose tissue cells, which are fat depots. Depot can account for up to 30% of body weight. The function of adipose tissue is to fix neurovascular bundles and internal organs. Fat is a thermal insulator that retains heat, particularly in childhood. Lipid metabolism closely related to protein and carbohydrate metabolism. When excess carbohydrates enter the body, they can turn into fats. In unfavorable conditions for the body, during fasting, fats turn back into carbohydrates.
The energy function is that lipids from all nutrients give the body the greatest amount of energy. It has been proven that the oxidation of 1 gram of fat releases 9.3 kilocalories of heat, which is twice as much as the oxidation of 1 gram of proteins or carbohydrates. The oxidation of 1 g of proteins and carbohydrates releases 4.1 kcal of heat.
Food fats
Triacylglycerols predominate among them. There are vegetable and animal fats, and vegetable fats are more complete because they contain much more unsaturated acids. A small amount of free fatty acids is also ingested with food. Normally, up to 40% of all calories consumed by our body come from lipids.Absorption and digestion of fats
Digestion of fats is a process of enzymatic hydrolysis, which occurs in the small intestine and duodenum under the influence of enzyme substances found in the juices of the pancreas and intestinal glands.In order for fats to be digested, the body must produce bile. It contains detergents (or bile acids) that emulsify lipids so that enzymes can break them down better. Products that are formed as a result of digestive hydrolysis - fatty acids, bile acids and glycerol - are absorbed from the intestinal cavity into the mucosal cells. In these cells, fat is resynthesized again and forms special particles called “chylomicrons”, which are sent to the lymph and lymphatic vessels, and then enter the blood through the lymph. In this case, only a small part of the fatty acids formed during the hydrolysis process, which have a relatively short carbon chain (in particular, these are the hydrolysis products of dairy fats) are absorbed and enter the blood of the portal vein, and then into the liver.
The role of the liver in lipid metabolism
The liver is responsible for the processes of mobilization, processing and biosynthesis of lipids. Short-chain fatty acids, combined with bile acids, travel from the digestive tract through the portal vein into the bloodstream into the liver. These fatty acids do not participate in the processes of lipid synthesis and are oxidized with the assistance of liver enzyme systems. In adults, they generally do not play an important role in metabolism. The only exception is children; their diet contains the most fat from milk.Other lipids enter through the hepatic artery as lipoproteins or chylomicrons. They are oxidized in the liver, as in other tissues. Most of the lipids, except for a few unsaturated ones, are newly synthesized in the body. Those of them that are not synthesized must be ingested along with food products. The overall process of fatty acid biosynthesis is called “lipogenesis”, and it is the liver that is most intensively involved in this process.
Enzymatic processes of transformation of phospholipids and cholesterol are carried out in the liver. The synthesis of phospholipids ensures the renewal of the structural units of its cell membranes in the liver.
Blood lipids
Blood lipids are called lipoproteins. They are associated with different protein fractions of the blood. Their own fractions during centrifugation are separated according to their relative density.The first fraction is called "chylomicrons"; they consist of a thin protein shell and fats. The second fraction is lipoproteins with very low density. They contain a large amount of phospholipids. The third fraction is lipoproteins, containing a lot of cholesterol. The fourth fraction is high-density lipoproteins; they contain the most phospholipids. The fifth fraction is lipoproteins with high density and low content.
The function of lipoproteins in the blood is to transport lipids. Chylomicrons are synthesized in the intestinal mucous cells and carry fat that has been resynthesized from the products of fatty hydrolysis. Chylomicron fats are supplied, in particular, to adipose tissue and liver. Cells of all body tissues can consume chylomicron fatty acids if they have the necessary enzymes.
Very low density lipoproteins transport exclusively fats that are synthesized in the liver. These lipids are consumed, as a rule, by adipose tissue, although they can also be used by other cells. Fatty acids of high-density lipoproteins are products of the enzymatic breakdown of fat contained in adipose tissue. This faction has a kind of mobility. For example, during a fast, up to 70% of the body’s total energy expenditure is covered by fatty acids from this particular fraction. Phospholipids and cholesterol of high- and low-density lipoprotein fractions are a source of exchange with their corresponding components of cell membranes, with which these lipoproteins can interact.
Transformation of lipids in tissues
In tissues, lipids are broken down under the influence of various lipases, and the resulting fatty acids are added to other formations: phospholipids, cholesterol esters, etc.; or they are oxidized to final products. Oxidation processes occur in several ways. One part of fatty acids oxidative processes in the liver, produces acetone. In severe diabetes mellitus, lipoid nephrosis and some other diseases, the amount of acetone bodies in the blood increases sharply.
Regulation of fat metabolism
The regulation of lipid metabolism is carried out through a rather complex neurohumoral pathway, with the mechanisms predominating in it humoral regulation. If the functions of the gonads, pituitary gland, thyroid gland decrease, the processes of fat biosynthesis increase. The saddest thing is that not only the synthesis of lipids increases, but also their deposition in adipose tissue, and this leads to obesity.Insulin is a hormone of the pancreas and is involved in the regulation of lipid metabolism. Since there is a cross-possibility of transformation of carbohydrates into fats, and then fats into carbohydrates, with insulin deficiency, the processes of carbohydrate synthesis are enhanced, which is accompanied by an acceleration of lipid breakdown processes, during which intermediate metabolic products are formed that are used for the biosynthesis of carbohydrates.
Phospholipids are close in structure to triacylglycerols, only their molecules contain phosphorus-containing groups. Steroids are derivatives of cholesterol and have a different structure. Lipids can also include a large group of fat-soluble substances, which includes vitamins A, D, K, E. Lipids are needed not only to create the lining of our body - they are necessary for hormones, for brain development, for blood vessels and nerves, for the heart. It is known that lipids make up 60% of the brain.
