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Lipids- fat-like organic compounds, insoluble in water, but highly soluble in non-polar solvents (ether, gasoline, benzene, chloroform, etc.). Lipids belong to the simplest biological molecules. Chemically, most lipids are esters of higher carboxylic acids and a number of alcohols. The most famous among them fats. Each fat molecule is formed by a molecule of the trihydric alcohol glycerol and ester bonds of three molecules of higher carboxylic acids attached to it. According to the accepted nomenclature, fats are called triacylglycerols.

When fats are hydrolyzed (i.e. split due to the introduction of H + and OH - into ester bonds), they break down into glycerol and free higher carboxylic acids, each of which contains an even number of carbon atoms.

Carbon atoms in the molecules of higher carboxylic acids can be connected to each other by both single and double bonds. Among the limiting (saturated) higher carboxylic acids, the composition of fats most often includes:

• palmitic CH 3 - (CH 2) 14 - COOH or C 15 H 31 COOH;
• stearic CH 3 - (CH 2) 16 - COOH or C 17 H 35 COOH;
• arachidic CH 3 - (CH 2) 18 - COOH or C 19 H 39 COOH;

among the unlimited:

• oleic CH 3 - (CH 2) 7 - CH \u003d CH - (CH 2) 7 - COOH or C 17 H 33 COOH;
• linoleic CH 3 - (CH 2) 4 - CH \u003d CH - CH 2 - CH - (CH 2) 7 - COOH or C 17 H 31 COOH;
• linolenic CH 3 - CH 2 - CH \u003d CH - CH 2 - CH \u003d CH - CH 2 - CH \u003d CH - (CH 2) 7 - COOH or C 17 H 29 COOH.

The degree of unsaturation and the chain length of higher carboxylic acids (i.e. the number of carbon atoms) determines the physical properties of a particular fat.

Fats containing short and unsaturated carbon chains in fatty acid residues have a low melting point. At room temperature, these are liquids (oils) or greasy substances. Conversely, fats with long and saturated chains of higher carboxylic acids are solids at room temperature. That is why hydrogenation (saturation of acid chains with hydrogen atoms in double bonds) turns liquid peanut butter, for example, into a homogeneous, spreadable peanut butter, and sunflower oil into margarine. Animals living in cold climates, such as fish in the Arctic seas, usually contain more unsaturated triacylglycerols than those living in southern latitudes. For this reason, their body remains flexible even at low temperatures.

Distinguish:

Phospholipids- amphiphilic compounds, i.e., they have polar heads and non-polar tails. The groups that form the polar head are hydrophilic (soluble in water), while the non-polar tail groups are hydrophobic (insoluble in water).

The dual nature of these lipids determines their key role in the organization of biological membranes.

Wax- esters of monohydric (with one hydroxyl group) macromolecular (having a long carbon skeleton) alcohols and higher carboxylic acids.

Another group of lipids are steroids. These substances are built on the basis of cholesterol alcohol. Steroids are very poorly soluble in water and do not contain higher carboxylic acids.

These include bile acids, cholesterol, sex hormones, vitamin D, etc.

close to steroids terpenes(growth substances of plants - gibberellins; phytol, which is part of chlorophyll, carotenoids - photosynthetic pigments; essential oils of plants - menthol, camphor, etc.).

Lipids can form complexes with other biological molecules.

Lipoproteins- complex formations containing triacylglycerols, cholesterol and proteins, the latter not having covalent bonds with lipids.

Glycolipids- this is a group of lipids built on the basis of sphingosine alcohol and containing, in addition to the remainder of higher carboxylic acids, one or more sugar molecules (most often glucose or galactose).

Functions of lipids

Structural. Phospholipids together with proteins form biological membranes. The membranes also contain sterols.

Energy. When 1 g of fat is oxidized, 38.9 kJ of energy is released, which goes to the formation of ATP. In the form of lipids, a significant part of the body's energy reserves are stored, which are consumed when there is a lack of nutrients. Hibernating animals and plants accumulate fats and oils and use them to maintain life processes. The high lipid content of the seeds provides energy for the development of the embryo and seedling until it passes to independent nutrition. Seeds of many plants (coconut palm, castor bean, sunflower, soybean, rapeseed, etc.) serve as raw materials for industrial production of oil.

