Transport of lipids by blood and lymph. Mechanisms of transport and metabolism of fats (lipids) Transport forms of lipids in the blood biochemistry

Fats are hydrophobic, so there are special mechanisms for their transport in the blood. Free (non-esterified) fatty acids are transported by the blood in the form of complexes with albumin. Cholesterol, its esters, triacylglycerols, phospholipids are transported as lipoproteins.

Lipoproteins are molecular complexes composed of lipids and proteins.

Figure: 10.2. Lipoprotein structure

There are several classes of lipoproteins (LP), but all of them are united by the following features: 1) the surface layer of lipoproteins consists of phospholipids, free cholesterol and proteins; 2) each lipoprotein contains a special set of surface proteins - apolipoproteins (apo), which are designated by letters of the Latin alphabet (A, B, C); 3) the core (core) of lipoprotein consists of hydrophobic triacylglycerols, cholesterol esters (Fig. 10.2).

Apolipoproteins perform the following functions: 1) are structural components of lipoproteins; 2) participate in recognition and interaction with membrane receptors; 3) activate enzymes of lipoprotein metabolism.

Lipoproteins are classified into 4 main classes depending on density (determined by ultracentrifugation) and electrophoretic mobility (Table 10.1).

Table 10.1.

Classification of lipoproteins by separation method

The main parameters and composition of lipoproteins are presented in table. 10.2.

Chylomicrons (HM) - the largest particles. HM are synthesized in the intestinal mucosa and are involved in exogenous transport of food lipids to various tissues... The main lipid is triacylglycerols.

VLDLsynthesized in the liver. The main lipid is triacylglycerols... Main function - transport of endogenous lipids from the liver to peripheral tissues.

LDL is formed in the bloodstream from VLDL. Contain a lot cholesterol (the main cholesterol transporter) which is transported into peripheral tissues.

HDLare formed in the liver, contain a lot of phospholipids and proteins; in these drugs, the sheath components prevail over the core.

Table 10.2

Lipoprotein composition

TG - triacylglycerols, PL - phospholipids. CS - cholesterol

Distinguish between exogenous (transport of food lipids) and endogenous (transport of lipids synthesized in the body) transport.

Exogenous transport. The products of lipid digestion are absorbed into the cells of the intestinal mucosa as part of micelles. Fatty acids with the number of carbon atoms<12 всасываются в кровь и по воротной вене транспортируются в печень. Длинноцепочечные жирные кислоты (С >12) in intestinal cells are re-esterified into triacylglycerols, which are similar in composition to dietary fats. The resulting triacylglycerols together with phospholipids, cholesterol and proteins (2%) form chylomicrons. Chylomicrons contain apoprotein B48 and apoA.

Figure: 10.3. Exogenous transport of lipids (according to Murray R. et al., 2004)

Chylomicrons enter the lymph. In the blood, they are found with HDL particles containing apoE and apoC. Chylomicrons donate apoA to HDL particles, and in return acquire apoE and apoC. One of the group C apolipoproteins, apoCII, serves as an activator of the lipoprotein lipase (LPL) enzyme. This enzyme is synthesized and secreted by adipose and muscle tissues, breast cells. The secreted enzyme attaches to the plasma membrane of the endothelial cells of the capillaries of those tissues where it was synthesized. ApoCII on the surface of the CM activates LPL. It hydrolyzes triacylglycerols in the HM to glycerol and fatty acids. These fatty acids either enter the cells of adipose and muscle tissue, or combine with plasma albumin. As a result of LPL action, chylomicrons sharply decrease in size and they are called remnants (remnants). HM remnants are captured by the liver via the receptor pathway (Fig. 10.3).

Endogenous transport. In liver cells, triacylglycerols and phospholipids, which are characteristic of this organism, are resynthesized. They are included in VLDL. VLDLP contains apoB100 and apoC. This is the main transport form of triacylglycerols. Another class of lipoproteins formed in the liver - HDL - includes cholesterol, phospholipids, apoA. These particles are flat and are called nascent HDL. (There are no hydrophobic molecules in their core.) These HDLs play an important role in the reverse transport of cholesterol from peripheral tissue cells to the liver.