Disturbance of normal blood lipid concentrations
If there is an abnormality in the blood increased level lipids, then pathological condition called hyperlipemia. With hypothyroidism, nephrosis, diabetes and disorders, doctors are faced with a secondary form of hyperlipemia. These diseases cause high levels of cholesterol and triglycerides. Primary hyperlipemia is a fairly rare hereditary pathology that contributes to the development of arteriosclerosis and coronary disease.
During hypoglycemia, fasting, after injections of growth hormone, adrenaline, the amount of free fatty acids in the body sharply increases and mobilization of previously deposited fat begins. This form of the disease is called mobilization hyperlipemia.
With hypercholesterolemia in the blood serum there is high level cholesterol and moderate fatty acids. When interviewing close relatives, their medical history will necessarily reveal cases of early atherosclerosis. Hypercholesterolemia even in early age may contribute to the development of myocardial infarction. Usually, external symptoms not visible. When a disease is detected, treatment is carried out with diet therapy. Its essence is to replace saturated acids with unsaturated acids. Correct diet correction significantly reduces the likelihood of developing pathologies of the vascular system.
With dyslipidemia, the balance of various types of lipids in the blood is disturbed. In particular, the main lipids contained in the blood are cholesterol and triglycerides in different proportions. It is the imbalance that leads to the development of diseases.
High content low-density lipids in the blood, as well as low level high density cholesterol are serious factors risk of cardiovascular complications in patients with diagnosed type 2 diabetes mellitus. Abnormal levels of lipoproteins in in this case may result from improper glycemic control.
Dyslipidemia is considered the main cause of the development of atherosclerotic changes.
Factors influencing the development of dyslipidemia
Most significant reasons dyslipidemia formations are genetic disorders lipid metabolism. They consist of mutations in the genes responsible for the synthesis of apolipoproteins - the components of lipoproteins.The second important factor is healthy/unhealthy lifestyle. Under unfavorable circumstances, lack of physical activity, and drinking alcohol, lipid metabolism is disrupted. Obesity is directly related to increased triglyceride levels and impaired cholesterol concentrations.
Another factor in the development of dyslipidemia is psychoemotional stress, which through neuroendocrine stimulation contributes to lipid metabolism disorders. Neuroendocrine stimulation refers to increased activity of the autonomic nervous system.
The clinical classification of types of dyslipidemia involves dividing them into so-called primary and secondary. Among the primary ones, we can distinguish polygenic (acquired during life, but due to hereditary disposition), and monogenic (genetically determined family diseases).
Reason secondary form diseases can be: alcohol abuse, insufficient kidney function, diabetes, cirrhosis, hyperthyroidism, medications that cause side effects (antiretroviral drugs, progestins, estrogens, glucocorticosteroids).
Diagnostic methods used to diagnose dyslipidemia include determining lipoprotein levels (high and low density), total cholesterol, and triglycerides. During the daily cycle, even completely healthy people experience fluctuations in cholesterol levels of about 10%; and fluctuations in triglyceride levels - up to 25%. To determine these indicators, blood donated on an empty stomach is centrifuged.
Definition lipid profile It is recommended to carry out once every five years. At the same time, it is desirable to identify other potential risk factors for the development of cardiovascular pathologies (smoking, diabetes mellitus, a history of ischemia in close relatives).
Atherosclerosis
The main factor in the appearance of ischemia is the formation of many small atherosclerotic plaques, gradually increasing in the lumens of the coronary arteries and narrowing the lumen of these vessels. In the early stages of the disease, plaques do not impair blood flow, and the process does not manifest itself clinically. The gradual growth of the plaque and the simultaneous narrowing of the vessel duct can provoke the manifestation of signs of ischemia.
First, they will begin to appear during intense physical stress, when the myocardium requires more oxygen and this need cannot be met by an increase in coronary blood flow.
The clinical manifestation of the ischemic state of the myocardium is a sharp attack of angina. It is accompanied by such phenomena as pain and a feeling of constriction behind the sternum. The attack passes as soon as the stress of an emotional or physical nature stops.
Doctors consider lipid metabolism disorders to be the main (but not the only main) cause of ischemia, but besides this, significant factors are smoking, obesity, disorders carbohydrate metabolism And genetic predisposition. Cholesterol levels directly affect the occurrence of complications of heart disease.
Treatment for this disease consists of normalizing cholesterol levels. To achieve this, diet correction alone is not enough. It is also necessary to combat other risk factors for development: reduce weight, increase physical activity, quit smoking. Nutrition correction involves not only reducing the total calorie content of food, but also replacing animal fats with vegetable fats in the diet: reducing
consumption of animal fats and a simultaneous increase in consumption of vegetable fats and fiber. We must remember that a significant part of the cholesterol in our body does not come with food, but is formed in the liver. Therefore, diet is not a panacea.
Used to lower cholesterol levels medications- nicotinic acid, estrogen, dextrothyroxine. Of these drugs, it is most effective against ischemia a nicotinic acid, however, its use is limited due to the associated side effects. The same applies to other medications.
In the 80s of the last century, know-how began to be used in lipid-lowering therapy - drugs from the group of statins. There are currently 6 drugs belonging to this group available on the pharmaceutical market. Pravastatin and lovastatin are drugs based on fungal waste products. Rosuvastatin, atorvastatin, fluvastatin are synthetic drugs, and simvastatin is semi-synthetic.