Protective and thermal insulation. Accumulating in the subcutaneous adipose tissue and around certain organs (kidneys, intestines), the fat layer protects the body from mechanical damage. In addition, due to its low thermal conductivity, the layer of subcutaneous fat helps to retain heat, which allows, for example, many animals to live in cold climates. In whales, in addition, it plays another role - it contributes to buoyancy.

Lubricating and water repellent. Waxes cover the skin, wool, feathers, make them more elastic and protect them from moisture. Leaves and fruits of plants are covered with a wax coating; Wax is used by bees in building honeycombs.

Regulatory. Many hormones are derived from cholesterol, such as sex hormones (testosterone in men and progesterone in women) and corticosteroids (aldosterone).

metabolic. Derivatives of cholesterol, vitamin D play a key role in the exchange of calcium and phosphorus. Bile acids are involved in the processes of digestion (emulsification of fats) and absorption of higher carboxylic acids.

Lipids are the source of metabolic water. When fat is oxidized, approximately 105 g of water is formed. This water is very important for some desert dwellers, in particular for camels that can go without water for 10-12 days: the fat stored in the hump is used for this purpose. Bears, marmots and other animals in hibernation receive the water necessary for life as a result of fat oxidation.

Carbohydrates are organic compounds formed by three chemical elements - carbon, hydrogen and oxygen. Some also contain nitrogen or sulfur. The general formula for carbohydrates is Сm(H2O)n.

They are divided into three main classes: monosaccharides, oligosaccharides (disaccharides) and polysaccharides.

Monosaccharides are the simplest carbohydrates having 3-10 carbon atoms. Most of the carbon atoms in a monosaccharide molecule are associated with alcohol groups, and one is with an aldehyde or keto group.

Glucose (grape sugar) is found in all organisms, including in human blood, since it is an energy reserve, it is part of sucrose, lactose, maltose, starch, cellulose and other carbohydrates. Fructose (fruit sugar) is found in the highest concentrations in fruits, honey, sugar beet root crops. It not only takes an active part in metabolic processes, but also is part of sucrose.

Monosaccharides - crystalline substances, sweet in taste and highly soluble in water.

To oligosaccharides include carbohydrates formed by several monosaccharide residues. They are mostly also crystalline, highly soluble in water and sweet in taste. Depending on the amount of these residues, there are disaccharides (two monosaccharide residues), trisaccharides (three), etc.

Disaccharides include sucrose, lactose and maltose. sucrose (beet or cane sugar) consists of residues of glucose and fructose, it in found in the storage organs of some plants. There is especially a lot of sucrose in the root of the fruits of sugar beet and sugar cane, from where they are obtained industrially. lactose, or milk sugar,formed by residues of glucose and galactose, found in mother's and cow's milk. Maltose (malt sugar) consists of two glucose residues. It is formed during the breakdown of starch in plant seeds and in the human digestive system.

Polysaccharides are biopolymers whose monomers are monosaccharide residues. These include starch, glycogen, cellulose, chitin, etc. The monomer of these polysaccharides is glucose.

Starch is the basicsa vital reserve substance of plants that accumulates in seeds, fruits, tubers, rhizomes and other storage organs. A qualitative reaction to starch is a reaction with iodine, in which starch turns blue-violet.

Glycogen (animal starch) is a reserve polysaccharide of animals and fungi, which in humans accumulates in the largest quantities in the muscles and liver. Glycogen molecules have a higher degree of branching than starch molecules.

Cellulose or fiber - the main reference polysaccharide of plants. Unbranched cellulose molecules form bundles that are part of the cell walls of plants. It is used in the production of textiles, paper, alcohol and other organic substances.

Chitin is a polysaccharide whose monomer is a nitrogen-containing monosaccharidebased on glucose. It is part of the cell walls of fungi and arthropod shells.

Polysaccharides are powdered substances that are unsweetenedtasteless and insoluble in water.