In the capillaries of adipose and muscle tissues, VLDL apoCII activates LPL, which catalyzes the hydrolysis of VLDL triacylglycerols and converts them into IDDs (intermediate density lipoproteins). Under the action of the circulating hepatic triacylglycerolipase synthesized in the liver, IDPs also lose some of the triacylglycerols and turn into LDL. Cholesterol becomes the main lipid of LDL, which is transported as part of LDL to the cells of all tissues. Therefore, LDL is formed directly in the vascular bed (Fig. 10.4).

Figure: 10.4. Endogenous transport of lipids (according to Murray R. et al., 2004)

So, as a result of exogenous and endogenous transport, fatty acids and glycerol are released in the capillaries of adipose and muscle tissues. Fatty acids bind to albumin and are transported to consumer tissues.

I approve

Head department prof., d.m.s.

Meshchaninov V.N.

_____''_____________ 2005

Lecture number 12 Topic: Digestion and absorption of lipids. Transport of lipids in the body. Lipoprotein metabolism. Dyslipoproteinemia.

Faculties: medical and preventive, medical and preventive, pediatric.

Lipids is a structurally diverse group of organic substances, which are united by a common property - solubility in non-polar solvents.

Lipid classification

Lipids, according to their ability to hydrolyze in an alkaline medium with the formation of soaps, are divided into saponifiable (contain fatty acids) and unsaponifiable (one-component).

Saponified lipids mainly contain alcohols glycerol (glycerolipids) or sphingosine (sphingolipids), according to the number of components, they are divided into simple (consist of 2 classes of compounds) and complex (consist of 3 or more classes).

Simple lipids include:

1) wax (ester of a higher monohydric alcohol and fatty acid);

2) triacylglycerides, diacylglycerides, monoacylglycerides (ester of glycerol and fatty acids). A person weighing 70 kg of TG has about 10 kg.

3) ceramides (ester of sphingosine and fatty acid C18-26) - form the basis of sphingolipids;

Complex lipids include:

1) phospholipids (contain phosphoric acid):

a) phospholipids (an ester of glycerol and 2 fatty acids, contains phosphoric acid and an amino alcohol) - phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol;

b) cardiolipins (2 phosphatidic acids linked through glycerol);

c) plasmalogens (ester of glycerol and fatty acid, contains unsaturated monohydric higher alcohol, phosphoric acid and amino alcohol) - phosphatidal ethanolamines, phosphatidalserines, phosphatidalcholines;

d) sphingomyelins (ester of sphingosine and fatty acid C18-26, contains phosphoric acid and amino alcohol - choline);

2) glycolipids (contain carbohydrate):

a) cerebrosides (ester of sphingosine and fatty acid C18-26, contains hexose: glucose or galactose);

b) sulfatides (ester of sphingosine and fatty acid C18-26, contains hexose (glucose or galactose) to which sulfuric acid is attached in position 3). Much in white matter;

c) gangliosides (ester of sphingosine and fatty acid C18-26, contains an oligosaccharide from hexoses and sialic acids). Found in ganglion cells;

Unsaponifiable lipids include steroids, fatty acids (a structural component of saponifiable lipids), vitamins A, D, E, K, and terpenes (hydrocarbons, alcohols, aldehydes and ketones with several isoprene units).

Biological functions of lipids

In the body, lipids perform a variety of functions:

Structural... Complex lipids and cholesterol are amphiphilic; they form all cell membranes; phospholipids line the surface of the alveoli, form a shell of lipoproteins. Sphingomyelins, plasmalogens, glycolipids form myelin sheaths and other membranes of nerve tissues.

Energy... In the body, up to 33% of all ATP energy is formed due to lipid oxidation;

Antioxidant... Vitamins A, D, E, K prevent SRO;

Storing... Triacylglycerides are a form of storage of fatty acids;

Protective... Triacylglycerides in adipose tissue provide thermal insulation and mechanical protection of tissues. Waxes form a protective lubricant on human skin;

Regulatory... Phosphotidylinositols are intracellular mediators in the action of hormones (inositol triphosphate system). Eicosanoids are formed from polyunsaturated fatty acids (leukotrienes, thromboxanes, prostaglandins), substances that regulate immunogenesis, hemostasis, nonspecific resistance of the body, inflammatory, allergic, proliferative reactions. From cholesterol, steroid hormones are formed: sex and corticoids;

Vitamin D and bile acids are synthesized from cholesterol;

Digestive... Bile acids, phospholipids, cholesterol provide emulsification and lipid absorption;

Information... Gangliosides provide intercellular contacts.