These drugs help reduce low-density lipoprotein levels, reduce total cholesterol, and to a lesser extent, triglycerides. Several studies have also shown a reduction in overall mortality among ischemic patients.
Cardiosclerosis
This disease is a complication of atherosclerosis and consists of replacement of the myocardium with connective tissue. Connective tissue is not elastic, unlike the myocardium; accordingly, the elasticity of the entire organ on which the inelastic “patch” appears suffers, and the heart valves become deformed.Cardiosclerosis (or myocardiosclerosis) is a logical consequence of an untreated disease: myocarditis, atherosclerosis, rheumatism. Acute development of this disease occurs with myocardial infarction and coronary disease. When atherosclerotic plaques occur throughout the coronary arteries in the heart, then the blood supply to the myocardium suffers, it lacks oxygen carried by the bloodstream.
The acute form of ischemic disease is myocardial infarction. So the wrong way of life, unbalanced diet and smoking can become an implicit cause of a heart attack, and acute psycho-emotional stress, against the background of which a heart attack appears, is a visible, but far from the main reason.
In addition to the acute form, there is also a chronic form. It is manifested by regularly occurring attacks of angina (that is, chest pain). You can relieve pain during an attack with nitroglycerin.
The body is designed in such a way that it tries to decompensate for any violation. Scars from connective tissue do not allow the heart to stretch and contract elastically. Gradually, the heart adapts to the scars and simply increases in size, which leads to disruption of blood circulation through the vessels, disruption of muscle contractility, and expansion of the cardiac cavities. All this together causes insufficiency of heart function.
Cardiosclerosis is complicated by a violation heart rate(extrasystole, arrhythmia), protrusion of a fragment of the heart wall (aneurysm). The danger of an aneurysm is that the slightest tension can cause it to rupture, which leads to instant death.
Diagnosis of the disease is carried out using an electrocardiogram and ultrasound of the heart.
Treatment consists of the following: identifying and treating exactly the disease that was main reason development of cardiosclerosis; compliance bed rest in the event that the disease has led to myocardial infarction (at rest, scarring and healing occurs without the formation of a dangerous aneurysm); normalization of rhythm; stimulation of metabolic processes in the heart muscle, limitation of any stress; maintaining a properly balanced diet, in particular, reducing the amount of lipids in the diet.
The diet has a good anti-allergic and anti-inflammatory effect, and is also considered an excellent preventive measure for the prevention of heart disease.
The basic rule of nutrition is moderation in the amount of food. It is also useful to lose extra pounds, which put a strain on the heart. The selection of food products should be carried out from the point of view of their value as energy and plastic materials for the heart. It is imperative to exclude spicy, sweet, fatty, and salty foods from food. Use alcoholic drinks Contraindicated for patients with vascular disorders. Food should be enriched with minerals and vitamins. Fish, boiled meat, vegetables, fruits, dairy products should be the basis of the diet.
LIPIDS - this is a heterogeneous group of natural compounds, completely or almost completely insoluble in water, but soluble in organic solvents and in each other, yielding high molecular weight fatty acids upon hydrolysis.
In a living organism, lipids perform various functions.
Biological functions of lipids:
1) Structural
Structural lipids form complex complexes with proteins and carbohydrates, from which the membranes of cells and cellular structures are built, and participate in a variety of processes occurring in the cell.
2) Spare (energy)
Reserve lipids (mainly fats) are the body's energy reserve and participate in metabolic processes. In plants they accumulate mainly in fruits and seeds, in animals and fish - in subcutaneous fatty tissues and tissues surrounding internal organs, as well as liver, brain and nervous tissues. Their content depends on many factors (type, age, nutrition, etc.) and in some cases accounts for 95-97% of all secreted lipids.
Calorie content of carbohydrates and proteins: ~ 4 kcal/gram.
Caloric content of fat: ~ 9 kcal/gram.
The advantage of fat as an energy reserve, unlike carbohydrates, is its hydrophobicity - it is not associated with water. This ensures compactness of fat reserves - they are stored in anhydrous form, occupying a small volume. The average person's supply of pure triacylglycerols is approximately 13 kg. These reserves could be enough for 40 days of fasting under conditions of moderate physical activity. For comparison: total reserves glycogen in the body - approximately 400 g; when fasting, this amount is not enough even for one day.
3) Protective
Subcutaneous adipose tissue protects animals from cooling, and internal organs from mechanical damage.
The formation of fat reserves in the body of humans and some animals is considered an adaptation to irregular nutrition and living in a cold environment. Animals that hibernate for a long time (bears, marmots) and are adapted to living in cold conditions (walruses, seals) have a particularly large reserve of fat. The fetus has virtually no fat and appears only before birth.
A special group in terms of their functions in a living organism are the protective lipids of plants - waxes and their derivatives, covering the surface of leaves, seeds and fruits.
4) An important component of food raw materials
Lipids are an important component food, largely determining its nutritional value and taste. The role of lipids in various food technology processes is extremely important. Spoilage of grain and its processed products during storage (rancidity) is primarily associated with changes in its lipid complex. Lipids isolated from a number of plants and animals are the main raw materials for obtaining the most important food and technical products (vegetable oil, animal fats, including butter, margarine, glycerin, fatty acids, etc.).
2 Classification of lipids
There is no generally accepted classification of lipids.
It is most appropriate to classify lipids depending on their chemical nature, biological functions, as well as in relation to some reagents, for example, alkalis.
Based on their chemical composition, lipids are usually divided into two groups: simple and complex.
Simple lipids – esters of fatty acids and alcohols. These include fats , waxes And steroids .
Fats – esters of glycerol and higher fatty acids.
Waxes – esters of higher alcohols of the aliphatic series (with a long carbohydrate chain of 16-30 C atoms) and higher fatty acids.