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Functions of carbohydrates

Carbohydrates perform plastic (construction) in the cell, energygetic, storage and support functions. They form the cell walls of plantsand mushrooms. The energy value of the breakdown of 1 g of carbohydrates is 17.2 kJ. Glucose, fructose, sucrose, starch and glycogen are reserve substances. Carbohydrates canalso be part of complex lipids and proteins, forming glycolipids and glycoproteins.

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Lipids

Lipids is a chemically heterogeneous group of hydrophobic substances. These substances do not dissolve in water, but can dissolve in organic solvents.
They form emulsions in water. Lipids are greasy to the touch, many of them leave characteristic non-drying marks on paper. Along with proteins and carbohydrates, they areone of the main components of cells. The content of lipids in different cells is not the same, especially in the seeds and fruits of some plants, in the liver and heart.

By chemical structure, lipids are divided into fats, waxes, steroids, phospholipids, glycolipids, etc.

Fats, or triacylglycerols,are esters of the trihydric alcohol glycerol and higher fatty acids. The fat molecule has dual properties, since the glycerol residue forms a hydrophilic “head”, and fatty acid residues form hydrophobic “tails”.

Most fatty acids contain 14–22 carbonnative atom. Among them there are both saturated andand unsaturated, that is, containing double bonds.

Steroids have molecules with multiple cycles. These include an obligatory component of cell membranes - cholesterol (cholesterol), hormones estradiol and testosterone. ron, vitamin D.

Phospholipids - polar lipids. In addition to glycerol and fatty acid residues, theyhave a phosphoric acid residue. Phospholipids are the basis of cell membranes and provide their barrier properties.

Waxes are esters of higher fatty acids and high molecular weight alcohols. In plants, they form a film on the surface of organs - leaves, fruits. These connectionsprotect the ground organs of plants from excessive moisture loss, prevent the penetration of pathogens, etc. In insects, they cover the body or serve to build honeycombs.

Glycolipids are also components of membranes, but their content there is low.The non-lipid portion of glycolipids includes a carbohydrate residue.

Functions of lipids.

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Reserve - fats are deposited in the stock in the tissues of vertebrates.

Energy - half of the energy consumed by the cells of vertebrates at rest is formed as a result of fat oxidation. Fats are also used as a source of water. The energy effect from the breakdown of 1 g of fat is 39 kJ, which is twice the energy effect from the breakdown of 1 g of glucose or protein.
Protective - the subcutaneous fat layer protects the body from mechanical damage.
Structural Phospholipids are part of cell membranes.
Thermal insulation - subcutaneous fat helps to keep warm.
electrical insulating - myelin, secreted by Schwann cells (form the sheaths of nerve fibers), isolates some neurons, which many times accelerates the transmission of nerve impulses.
Nutritious - Some lipid-like substances contribute to building muscle mass, maintaining body tone.
Lubricating Waxes cover the skin, wool, feathers and protect them from water. The leaves of many plants are covered with a wax coating; wax is used in the construction of honeycombs.
Hormonal - adrenal hormone - cortisone and sex hormones are lipid in nature.

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THEMATIC ASSIGNMENTS

Part A

A1. A polysaccharide monomer can be:
1) amino acid
2) glucose
3) nucleotide
4) cellulose

A2. In animal cells, the storage carbohydrate is:
1) cellulose
2) starch
3) chitin
4) glycogen

A3. Most energy is released during splitting:
1) 10 g protein
2) 10 g glucose
3) 10 g fat
4) 10 g amino acid

A4. What function do lipids not perform?
1) energy
2) catalytic
3) insulating
4) storage

A5. Lipids can be dissolved in:
1) water
2) salt solution
3) hydrochloric acid
4) acetone

Part B

IN 1. Select the features of the structure of carbohydrates
1) consist of amino acid residues
2) consist of glucose residues
3) consist of hydrogen, carbon and oxygen atoms
4) some molecules have a branched structure
5) consist of fatty acid residues and glycerol
6) consist of nucleotides

IN 2. Select the functions that carbohydrates perform in the body
1) catalytic
2) transport
3) signal
4) building
5) protective
6) energy

VZ. Select the functions that lipids perform in the cell
1) structural
2) energy
3) storage
4) enzymatic
5) signal
6) transport

AT 4. Match the group of chemical compounds with their role in the cell:

Part C

C1. Why does not glucose accumulate in the body, but starch and glycogen accumulate?