The source of lipids in the body is synthetic processes and food. Some lipids in the body are not synthesized (polyunsaturated fatty acids - vitamin F, vitamins A, D, E, K), they are irreplaceable and come only with food.

Principles of lipid regulation in nutrition

A person needs to eat 80-100 g of lipids per day, of which 25-30 g of vegetable oil, 30-50 g of butter and 20-30 g of animal fat. Vegetable oils contain many essential polyene (linoleic up to 60%, linolenic) fatty acids, phospholipids (removed during refining). Butter contains many vitamins A, D, E. Food lipids contain mainly triglycerides (90%). A day with food comes about 1 g of phospholipids, 0.3-0.5 g of cholesterol, mainly in the form of esters.

The requirement for dietary lipids depends on age. For infants, lipids are the main source of energy, and for adults, glucose. Newborns 1 to 2 weeks old require lipids 1.5 g / kg, children - 1 g / kg, adults - 0.8 g / kg, elderly - 0.5 g / kg. The need for lipids increases in the cold, during physical exertion, during the recovery period and during pregnancy.

All natural lipids are well digested, oils are absorbed better than fats. With a mixed diet, butter is absorbed by 93-98%, pork fat - by 96-98%, beef fat - by 80-94%, sunflower oil - by 86-90%. Prolonged heat treatment (\u003e 30 min) destroys beneficial lipids, thus forming toxic products of fatty acid oxidation and carcinogenic substances.

With insufficient intake of lipids from food, immunity decreases, the production of steroid hormones decreases, and sexual function is impaired. With a deficiency of linoleic acid, vascular thrombosis develops and the risk of cancer increases. With an excess of lipids in food, atherosclerosis develops and the risk of breast and colon cancer increases.

Digestion and absorption of lipids

Digestion it is the hydrolysis of nutrients to their assimilable forms.

Only 40-50% of dietary lipids are completely broken down, and from 3% to 10% of dietary lipids can be absorbed unchanged.

Since lipids are insoluble in water, their digestion and absorption has its own characteristics and proceeds in several stages:

1) Lipids of solid food under mechanical action and under the influence of surfactants of bile are mixed with digestive juices to form an emulsion (oil in water). The formation of an emulsion is necessary to increase the area of \u200b\u200baction of enzymes. they only work in the aqueous phase. Lipids of liquid food (milk, broth, etc.) enter the body immediately in the form of an emulsion;

2) Under the action of lipases of digestive juices, the lipids of the emulsion are hydrolyzed to form water-soluble substances and simpler lipids;

3) The water-soluble substances released from the emulsion are absorbed and enter the blood. The simpler lipids isolated from the emulsion combine with bile components to form micelles;

4) Micelles ensure lipid absorption into intestinal endothelial cells.

Oral cavity

In the oral cavity, solid food is mechanically ground and wetted with saliva (pH \u003d 6.8). Here, the hydrolysis of triglycerides with short and medium fatty acids begins, which come with liquid food in the form of an emulsion. Hydrolysis is carried out by lingual triglyceride lipase ("lipase of the tongue", THL), which is secreted by the Ebner glands located on the dorsal surface of the tongue.

Stomach

Since the "lipase of the tongue" acts in the range of 2-7.5 pH, it can function in the stomach for 1-2 hours, breaking down up to 30% triglycerides with short fatty acids. In infants and young children, it actively hydrolyzes milk TGs, which contain mainly fatty acids with short and medium chain lengths (4-12 C). In adults, the contribution of "tongue lipase" to the digestion of TG is insignificant.

In the main cells of the stomach, gastric lipase , which is active at a neutral pH, characteristic of the gastric juice of infants and young children, and inactive in adults (pH of gastric juice ~ 1.5). This lipase hydrolyzes TG by cleaving mainly fatty acids at the third carbon atom of glycerol. The FA and MG formed in the stomach are further involved in the emulsification of lipids in the duodenum.