Steroids – esters of polycyclic alcohols and higher fatty acids.
Complex lipids – in addition to fatty acids and alcohols, they contain other components of various chemical natures. These include phospholipids and glycolipids .
Phospholipids are complex lipids in which one of the alcohol groups is not associated with FA, but with phosphoric acid (phosphoric acid can be combined with an additional compound). Depending on which alcohol is included in the phospholipids, they are divided into glycerophospholipids (contain the alcohol glycerol) and sphingophospholipids (contain the alcohol sphingosine).
Glycolipids – these are complex lipids in which one of the alcohol groups is associated not with FA, but with a carbohydrate component. Depending on which carbohydrate component is part of the glycolipids, they are divided into cerebrosides (they contain a monosaccharide, disaccharide or a small neutral homooligosaccharide as a carbohydrate component) and gangliosides (they contain an acidic heterooligosaccharide as a carbohydrate component).
Sometimes into an independent group of lipids ( minor lipids ) secrete fat-soluble pigments, sterols, and fat-soluble vitamins. Some of these compounds can be classified as simple (neutral) lipids, others - complex.
According to another classification, lipids, depending on their relationship to alkalis, are divided into two large groups: saponifiable and unsaponifiable. The group of saponified lipids includes simple and complex lipids, which, when interacting with alkalis, hydrolyze to form salts of high molecular weight acids, called “soaps”. The group of unsaponifiable lipids includes compounds that are not subject to alkaline hydrolysis (sterols, fat-soluble vitamins, ethers, etc.).
According to their functions in a living organism, lipids are divided into structural, storage and protective.
Structural lipids are mainly phospholipids.
Storage lipids are mainly fats.
Protective lipids of plants - waxes and their derivatives, covering the surface of leaves, seeds and fruits, animals - fats.
FATS
The chemical name of fats is acylglycerols. These are esters of glycerol and higher fatty acids. "Acyl" means "fatty acid residue".
Depending on the number of acyl radicals, fats are divided into mono-, di- and triglycerides. If the molecule contains 1 fatty acid radical, then the fat is called MONOACYLGLYCEROL. If the molecule contains 2 fatty acid radicals, then the fat is called DIACYLGLYCEROL. In the human and animal body, TRIACYLGLYCEROLS predominate (contain three fatty acid radicals).
The three hydroxyls of glycerol can be esterified either with only one acid, such as palmitic or oleic, or with two or three different acids:
Natural fats contain mainly mixed triglycerides, including residues of various acids.
Since the alcohol in all natural fats is the same - glycerol, the differences observed between fats are due solely to the composition of fatty acids.
Over four hundred carboxylic acids of various structures have been found in fats. However, most of them are present only in small quantities.
The acids contained in natural fats are monocarboxylic acids, built from unbranched carbon chains containing an even number of carbon atoms. Acids containing an odd number of carbon atoms, having a branched carbon chain, or containing cyclic moieties are present in small quantities. The exceptions are isovaleric acid and a number of cyclic acids contained in some very rare fats.
The most common acids in fats contain 12 to 18 carbon atoms and are often called fatty acids. Many fats contain small amounts of low molecular weight acids (C 2 -C 10). Acids with more than 24 carbon atoms are present in waxes.
The glycerides of the most common fats contain significant quantities of unsaturated acids containing 1-3 double bonds: oleic, linoleic and linolenic. Arachidonic acid containing four double bonds is present in animal fats; acids with five, six or more double bonds are found in fats of fish and marine animals. Most unsaturated acids of lipids have a cis configuration, their double bonds are isolated or separated by a methylene (-CH 2 -) group.
Of all the unsaturated acids contained in natural fats, oleic acid is the most common. In many fats, oleic acid makes up more than half of the total mass of acids, and only a few fats contain less than 10%. Two other unsaturated acids - linoleic and linolenic acid - are also very widespread, although they are present in much smaller quantities than oleic acid. Linoleic and linolenic acids are found in noticeable quantities in vegetable oils; For animal organisms they are essential acids.
Of the saturated acids, palmitic acid is almost as widespread as oleic acid. It is present in all fats, with some containing 15-50% of the total acid content. Stearic and myristic acids are widely used. Stearic acid is found in large quantities (25% or more) only in the storage fats of some mammals (for example, in sheep fat) and in the fats of some tropical plants, such as cocoa butter.
It is advisable to divide the acids contained in fats into two categories: major and minor acids. The main acids of fat are acids whose content in fat exceeds 10%.
Physical properties of fats
As a rule, fats do not withstand distillation and decompose even if they are distilled under reduced pressure.
The melting point, and therefore the consistency of fats, depends on the structure of the acids that make up them. Solid fats, i.e. fats that melt at a relatively high temperature, consist predominantly of glycerides of saturated acids (stearic, palmitic), and oils that melt at a lower temperature and are thick liquids contain significant amounts of glycerides of unsaturated acids (oleic , linoleic, linolenic).
Since natural fats are complex mixtures of mixed glycerides, they do not melt at a certain temperature, but in a certain temperature range, and they are first softened. To characterize fats, it is usually used solidification temperature, which does not coincide with the melting point - it is slightly lower. Some natural fats are solids; others are liquids (oils). The solidification temperature varies widely: -27 °C for linseed oil, -18 °C for sunflower oil, 19-24 °C for cow lard and 30-38 °C for beef lard.
The solidification temperature of fat is determined by the nature of its constituent acids: the higher the content of saturated acids, the higher it is.