Test 2

Part 1 contains 10 tasks (A1-10). Each question has 4 possible answers, one of which is correct.

Part 1

A 1. Monosaccharide, the molecule of which contains five carbon atoms

1. glucose

2. fructose

3. galactose

4. deoxyribose

A 2. Chemical bond connecting the residues of glycerol and higher fatty acids in a fat molecule

1. covalent polar

2. covalent non-polar

4. hydrogen

A 3. The monomer of starch and cellulose is

1. glucose

2. glycerin

3. nucleotide

4. amino acid

A 4. Which of the substances will dissolve lipids

3. physiological saline

4. hydrochloric acid

A 5. Winter hardiness of plants increases with accumulation in cells:

1. starch

3. sugars

4. mineral salts

A 6. What foods contain the most carbohydrates needed by a person?

1. in cheese and cottage cheese

2. bread and potatoes

3. meat and fish

4. vegetable oil

A 7. The end products of glycogen in the cell are

1. ATP and water

2. oxygen and carbon dioxide

3. water and carbon dioxide

4. ATP and oxygen

A 8. The reserve carbohydrate in the animal cell is

1. starch

2. glycogen

3. cellulose

A 9. Juice that does not contain enzymes, but facilitates the absorption of fats in the small intestine

1. gastric juice

2. pancreatic juice

3. intestinal juice

A 10. In humans, food carbohydrates begin to be digested in

1. duodenum

2. oral cavity

3. stomach

4. large intestine

Part 2 contains 8 tasks (B1-B8): 3 - with the choice of three correct answers out of six, 3 - for correspondence, 2 - for establishing the sequence of biological processes, phenomena, objects.

Part 2

B 1. Lipids found only in animals

1. cholesterol

2. lipoproteins

3. triglycerides

4. phospholipids

5. bile acids

6. testosterone

B 2. Monosaccharides are

2. sucrose

3. lactose

4. glucose

5. maltose

6. galactose

AT 3. Complex organic compounds, the molecule of which includes a carbohydrate component

1. ribonucleotides

2. phospholipids

3. deoxyribonucleotides

4. amino acids

5. adenosine triphosphate

6. cholesterol

B 4. Forms of carbohydrates in plant and animal cells

Cell Carbohydrate

A) plant cells 1. glycogen

B) animal cells 2. starch

3. cellulose

4. heparin

B 5. Establish a correspondence between the characteristic and organic matter

Characteristic Organic matter

1. Composed of carbon, hydrogen and oxygen A. Carbohydrates

2. Low thermal conductivity B. Fats

3. Form biopolymers - polysaccharides

4. Provide interaction of cells of the same type

5. They are all non-polar

6. Practically insoluble in water

B 6. Establish a correspondence between a carbohydrate and the group of carbohydrates to which they belong

Carbohydrate name Carbohydrate group

1. Glucose A. monosaccharides

2. Sucrose B. Disaccharides

3. Galactose B. Polysaccharides

4. Starch

5. Maltose

6. Lactose

B 7. Arrange monosaccharides in ascending order of the number of carbon atoms in their molecule

1. dihydroxyacetone (ketose)

2. glucose

3. elythrose threose

5. glucosamine

6. Frame-O

B 8. Arrange fats in ascending order of carbon atoms in their molecule

1. tripalmitin

2. tristearin

3. trilaurin

4. tricaprylin

5. trimyristin

Part 3 contains 6 tasks. For task C1, give a short free answer, and for tasks C2-C6 - a full detailed answer.

Part 3

С 1. What role do phospholipids and glycolipids play for living organisms?

C 2. Indicate the numbers of proposals in which errors were made. Explain them.