Small intestine

The main process of lipid digestion takes place in the small intestine.

1. Emulsification lipids (mixing of lipids with water) occurs in the small intestine under the action of bile. Bile is synthesized in the liver, concentrated in the gallbladder and, after taking fatty foods, is released into the lumen of the duodenum (500-1500 ml / day).

Bile it is a viscous yellow-green liquid, has a pH \u003d 7.3-8.0, contains H 2 O - 87-97%, organic matter (bile acids - 310 mmol / l (10.3-91.4 g / l), fatty acids - 1.4-3.2 g / l, bile pigments - 3.2 mmol / l (5.3-9.8 g / l), cholesterol - 25 mmol / l (0.6-2.6) g / l, phospholipids - 8 mmol / l) and mineral components (sodium 130-145 mmol / l, chlorine 75-100 mmol / l, HCO 3 - 10-28 mmol / l, potassium 5-9 mmol / l). Violation of the ratio of the components of bile leads to the formation of stones.

Bile acids (derivatives of cholanic acid) are synthesized in the liver from cholesterol (cholic and chenodeoxycholic acids) and are formed in the intestines (deoxycholic, lithocholic, etc. about 20) from cholic and chenodeoxycholic acids under the action of microorganisms.

In bile, bile acids are present mainly in the form of conjugates with glycine (66-80%) and taurine (20-34%), forming paired bile acids: taurocholic, glycocholic, etc.

Salts of bile acids, soaps, phospholipids, proteins and the alkaline medium of bile act as detergents (surfactants), they reduce the surface tension of lipid droplets, as a result of which large droplets disintegrate into many small ones, i.e. emulsification occurs. Emulsification is also facilitated by intestinal peristalsis and released, during the interaction of chyme and bicarbonates, CO 2: H + + HCO 3 - → H 2 CO 3 → H 2 O + CO 2.

2. Hydrolysis triglycerides carries out pancreatic lipase. Its optimum pH \u003d 8, it hydrolyzes TG mainly in positions 1 and 3, with the formation of 2 free fatty acids and 2-monoacylglycerol (2-MG). 2-MG is a good emulsifier. 28% of 2-MG is converted to 1-MG by the action of isomerase. Most of 1-MG is hydrolyzed by pancreatic lipase to glycerol and fatty acid.

In the pancreas, pancreatic lipase is synthesized together with the protein colipase. Colipase is formed in an inactive form and is activated in the intestine by trypsin by partial proteolysis. With its hydrophobic domain, colipase binds to the surface of the lipid droplet, while its hydrophilic domain contributes to the maximum approach of the active center of pancreatic lipase to TG, which accelerates their hydrolysis.

3. Hydrolysis lecithin occurs with the participation of phospholipases (PL): A1, A2, C, D and lysophospholipase (lysoPL).

As a result of the action of these four enzymes, phospholipids are cleaved to free fatty acids, glycerol, phosphoric acid and aminoalcohol or its analogue, for example, the amino acid serine, however, part of the phospholipids is cleaved with the participation of phospholipase A2 only to lysophospholipids and in this form can enter the intestinal wall.

PL A 2 is activated by partial proteolysis with trypsin and hydrolyzes lecithin to lysolecithin. Lysolecithin is a good emulsifier. LysoPL hydrolyzes part of lysolecithin to glycerophosphocholine; the rest of the phospholipids are not hydrolyzed.

4. Hydrolysis cholesterol esters to cholesterol and fatty acids is carried out by cholesterol esterase, an enzyme of the pancreas and intestinal juice.

The transfer of membrane lipids from the place of their synthesis to the place of destination is carried out using two processes: 1) transmembrane flip-flop transition; 2) intramembrane transport. Flip flop speed data has been discussed in connection with membrane asymmetry. The rate of flip-flop transition of phospholipids is especially high for those membranes in which lipid biosynthesis occurs; its characteristic time is on the order of several minutes. There is evidence that this process is carried out with the participation of proteins and, possibly, requires ATP hydrolysis. It has also been shown that cholesterol is capable of rapid spontaneous flip-flop transition. Consequently, transport across the membrane of the endoplasmic reticulum from the cytosol to the lumen occurs rather quickly.