Fats are soluble in ether, polyhalogen derivatives, carbon disulfide, aromatic hydrocarbons (benzene, toluene) and gasoline. Solid fats are poorly soluble in petroleum ether; insoluble in cold alcohol. Fats are insoluble in water, but they can form emulsions that are stabilized in the presence of surfactants (emulsifiers) such as proteins, soaps and some sulfonic acids, mainly in a slightly alkaline environment. Milk is a natural fat emulsion stabilized by proteins.
Chemical properties of fats
Fats enter into all chemical reactions characteristic of esters, but their chemical behavior has a number of features associated with the structure of fatty acids and glycerol.
Among the chemical reactions involving fats, several types of transformations are distinguished.
One of the biggest myths of modern humanity is the harmfulness of fats. Fat has become enemy number one. People spend dollars, rubles, euros, etc. to buy low-fat cookies, low-fat cola, tablets that can interfere with the absorption of fats, tablets that dissolve fats. People are on all sorts of fat-free diets.
But... In countries that are prosperous in all respects, the number of people suffering from obesity is steadily growing. The number of people suffering from cardiovascular diseases and diabetes mellitus, that is, diseases largely associated with excess weight, is growing. The war on fat continues...
So what's wrong?
Fact 1: Fats are good for you
The first and main mistake is to assume that all fats are the same; giving up all fats is a good thing. However, the education of the population is quite high, now many people know that unsaturated fats (mainly vegetable fats) are healthy. And the harmful ones are saturated ones (mainly animals).
Let's figure this out.
Saturated fats are structural components of cell membranes and participate in the biochemistry of the body. That's why complete failure from them will lead to irreversible changes in health. Another thing is that their consumption must correspond age indicators. Children and adolescents need them in sufficient quantities; with age, their consumption can be reduced.
Unsaturated fats - reduce the level of “bad” cholesterol, are necessary for the body to absorb certain vitamins (fat-soluble), and participate in metabolism. That is, the body also needs these fats.
A quick observation: saturated fats are solid, unsaturated fats are liquid.
According to physiological indicators for the average person, the ratio of saturated - unsaturated fats should be 1\3:2\3. Eating healthy fats is essential!
Trans fats are definitely harmful. They are also found in nature (for example, in natural milk), but for the most part they are formed from other (vegetable) fats, through hydrogenation (a method of processing fats to give them a solid form).
Fact 2: Body fat is not the result of eating fat.
What?! Of course, if you simply increase your fat intake without reducing other foods, you excess weight dial. The basis of maintaining a normal weight is balance. You should burn as many calories as you consume.
But diets with sharp restriction calorie intake can also lead to sudden weight gain after withdrawal. Why? The body received a command: hunger. This means we need to accumulate fats in reserve. Therefore, all food is processed and goes to the “depot” - fat deposits. At the same time, you may faint from hunger. Processed carbohydrates are stored in fat reserves.
Studies show that if a person is on a low-calorie, low-fat diet, then the few kilograms lost with great difficulty come back, even if you continue to “sit” on this diet.
In addition, people who consume low amounts of fat are prone to obesity.
And observations of patients in the USA revealed a picture that a decrease in the amount of fat from 40% (which is considered normal) to 33% in the diet is accompanied by an increase in overweight people.
Remember that unsaturated fats are involved in metabolism. The protein: fat: carbohydrate ratio for an adult should be approximately 14%: 33%: 53%.
Conclusion: An increase in unsaturated fats in food while maintaining the same calorie content will not lead to weight gain, but will contribute to improved health through metabolism.
Thank you
The site provides background information for informational purposes only. Diagnosis and treatment of diseases must be carried out under the supervision of a specialist. All drugs have contraindications. Consultation with a specialist is required!
What kind of substances are lipids?
Lipids represent one of the groups organic compounds, having great value for living organisms. According to their chemical structure, all lipids are divided into simple and complex. Simple lipids are made up of alcohol and bile acids, while complex lipids contain other atoms or compounds. In general, lipids are of great importance to humans. These substances are included in a significant part of food products, are used in medicine and pharmacy, and play an important role in many industries. In a living organism, lipids in one form or another are part of all cells. From a nutritional point of view, it is a very important source of energy.
What is the difference between lipids and fats?
Basically, the term "lipids" comes from a Greek root meaning "fat", but there are still some differences between these definitions. Lipids are a larger group of substances, while fats refer to only certain types of lipids. A synonym for “fats” are “triglycerides,” which are obtained from a combination of glycerol alcohol and carboxylic acids. Both lipids in general and triglycerides in particular play a significant role in biological processes.Lipids in the human body
Lipids are part of almost all tissues of the body. Their molecules are present in any living cell, and without these substances life is simply impossible. There are many different lipids found in the human body. Each type or class of these compounds has its own functions. Many biological processes depend on the normal supply and formation of lipids. From a biochemical point of view, lipids take part in the following important processes:
- energy production by the body;
- cell division;
- transmission of nerve impulses;
- formation of blood components, hormones and other important substances;
- protection and fixation of some internal organs;
- cell division, respiration, etc.