1. Carbohydrates are compounds of carbon and hydrogen.

2. There are three classes of carbohydrates - monosaccharides, disaccharides and polysaccharides.

3. The most common monosaccharides are sucrose and lactose.

4. They are water soluble and have a sweet taste.

5. When 1 g of glucose is broken down, 35.2 kJ of energy is released

C 3. What are the functions of carbohydrates in plant cells?

C 4. Explain why the storage function is performed by polysaccharides, and not monosaccharides?

Answers:

Part 1

A1-4 A6-2

A2-1 A7-3

A3-1 A8-2

A4-2 A9-4

A5-3 A10-2

Part 2

B1-1 3 4

B2-1 4 6

B3-1 3 5

B4 -A 2 3, B 1 4

B5-A 1 3 4, B 2 5 6

V6-A1 3, B 2 5 6, V 4

B7-1 3 4 2 5 6

B8-4 3 5 1 2

Part 3

C 1. Phospholipids and glycolipids are components of cell membranes.

C 2. 1. carbon and water.

3. disaccharides.

5. 17.6 kJ

C 3. 1. Monosaccharides and disaccharides perform an energy function.

2. Starch is a reserve nutrient.

3. Cellulose is part of the cell walls.

C 4. 1. Since polysaccharides are insoluble in water, they do not have an osmotic and chemical effect on the cell.

2. In the solid and dehydrated state, they have a smaller volume and a larger useful mass.

3. Less accessible to pathogenic bacteria and fungi, since these organisms absorb food rather than swallow it.

4. If necessary, they are easily converted into monosaccharides.

A group of organic substances, including fats and fat-like substances (lipoids), is called lipids. Fats are found in all living cells, act as a natural barrier, limiting the permeability of cells, and are part of hormones.

Structure

Lipids by chemical nature are one of the three types of vital organic substances. They practically do not dissolve in water; are hydrophobic compounds, but form an emulsion with H 2 O. Lipids decompose in organic solvents - benzene, acetone, alcohols, etc. By physical properties, fats are colorless, tasteless and odorless.

By structure, lipids are compounds of fatty acids and alcohols. When additional groups (phosphorus, sulfur, nitrogen) are attached, complex fats are formed. A fat molecule necessarily includes carbon, oxygen and hydrogen atoms.

Fatty acids are aliphatic, i.e. not containing cyclic carbon bonds, carboxylic (-COOH group) acids. They differ in the number of -CH2- groups.
Producing acids:

• unsaturated - include one or more double bonds (-CH=CH-);
• rich - do not contain double bonds between carbon atoms

Rice. 1. The structure of fatty acids.

In cells, they are stored in the form of inclusions - drops, granules, in a multicellular organism - in the form of adipose tissue, consisting of adipocytes - cells capable of accumulating fats.

Classification

Lipids are complex compounds that occur in various modifications and perform various functions. Therefore, the classification of lipids is extensive and is not limited to one feature. The most complete classification by structure is given in the table.

The lipids described above are saponifiable fats - when they are hydrolyzed, soap is formed. Separately, in the group of unsaponifiable fats, i.e. do not interact with water, release steroids.
They are divided into subgroups depending on the structure:

• sterols - steroid alcohols that are part of animal and plant tissues (cholesterol, ergosterol);
• bile acids - derivatives of cholic acid, containing one group -COOH, contribute to the dissolution of cholesterol and the digestion of lipids (cholic, deoxycholic, lithocholic acids);
• steroid hormones - contribute to the growth and development of the body (cortisol, testosterone, calcitriol).

Rice. 2. Scheme for the classification of lipids.

Lipoproteins are isolated separately. These are complex complexes of fats and proteins (apolipoproteins). Lipoproteins are classified as complex proteins, not fats. They include a variety of complex fats - cholesterol, phospholipids, neutral fats, fatty acids.
There are two groups:

• soluble - are part of the blood plasma, milk, yolk;
• insoluble - are part of the plasmalemma, the sheath of nerve fibers, chloroplasts.

Rice. 3. Lipoproteins.

Plasma lipoproteins have been studied the most. They vary in density. The more fat, the lower the density.