Several processes are involved in the transport of lipids from one cell membrane to another. In different cases, the most important may be one of them.

1. Spontaneous transfer of lipids by diffusion of monomeric lipid units through the aqueous phase.

2. Diffusion of lipids through permanent or temporary junctions of two contacting membranes.

3. Transport with the participation of proteins, catalyzed by either proteins that facilitate the release of lipids from the donor membrane, or lipid-binding proteins.

4. Transport with the participation of vesicles, in which lipids, like membrane proteins, are transported during continuous budding and fusion with the membranes of intracellular vesicles. This process can be volatile.

Let us first consider what is known about the spontaneous diffusion of membrane lipids between membranes. Numerous studies show that lipids can spontaneously move between monolamellar vesicles or between phospholipid vesicles and biomembranes. In most cases, this involves desorption of monomeric lipids from the surface of the donor membrane and free diffusion through the aqueous medium to the acceptor membrane. The limiting step (at least with an excess of acceptor membranes) is the release of lipids from the donor membrane. Under these conditions, the characteristic transfer time depends on the value of the free energy of desorption. It is clear that less water-soluble lipids (i.e., lipids with a low critical micelle concentration) must overcome a higher energy barrier during desorption, and therefore, their transfer must be slower. The transfer rate depends not only on the hydrophobicity of the transferred lipnd, but also on the composition and physical state of the donor bilayer.

For example, the ganglioside GM b, being in phosphatidylcholine vesicles, exists in a monodisperse state. Due to the presence of hydrophilic polar groups, it does not perform flip-flop transitions across the vesicle membrane, but the characteristic time of its transfer by vesicles is about 40 h at 45 ° C. On the contrary, neutral gangliosides devoid of sialic acid residues (for example, asialo-GMi) form a gel-like cluster in vesicles, and the characteristic time of their transfer is about 500 hours. A mixture of cholesterol and phospholipids in vesicles also forms complex phases, and this can affect the kinetics transfer of cholesterol. The stabilization of cholesterol in the membrane could occur due to favorable interactions with specific phospholipids, for example, with sphingomyelin.

The transfer of newly synthesized cholesterol from the endoplasmic reticulum to the plasma membrane is carried out in just 10 minutes. The process is influenced by agents that block bioenergetic reactions in the cell, such as cyanide. These and other data indicate that intracellular cholesterol transport is an energy-dependent process and proceeds with the participation of vesicles. In principle, it can outweigh any spontaneous transference. However, there is no consensus on this score. A serious problem is that estimates of the proportion of cholesterol present in the plasma membrane of the total amount in the cell vary greatly (from 25 to 95%). At first glance, it seems that the amount of cholesterol entering and leaving some cells can be estimated using data on the rate of spontaneous diffusion of monomers; however, it is unclear whether the spontaneous transfer mechanism and the indicated rates are suitable in this case.

The characteristic time of transfer of phospholipids from phospholipid vesicles is much longer than that of cholesterol. For example, for dipalmitoylphosphatidylcholine, it is 83 hours at 37 ° in the case of dimyristoylphosphatidylcholine vesicles. The rate of transfer of phospholipids by this mechanism is too low to correspond to the actual rates of intermembrane transport.

From a biological point of view, the most important physicochemical properties of lipids are opposite in properties to carbohydrates. Their molecules are fat-soluble, large, and have a relatively low content of oxygen atoms.

Lipids are a slow energy substrate. Due to their low solubility in water, they are not able to reach a high concentration in the blood, and therefore they cannot be an energy substrate for tissues.

There are quite a lot of lipids. First, due to the low number of oxygen atoms, the free energy of lipids is quite high. Secondly, due to their hydrophobicity, they can form large droplets that fill almost the entire cell.

Lipids are an important plastic material. They can form a hydrophobic membrane that limits the cell from the surrounding aqueous solution. For this reason, they are the basis for biological membranes.

Subcutaneous adipose tissue is a heat insulator. Lipid deposition is an important mechanical function.

The main lipids of the human body are cholesterol, phospholipids, triglycerides.

Fatty acids and triglycerides mainly function as energy substrates. Cholesterol and phospholipids are used for other purposes - for the formation of biologically active substances and membranes.