Biological role of lipids in a living cell
Lipid molecules perform a huge number of functions not only on the scale of the entire organism, but also in each living cell individually. In essence, a cell is a structural unit of a living organism. It is where assimilation and synthesis occurs ( education) certain substances. Some of these substances go to maintaining the life of the cell itself, some to cell division, and some to the needs of other cells and tissues.In a living organism, lipids perform the following functions:
- energy;
- reserve;
- structural;
- transport;
- enzymatic;
- storing;
- signal;
- regulatory
Energy function
The energy function of lipids is reduced to their breakdown in the body, during which a large amount of energy is released. Living cells need this energy to maintain various processes ( respiration, growth, division, synthesis of new substances). Lipids enter the cell with blood flow and are deposited inside ( in the cytoplasm) in the form of small drops of fat. If necessary, these molecules are broken down and the cell receives energy.Reserve ( storing) function
The reserve function is closely related to the energy function. In the form of fats inside cells, energy can be stored “in reserve” and released as needed. Special cells – adipocytes – are responsible for the accumulation of fats. Most of their volume is occupied by a large drop of fat. It is adipocytes that make up adipose tissue in the body. The largest reserves of adipose tissue are located in the subcutaneous fat, the greater and lesser omentum ( in the abdominal cavity). During prolonged fasting, adipose tissue gradually breaks down, as lipid reserves are used to obtain energy.Also, adipose tissue deposited in subcutaneous fat provides thermal insulation. Tissues rich in lipids are generally poorer conductors of heat. This allows the body to maintain constant temperature body and not cool down or overheat so quickly in different conditions external environment.
Structural and barrier functions ( membrane lipids)
Lipids play a huge role in the structure of living cells. In the human body, these substances form a special double layer that forms the cell wall. Thereby living cell can perform its functions and regulate metabolism with the external environment. Lipids that form the cell membrane also help maintain the shape of the cell.Why do lipid monomers form a double layer ( bilayer)?
Monomers are called chemical substances (in this case – molecules), which are capable of combining to form more complex compounds. The cell wall consists of a double layer ( bilayer) lipids. Each molecule that forms this wall has two parts - hydrophobic ( not in contact with water) and hydrophilic ( in contact with water). The double layer is obtained due to the fact that the lipid molecules are deployed with hydrophilic parts inside and outside the cell. The hydrophobic parts practically touch, as they are located between the two layers. Other molecules may also be located in the depth of the lipid bilayer ( proteins, carbohydrates, complex molecular structures), which regulate the passage of substances through the cell wall.Transport function
The transport function of lipids is of secondary importance in the body. Only some connections do this. For example, lipoproteins, consisting of lipids and proteins, transport certain substances in the blood from one organ to another. However, this function is rarely isolated, without considering it to be the main one for these substances.Enzymatic function
In principle, lipids are not part of the enzymes involved in the breakdown of other substances. However, without lipids, organ cells will not be able to synthesize enzymes, the end product of vital activity. In addition, some lipids play a significant role in the absorption of dietary fats. Bile contains significant amounts of phospholipids and cholesterol. They neutralize excess pancreatic enzymes and prevent them from damaging intestinal cells. Dissolution also occurs in bile ( emulsification) exogenous lipids coming from food. Thus, lipids play a huge role in digestion and help in the work of other enzymes, although they are not enzymes themselves.Signal function
Some complex lipids perform a signaling function in the body. It consists of maintaining various processes. For example, glycolipids in nerve cells take part in the transmission of nerve impulses from one nerve cell to another. In addition, signals within the cell itself are of great importance. She needs to “recognize” substances entering the blood in order to transport them inside.Regulatory function
The regulatory function of lipids in the body is secondary. The lipids themselves in the blood have little effect on the course of various processes. However, they are part of other substances that are of great importance in the regulation of these processes. First of all, these are steroid hormones ( adrenal hormones and sex hormones). They play an important role in metabolism, growth and development of the body, reproductive function, affect the functioning of the immune system. Lipids are also part of prostaglandins. These substances are produced during inflammatory processes and affect certain processes in the nervous system ( for example, pain perception).Thus, lipids themselves do not perform a regulatory function, but their deficiency can affect many processes in the body.
Biochemistry of lipids and their relationship with other substances ( proteins, carbohydrates, ATP, nucleic acids, amino acids, steroids)
Lipid metabolism is closely related to the metabolism of other substances in the body. First of all, this connection can be traced in human nutrition. Any food consists of proteins, carbohydrates and lipids, which must enter the body in certain proportions. In this case, a person will receive both enough energy and enough structural elements. Otherwise ( for example, with a lack of lipids) proteins and carbohydrates will be broken down to produce energy.Also, lipids are, to one degree or another, associated with the metabolism of the following substances:
- Adenosine triphosphoric acid ( ATP). ATP is a unique unit of energy inside a cell. When lipids are broken down, part of the energy goes into the production of ATP molecules, and these molecules take part in all intracellular processes ( transport of substances, cell division, neutralization of toxins, etc.).
- Nucleic acids. Nucleic acids are structural elements of DNA and are found in the nuclei of living cells. The energy generated during the breakdown of fats is partially used for cell division. During division, new DNA chains are formed from nucleic acids.
- Amino acids. Amino acids are structural components of proteins. In combination with lipids, they form complex complexes, lipoproteins, responsible for the transport of substances in the body.
- Steroids. Steroids are a type of hormone that contains significant amounts of lipids. If lipids from food are poorly absorbed, the patient may experience problems with the endocrine system.
Digestion and absorption of lipids ( metabolism, metabolism)
Digestion and absorption of lipids is the first stage in the metabolism of these substances. The main part of lipids enters the body with food. IN oral cavity food is crushed and mixed with saliva. Next, the lump enters the stomach, where the chemical bonds are partially destroyed by hydrochloric acid. Also, some chemical bonds in lipids are destroyed by the enzyme lipase contained in saliva.Lipids are insoluble in water, so they are not immediately broken down by enzymes in the duodenum. First, the so-called emulsification of fats occurs. After this, the chemical bonds are broken down by lipase coming from the pancreas. In principle, each type of lipid now has its own enzyme responsible for the breakdown and absorption of this substance. For example, phospholipase breaks down phospholipids, cholesterol esterase breaks down cholesterol compounds, etc. All these enzymes are contained in varying quantities in pancreatic juice.