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Lipids are classified according to their physical structure into solid fats and oils. By being in the body, reserve (non-permanent, dependent on nutrition) and structural (genetically determined) fats are isolated. By origin, fats can be vegetable and animal.

Meaning

Lipids must be ingested with food and participate in metabolism. Depending on the type of fats perform in the body various functions:

• triglycerides keep the body warm;
• subcutaneous fat protects internal organs;
• phospholipids are part of the membranes of any cell;
• adipose tissue is a reserve of energy - the breakdown of 1 g of fat gives 39 kJ of energy;
• glycolipids and a number of other fats perform a receptor function - they bind cells, receiving and conducting signals received from the external environment;
• phospholipids are involved in blood clotting;
• waxes cover the leaves of plants, at the same time protecting them from drying out and getting wet.

An excess or deficiency of fats in the body leads to a change in metabolism and a violation of the functions of the body as a whole.

What have we learned?

Fats have a complex structure, are classified according to different criteria and perform a variety of functions in the body. Lipids are made up of fatty acids and alcohols. When additional groups are attached, complex fats are formed. Proteins and fats can form complex complexes - lipoproteins. Fats are part of the plasmalemma, blood, tissues of plants and animals, perform heat-insulating and energy functions.

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The structure of lipids, fatty acids

Lipids - a fairly large group of organic compounds present in all living cells that do not dissolve in water, but dissolve well in non-polar organic solvents (gasoline, ether, chloroform, benzene, etc.).

Remark 1

Lipids have a wide variety of chemical structures, but true lipids are esters of fatty acids and any alcohol.

At fatty acids the molecules are small and have a long chain, most often consisting of 19 or 18 carbon atoms. The molecule also contains hydrogen atoms and carboxyl group(-COOH). Their hydrocarbon "tails" are hydrophobic, and the carboxyl group is hydrophilic, therefore esters are easily formed.

Sometimes fatty acids have one or more double bonds (C-C). In this case, fatty acids, as well as the lipids that contain them, are called unsaturated .

Fatty acids and lipids that do not have double bonds are called rich . They are formed by the addition of an additional pair of hydrogen atoms at the site of the double bond of an unsaturated acid.

Unsaturated fatty acids melt at lower temperatures than saturated ones.

Example 1

Oleic acid (Tmelt = 13.4°C) is liquid at room temperature, while palmitic and stearic acids (Tmelt = 63.1 and 69.9°C respectively) remain solid under these conditions.

Definition 1

Most lipids are esters of the trihydric alcohol glycerol and three fatty acid residues. These connections are called triglycerides, or triacylglycerols.

Fats and oils

Lipids are divided into fats and oils . It depends on the state in which they remain at room temperature: solid (fats), or liquid (oils).

The melting point of lipids is the lower, the greater the proportion of unsaturated fatty acids in them.

Oils tend to have more unsaturated fatty acids than fats.

Example 2

In the body of animals living in cold climatic zones (fish of the Arctic seas) there are usually more unsaturated triacylglycerols than in the inhabitants of southern latitudes. Therefore, their body remains flexible even at low ambient temperatures.

Functions of lipids

Important groups of lipids include

• steroids (cholesterol, bile acids, vitamin D, sex hormones, etc.),
• terpenes (carotenoids, vitamin K, plant growth substances - gibberellins),
• waxes,
• phospholipids,
• glycolipids,
• lipoproteins.

Remark 2

Lipids are an important source of energy.

As a result of oxidation, lipids provide twice as much energy as proteins and carbohydrates, that is, they are an economical form of storage of reserve nutrients. This is due to the fact that lipids contain more hydrogen and very little oxygen compared to proteins and carbohydrates.

Example 3

Hibernating animals accumulate fats, and dormant plants accumulate oils. Spend them later in the process of life. Due to the high content of lipids, plant seeds provide energy for the development of the embryo and sprout until it passes to independent nutrition. Seeds of many plants (sunflower, soybean, flax, corn, mustard, coconut palm, castor oil, etc.) are raw materials for industrial production of oils.

Due to their insolubility in water, lipids are an important structural component cell membranes, which are mainly composed of phospholipids. In addition, they contain glycolipids and lipoproteins.

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