Triglyceride Uses:

Deposition in adipose tissue, catabolism - membrane building.

Sources of intake of triglycerides:

They come with food and are mobilized from adipose tissue.

Formation from carbohydrates and proteins. With an increased intake of substrates, they are converted into triglycerides in the liver, and are transferred to the adipose tissue by the blood, where they remain.

The main form of lipid deposition in adipose tissue is triglycerides.

Fatty acids are the main energy substrate supplied to cells from adipose tissue. This is due to the fact that fatty acids penetrate better through cell membranes.

The faster energy substrate is ketone bodies. Ketone bodies are formed in the liver. Ketone bodies can be used with fast-metabolizing tissues. But for ketone bodies to completely oxidize, carbohydrate oxidation products are needed. Therefore, in the presence of disorders of carbohydrate catabolism, ketone bodies accumulate in the blood.

1

TRANSPORTATION OF LIPIDS

1.EXOGENOUS
2.Endogenous
2

Fats are hydrophobic, therefore
there are special mechanisms
their transport in the blood. Free
(unesterified) fatty
acids are carried in the blood as
complexes with albumin.
Cholesterol, its esters,
triacylglycerols, phospholipids
transported as part
lipoproteins.
3

Lipoproteins are subdivided into 4
main classes depending on density
(defined by
ultracentrifugation) and
electrophoretic mobility:
1. XM;
2. VLDL;
3. LDL;
4. HDL.
4

Distinguish between exo- and endogenous transport
lipids. Transport is exogenous.
lipids taken with food, and to
endogenous - the movement of lipids,
synthesized in the body. Exists
several types of drugs, but they all have a similar
structure - hydrophobic core and hydrophilic
layer on the surface. Hydrophilic layer
formed by proteins called
apoproteins, and amphiphilic molecules
lipids - phospholipids and cholesterol.
The hydrophilic groups of these molecules are reversed
to the aqueous phase, and hydrophobic to the core, in
which contains the transported lipids.
5

Lipoprotein structure

6

Functions of apoproteins:
· Form the structure of lipoproteins;
Interact with receptors on
cell surface, determining what
this type will be captured by the tissues
lipoproteins;
Are enzymes or activators
enzymes acting on
lipoproteins.
7

With exogenous transport
TAG resynthesized in enterocytes together
with phospholipids, cholesterol and proteins
form HM, and in this form are secreted
first into the lymph, and then into the blood. IN
lymph and blood from HDL to HM are transferred
apoproteins E (apo E) and C-II (apo C-II), such
In this way, HMs turn into "mature" ones.
Getting into the circulatory system, HM
are quickly catabolized and disappear
during few hours. Time
destruction of CM depends on the hydrolysis of TAG under
the action of lipoprotein lipase (LPL).
8

STRUCTURE OF CHILOMICRON

9

LPL is synthesized and secreted by adipose and
muscle tissue, milk cells
glands. The secreted LPL binds to
endothelial cell surface
capillaries of those tissues where it is
synthesized. The regulation of secretion has
tissue specificity. In adipose tissue
LPL synthesis is stimulated by insulin. Topics
this ensures the intake of fatty
acids for synthesis and storage in the form of TAG. When
diabetes mellitus when there is a deficiency
insulin, LPL levels decrease. IN
as a result, a large
the number of drugs. In the muscles where LPL is involved in
supply of fatty acids for oxidation between
meals, insulin suppresses
the formation of this enzyme.
10

Two factors are distinguished on the surface of the XM,
necessary for LPL activity - apoCII and phospholipids. ApoC-II activates
this enzyme, and phospholipids are involved
in binding the enzyme to the surface
HM. As a result of the LPL's action on
TAG molecules are formed fatty
acids and glycerol. The bulk
fatty acids penetrate into tissues where
can be deposited as TAG
(adipose tissue) or used in
as a source of energy (muscle).
Glycerol is transported by blood to
the liver, where during the absorption period it can
be used for the synthesis of fats. eleven