The split lipid fragments are absorbed individually by the cells of the small intestine. In general, the digestion of fats is a very difficult process, which is regulated by many hormones and hormone-like substances.
What is lipid emulsification?
Emulsification is the incomplete dissolution of fatty substances in water. In the bolus of food entering the duodenum, fats are contained in the form of large droplets. This prevents them from interacting with enzymes. During the emulsification process, large fat droplets are “crushed” into smaller droplets. As a result, the contact area between fat droplets and surrounding water-soluble substances increases, and lipid breakdown becomes possible.The process of emulsifying lipids into digestive system takes place in several stages:
- At the first stage, the liver produces bile, which will emulsify fats. It contains salts of cholesterol and phospholipids, which interact with lipids and contribute to their “crushing” into small droplets.
- Bile secreted from the liver accumulates in gallbladder. Here it is concentrated and released as needed.
- When consuming fatty foods, a signal is sent to the smooth muscles of the gallbladder to contract. As a result, a portion of bile is released through the bile ducts into the duodenum.
- In the duodenum, fats are actually emulsified and interact with pancreatic enzymes. Contractions in the walls of the small intestine facilitate this process by “mixing” the contents.
Enzymes for lipid breakdown
To digest each substance, the body has its own enzymes. Their task is to break chemical bonds between molecules ( or between atoms in molecules), to useful material could be normally absorbed by the body. Different enzymes are responsible for breaking down different lipids. Most of them are contained in the juice secreted by the pancreas.The following groups of enzymes are responsible for the breakdown of lipids:
- lipases;
- phospholipases;
- cholesterol esterase, etc.
What vitamins and hormones are involved in the regulation of lipid levels?
The levels of most lipids in human blood are relatively constant. It can fluctuate within certain limits. This depends on the biological processes occurring in the body itself, and on a number of external factors. Regulating blood lipid levels is complex biological process, in which many take part various organs and substances.The following substances play the greatest role in the absorption and maintenance of constant lipid levels:
- Enzymes. A number of pancreatic enzymes take part in the breakdown of lipids entering the body with food. With a lack of these enzymes, the level of lipids in the blood may decrease, since these substances simply will not be absorbed in the intestines.
- Bile acids and their salts. Bile contains bile acids and a number of their compounds, which contribute to the emulsification of lipids. Without these substances, normal absorption of lipids is also impossible.
- Vitamins. Vitamins have a complex strengthening effect on the body and also directly or indirectly affect lipid metabolism. For example, with a lack of vitamin A, cell regeneration in the mucous membranes deteriorates, and the digestion of substances in the intestines also slows down.
- Intracellular enzymes. The intestinal epithelial cells contain enzymes that, after absorption of fatty acids, convert them into transport forms and send them into the bloodstream.
- Hormones. A number of hormones affect metabolism in general. For example, high insulin levels can greatly affect blood lipid levels. That is why some standards have been revised for patients with diabetes. Thyroid hormones, glucocorticoid hormones, or norepinephrine can stimulate the breakdown of fat tissue to release energy.
Biosynthesis ( education) and hydrolysis ( decay) lipids in the body ( anabolism and catabolism)
Metabolism is the totality of metabolic processes in the body. All metabolic processes can be divided into catabolic and anabolic. Catabolic processes include the breakdown and breakdown of substances. In relation to lipids, this is characterized by their hydrolysis ( disintegrating into more simple substances ) V gastrointestinal tract. Anabolism combines biochemical reactions aimed at the formation of new, more complex substances.Lipid biosynthesis occurs in the following tissues and cells:
- Intestinal epithelial cells. Absorption of fatty acids, cholesterol and other lipids occurs in the intestinal wall. Immediately after this, new transport forms of lipids are formed in these same cells, which enter the venous blood and are sent to the liver.
- Liver cells. In liver cells, some of the transport forms of lipids will disintegrate, and new substances are synthesized from them. For example, cholesterol and phospholipid compounds are formed here, which are then excreted in bile and contribute to normal digestion.
- Cells of other organs. Some lipids travel with the blood to other organs and tissues. Depending on the cell type, lipids are converted into certain type connections. All cells, one way or another, synthesize lipids to form the cell wall ( lipid bilayer). In the adrenal glands and gonads, steroid hormones are synthesized from some lipids.
Resynthesis of lipids in the liver and other organs
Resynthesis is the process of formation of certain substances from simpler ones that were absorbed earlier. In the body, this process occurs during internal environment some cells. Resynthesis is necessary so that tissues and organs receive all the necessary types of lipids, and not just those consumed with food. Resynthesized lipids are called endogenous. The body spends energy on their formation.At the first stage, lipid resynthesis occurs in the intestinal walls. Here, fatty acids ingested from food are converted into transport forms that are transported through the blood to the liver and other organs. Part of the resynthesized lipids will be delivered to the tissues; from the other part, substances necessary for life will be formed ( lipoproteins, bile, hormones, etc.), the excess is converted into adipose tissue and stored “in reserve.”
Are lipids part of the brain?
Lipids are a very important component nerve cells not only in the brain, but throughout the entire nervous system. As you know, nerve cells control various processes in the body through the transmission of nerve impulses. In this case, all nerve pathways are “isolated” from each other so that the impulse comes to certain cells and does not affect other nerve pathways. This “isolation” is possible thanks to the myelin sheath of nerve cells. Myelin, which prevents the chaotic propagation of impulses, consists of approximately 75% lipids. As in cell membranes, here they form a double layer ( bilayer), which is wrapped several times around the nerve cell.The myelin sheath in the nervous system contains the following lipids:
- phospholipids;
- cholesterol;
- galactolipids;
- glycolipids.