As a result of LPL action, the amount
neutral fat in HM is reduced by 90%,
reduce particle size, apoC-II
transferred back to HDL. The resulting
particles are called residual HM
(with remnants). They contain FL, HS,
fat-soluble vitamins, apoB-48 and apoE.
Residual HM are captured by hepatocytes,
which have receptors
interacting with these apoproteins.
Under the action of lysosomal enzymes, proteins and
lipids are hydrolyzed and then
disposed of. Fat-soluble vitamins and
exogenous cholesterol is used in the liver or
transported to other organs.
12

With endogenous transport
TAG and FL resynthesized in the liver
are included in VLDL, which includes
apoB100 and apoC. VLDL are
main transport form for
endogenous TAGs. Once in the blood, VLDL
receive apoC-II and apoE from HDL and
exposed to LPL. During this
process VLDLP first turn into
LDPP, and then in LDL. Major lipid
LDL becomes cholesterol, which is in their composition
is transferred to the cells of all tissues.
Fatty substances formed during hydrolysis
acids enter tissues, and glycerol enters blood
transported to the liver, where it can again
used for the synthesis of TAG.
13

TYPES OF LIPOPROTEINS

Types of lipoproteins
Chilo microns
(Xm)
VLDL
Functions
Transport
exogenous
lipids
Transport
endogenous
lipids
A place
education
Epithelium
thin
intestines
Density, g / ml
LDPP
Intermediate
the form
LDL
HDL
Transport
cholesterol in
fabrics
Deleting
excess
cholesterol
Liver cells Blood
Blood (from
VLDL and
LDPP)
Liver cells
0,92-0,98
0,96-1,00
1,00-1,06
1,06-1,21
Particle diameter,
nm
>120
30-100
21-100
7-15
The main
apoproteins
B-48
C-II
E
B-100
C-II
E
B-100
A-I
C-II
E
B-100
E
14

COMPOSITION OF LIPOPROTEINS

composition of lipoproteins,%
lipoprotein
TAG X + EC apoproteins FL
XM
85
5
2
3
VLDL
55
17
10
18
LDPP
226
38
11
23
LDL
7
50
22
21
HDL
3
20
50
27
15

Causes of atherosclerosis

- lack of intake of vegetable
fibers, antioxidants (vitamins E, C, beta-carotenoids, flavonoids, thymol
compounds, etc.), potassium, magnesium, chromium;
- excess in the diet of oxidized fats,
oxidized cholesterol and the like;
- belonging to the male sex;
- increasing the calorie content of the diet;
- abdominal obesity;
- consumption of excess amounts
refined products;
- smoking;
- sharp changes in diet;
- soft drinking water;
- increased consumption of processed
milk protein - casein;
-environmental pollution.
16

Development of atherosclerosis
Healthy
artery
Fatty Transitional
Atheroma
streak damage
Action of risk factors
Mature plaque rupture
Thrombosis
plaque
Ischemic heart disease
17

Structure and function of complex lipids

18

Acylglycerols

Acylglycerols (acylglycerols,
neutral fats) are complex
ethers of trihydric alcohol glycerol
and higher fatty acids. They are referred to
universal substances of all
unicellular and multicellular
organisms. In the glycerol molecule
can be esterified like everyone else
three hydroxyl groups and one.
19

Triacylglycerols (TAGs)

Triacylglycerols account for 11
kg from the mass of a person. Simple TAG
consist of three acid radicals,
belonging to one acid
(tripalmitin, triolein). Part
mixed TAGs include the remains of different
fatty acids.
20

Simple triacylglycerols

The composition includes the remains of the same LCD,
for example, triacylglycerol.
21

Complex triacylglycerols

The composition includes the remains of various FA,
for example, 1-palmitoyl-2-stearoyl-3oleylglycerol.
22

23

Diol lipids

In mammals, in seeds
small amount of plants
there are ethers of alcohols
or esters of LC and diatomic
ethanediol alcohol (ethylene glycol).
Present in regenerating tissues
animals and plants in maturing
seeds.
24

25

Lipoproteins

Complex compounds with proteins
Are a part of cell membranes
Are a transport form
blood lipids: lipid drop
surrounded by apoproteins
(supramolecular complexes).
Representatives: HDL, LDL, VLDL,
chylomicrons and others.
26

Phospholipids

are esters of various
polyhydric and amino alcohols with fatty
acids and phosphoric acid
the main components of cell membranes,
are found in blood plasma
functions: receptor, barrier, transport.
Never stocked up in large quantities
A) PHOSPHOGLYCERINS (GLYCEROPHOSPHOLIPIDS)
most well studied. Contain residues
glycerin, fatty acids, phosphoric acid,
amino alcohols: colamine, choline, serine, etc.
The main intermediate product is phosphatide
acid
27

X \u003d -CH2-CH2-N (+) (CH3) 3 - phosphatidylcholines
X \u003d -CH2-CH2-NH2
- phosphatidylethanolamines
X \u003d -CH2-CH (NH2) COOH - phosphatidylserines
X \u003d -CH2-CH (OH) -CH2-OH - phosphatidylglycerols
X \u003d sugar
- phosphatidyl sugar
28
(otherwise - glycolipids)

29

X \u003d cyclic hexahedral alcohol inositol Called phosphatidylinositols or inositol phosphatides

30

diphosphatidylglycerol

31

B) Lipids that do not contain glycerin instead of glycerin contains

(sphingophosphatides)
32

acylation of sphingosine -
by amino group
33

Sphingomyelin
contains sphingosine in the form of ceramide,
combined with the remainder of choline through
phosphoric acid
(similar to glycerophospholipids)
34

Glycolipids

GLYCOSPHINGOLIPIDS differ from
phospholipids:
- no phosphoric acid residue
- there is a monosaccharide or its derivative
In the nervous tissue form
white and gray matter.
Depending on the length and structure of the carbohydrate portion:
Cerebrosides - mono or oligosaccharide residues
(more often glucose or galactose) associated
glycosidic linkage to the third hydroxyl of sphingosine
(without the participation of phosphoric acid).
Gangliosides - long chains of carbohydrate molecules
(complex branched oligosaccharide, in its composition Nacetyl-neuraminic or sialic acids).
35

GENERAL PROPERTIES
glyco- and phospholipids
amphotericity - the ability to
dissociation by acid and
alkaline types;
the formation of bipolar ions;
thanks to this glyco- and
phospholipids easily form
various complexes with proteins;
protein-lipid complexes
form the basis of cellular
membranes.
36

Steroids - high molecular weight
polycyclic alcohols
37

Fatty acid esters - sterols

H3C
18
11
19
2
3
BUT
1
4
CH3
10
5
12
21
CH3
13
22
20
17
H3C
23
24
16
26
25
CH3
CH3
CH3
27
CH3
14
9
6
CH3
CH3
CH3
8
7
Cholesterol
BUT
Ergosterol
The role of cholesterol: its derivatives form
biologically active substances, bile acids,
group D vitamins, steroid hormones.
The bulk of cholesterol (70-80%) is formed in
liver from fatty acids (mainly
saturated) and acetic acid (decomposition product
carbohydrates). Some of the cholesterol comes from food. 38

Bile acids

These are derivatives of cholanic acid or
C24 steroids. They are the main
cholesterol metabolism products,
synthesized in hepatocytes, excreted
and accumulate in the gallbladder as part of
bile in the form of conjugates with amino acids -
glycine and taurine, then enter the duodenum. By synthesizing fatty
acid cholesterol is excreted from the body.
39

40

The nature of the food affects the ratio
conjugates with glycine or taurine.
Food rich in carbohydrates increases
the percentage of glycine, and
protein - taurine conjugates.
Bile acids carry out
emulsification of fats coming from
food, and activate lipase
pancreatic juice.
41

Steroid Glycosides

Steroid glycosides include
cardiac glycosides. In small
doses, they have a cardiotonic
action - stimulate work
heart muscle, enhance
heartbeats, slow them down
frequency. Capable of accumulating in
body and with increasing dose
act as cardiotoxins,
causing cardiac arrest.
42

Saponins

Saponins are a separate group
steroid terpenoid glycosides, aqueous
solutions of which form a soapy foam.
They are isolated from the lily families,
amaryllis, marine organisms.
The carbohydrate component of saponins includes from
1 to 6 monosaccharide residues, and aglycone
has a common name - sapogenin. Saponins
cause hemolysis of erythrocytes, because possess
surfactant properties and
capable of destroying biological membranes.