Lipid hormones
Lipids play an important structural role, including being present in the structure of many hormones. Hormones that contain fatty acids are called steroid hormones. In the body they are produced by the gonads and adrenal glands. Some of them are also present in adipose tissue cells. Steroid hormones take part in the regulation of many vital processes. Their imbalance can affect body weight, the ability to conceive a child, the development of any inflammatory processes, and the functioning of the immune system. The key to normal production of steroid hormones is a balanced intake of lipids.Lipids are part of the following vital hormones:
- corticosteroids ( cortisol, aldosterone, hydrocortisone, etc.);
- male sex hormones - androgens ( androstenedione, dihydrotestosterone, etc.);
- female sex hormones - estrogens ( estriol, estradiol, etc.).
The role of lipids for skin and hair
Lipids are of great importance for the health of the skin and its appendages ( hair and nails). The skin contains so-called sebaceous glands, which release a certain amount of fat-rich secretion to the surface. This substance performs many useful functions.Lipids are important for hair and skin for the following reasons:
- a significant part of the hair substance consists of complex lipids;
- skin cells change rapidly, and lipids are important as an energy resource;
- secret ( secreted substance) sebaceous glands moisturize the skin;
- Thanks to fats, the firmness, elasticity and smoothness of the skin is maintained;
- a small amount of lipids on the surface of the hair gives it a healthy shine;
- the lipid layer on the surface of the skin protects it from the aggressive effects of external factors ( cold, sun rays, microbes on the surface of the skin, etc.).
Classification of lipids
In biology and chemistry, there are quite a few different classifications of lipids. The main one is chemical classification, according to which lipids are divided depending on their structure. From this point of view, all lipids can be divided into simple ones ( consisting only of oxygen, hydrogen and carbon atoms) and complex ( containing at least one atom of other elements). Each of these groups has corresponding subgroups. This classification is the most convenient, since it reflects not only the chemical structure of substances, but also partially determines the chemical properties. Biology and medicine have their own additional classifications that use other criteria.
Exogenous and endogenous lipids
All lipids in the human body can be divided into two large groups - exogenous and endogenous. The first group includes all substances that enter the body from the external environment. Largest quantity exogenous lipids enter the body with food, but there are other routes. For example, when using various cosmetics or medicines the body may also receive some lipids. Their action will be predominantly local.After entering the body, all exogenous lipids are broken down and absorbed by living cells. Here, from their structural components, other lipid compounds that the body needs will be formed. These lipids, synthesized by one's own cells, are called endogenous. They may have a completely different structure and function, but consist of the same “structural components” that entered the body with exogenous lipids. That is why, with a lack of certain types of fats in the diet, they can develop various diseases. Some components of complex lipids cannot be synthesized by the body independently, which affects the course of certain biological processes.
Fatty acid
Fatty acids are a class of organic compounds that are a structural part of lipids. Depending on which fatty acids are included in the lipid, the properties of this substance may change. For example, triglycerides, the most important source of energy for the human body, are derivatives of the alcohol glycerol and several fatty acids.In nature, fatty acids are found in a variety of substances - from petroleum to vegetable oils. They enter the human body mainly through food. Each acid is a structural component for specific cells, enzymes or compounds. Once absorbed, the body converts it and uses it in various biological processes.
Most important sources fatty acids for humans are:
- animal fats;
- vegetable fats;
- tropical oils ( citrus, palm, etc.);
- fats for the food industry ( margarine, etc.).
Saturated and unsaturated fatty acids
All fatty acids according to their chemical structure are divided into saturated and unsaturated. Saturated acids less beneficial for the body, and some of them are even harmful. This is explained by the fact that there are no double bonds in the molecule of these substances. These are chemically stable compounds and are less easily absorbed by the body. Currently, the connection between some saturated fatty acids and the development of atherosclerosis has been proven.Unsaturated fatty acids are divided into two large groups:
- Monounsaturated. These acids have one double bond in their structure and are therefore more active. It is believed that eating them can lower cholesterol levels and prevent the development of atherosclerosis. The greatest amount of monounsaturated fatty acids is found in a number of plants ( avocado, olives, pistachios, hazelnuts) and, accordingly, in oils obtained from these plants.
- Polyunsaturated. Polyunsaturated fatty acids have several double bonds in their structure. Distinctive feature of these substances is that human body unable to synthesize them. In other words, if the body does not receive polyunsaturated fatty acids from food, over time this will inevitably lead to certain disorders. Best sources These acids are seafood, soybean and flaxseed oil, sesame seeds, poppy seeds, wheat germ, etc.
Phospholipids
Phospholipids are complex lipids containing a phosphoric acid residue. These substances, along with cholesterol, are the main components of cell membranes. These substances also take part in the transport of other lipids in the body. From a medical point of view, phospholipids can also play a signaling role. For example, they are part of bile, as they promote emulsification ( dissolution) other fats. Depending on which substance is more in bile, cholesterol or phospholipids, you can determine the risk of developing cholelithiasis.Glycerol and triglycerides
In terms of its chemical structure, glycerol is not a lipid, but it is an important structural component of triglycerides. This is a group of lipids that play a huge role in the human body. Most important function These substances are the supply of energy. Triglycerides that enter the body with food are broken down into glycerol and fatty acids. As a result, a very large amount of energy is released, which goes to work the muscles ( skeletal muscles, cardiac muscles, etc.).Adipose tissue in the human body is represented mainly by triglycerides. Most of these substances, before being deposited in adipose tissue, undergo some chemical transformations in the liver.
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