A living cell of any organism consists of 25–30% organic components.
Organic components include both polymers and relatively small molecules - pigments, hormones, ATP, etc.
The cells of living organisms differ from each other in structure, functions and in their biochemical composition. However, each group of organic substances has a similar definition in a biology course and performs the same functions in any type of cell. The main constituents are fats, proteins, carbohydrates and nucleic acids.
In contact with
Classmates
Lipids
Lipids are called fats and fat-like substances. This biochemical group is distinguished by good solubility in organic substances, but it is insoluble in water.
Fats can be solid or liquid. The first is more typical for animal fats, the second - for vegetable fats.
The functions of fats are as follows:
Carbohydrates
Carbohydrates are organic monomeric and polymeric substances that contain carbon, hydrogen and oxygen in their composition. When they are broken down, the cell receives a significant amount of energy.
According to the chemical composition, the following classes of carbohydrates are distinguished:
Compared to animal cells, vegetable contain in their composition a greater amount of carbohydrates. This is due to the ability of plant cells to reproduce carbohydrates during photosynthesis.
The main functions of carbohydrates in a living cell are energy and structural.
energy function carbohydrates is reduced to the accumulation of energy reserves and their release as needed. Plant cells accumulate starch during the growing season, which is deposited in tubers and bulbs. In animal organisms, this role is played by the polysaccharide glycogen, which is synthesized and accumulated in the liver.
structural function carbohydrates are made in plant cells. Almost the entire cell wall of plants is made up of the polysaccharide cellulose.
Squirrels
Proteins are organic polymeric substances, which occupy a leading place both in quantity in a living cell and in their significance in biology. The entire dry mass of an animal cell consists of approximately half of the protein. This class of organic compounds is remarkably diverse. Only in the human body there are about 5 million different proteins. They not only differ from each other, but also have differences with the proteins of other organisms. And all this colossal variety of protein molecules is built from only 20 varieties of amino acids.
If a protein is exposed to thermal or chemical factors, hydrogen and bisulfide bonds are destroyed in the molecules. This leads to protein denaturation and changes in the structure and function of the cell membrane.
All proteins can be conditionally divided into two classes: globular (these include enzymes, hormones and antibodies), and fibrillar - collagen, elastin, keratin.
Functions of a protein in a living cell:
Nucleic acids
Nucleic acids are essential for the structure and proper functioning of cells. The chemical structure of these substances is such that it allows you to save and inherit information about the protein structure of cells. This information is transmitted to daughter cells and at each stage of their development a certain type of protein is formed.
Since the vast majority of the structural and functional features of a cell are due to their protein component, the stability that distinguishes nucleic acids is very important. In turn, the development and condition of the organism as a whole depends on the stability of the structure and functions of individual cells.
There are two types of nucleic acids - ribonucleic (RNA) and deoxyribonucleic (DNA).
DNA is polymer molecule, which consists of a pair of helices of nucleotides. Each monomer of the DNA molecule is represented as a nucleotide. Nucleotides are composed of nitrogenous bases (adenine, cytosine, thymine, guanine), a carbohydrate (deoxyribose) and a phosphoric acid residue.
All nitrogenous bases are connected to each other in a strictly defined way. Adenine is always located against thymine, and guanine is always located against cytosine. This selective connection is called complementarity and plays a very important role in the formation of protein structure.
All adjacent nucleotides are linked to each other by a phosphoric acid residue and deoxyribose.
Ribonucleic acid has a strong resemblance to deoxyribonucleic acid. The difference lies in the fact that instead of thymine, the nitrogenous base uracil is present in the structure of the molecule. Instead of deoxyribose, this compound contains the carbohydrate ribose.
All nucleotides in the RNA chain are connected through a phosphorus residue and ribose.
By its structure RNA can be single or double stranded. In a number of viruses, double-stranded RNAs perform the functions of chromosomes - they are carriers of genetic information. With the help of single-stranded RNA, information about the composition of the protein molecule is transferred.
Organic compounds make up an average of 20-30% of the cell mass of a living organism. These include biological polymers - proteins, nucleic acids and carbohydrates, as well as fats and a number of small molecules - hormones, pigments, ATP and many others.
Different types of cells contain different amounts of organic compounds. In plant cells, complex carbohydrates - polysaccharides predominate, in animals - more proteins and fats. However, each of the groups of organic substances in any type of cell performs similar functions.
Lipids - so called fats and fat-like substances (lipoids). The substances included here are characterized by solubility in organic solvents and insolubility (relative) in water.
Distinguish vegetable fats, which have a liquid consistency at room temperature, and animals - solid.
Lipid functions:
Structural - phospholipids are part of cell membranes;
Storage - fats accumulate in the cells of vertebrates;
Energy - a third of the energy consumed by the cells of vertebrates at rest is formed as a result of the oxidation of fats, which are also used as a source of water;
Protective - the subcutaneous fat layer protects the body from mechanical damage;
Thermal insulation - subcutaneous fat helps to keep warm;
Electrical insulating - myelin, secreted by Schwann cells, isolates some neurons, which many times accelerates the transmission of nerve impulses;
Nutrient - bile acids and vitamin D are formed from steroids;
Lubricating - waxes cover the skin, wool, feathers of animals and protect them from water; leaves of many plants are covered with a wax coating; wax is used by bees in building honeycombs;
Hormonal - adrenal hormone - cortisone and sex hormones are lipid in nature, their molecules do not contain fatty acids.
When splitting 1 g of fat, 38.9 kJ of energy is released.
Carbohydrates
Carbohydrates are composed of carbon, hydrogen and oxygen. There are the following carbohydrates. When splitting 1 g of a substance, 17.6 kJ of energy is released.
Monosaccharides, or simple carbohydrates, which, depending on the content of carbon atoms, are called triose, pentose, hexose, etc. Pentoses - ribose and deoxyribose - are part of DNA and RNA. Hexose - glucose - serves as the main source of energy in the cell.
Polysaccharides- polymers, the monomers of which are hexose monosaccharides. The best known of the disaccharides (two monomers) are sucrose and lactose. The most important polysaccharides are starch and glycogen, which serve as reserve substances for plant and animal cells, as well as cellulose, the most important structural component of plant cells.
Plants have a greater variety of carbohydrates than animals, as they are able to synthesize them in the light during photosynthesis. The most important functions of carbohydrates in the cell: energy, structural and storage.
The energy role is that carbohydrates serve as a source of energy in plant and animal cells; structural - the cell wall in plants consists almost entirely of cellulose polysaccharide; storage - starch serves as a reserve product of plants. It accumulates in the process of photosynthesis during the growing season and in a number of plants is deposited in tubers, bulbs, etc. In animal cells, this role is played by glycogen, which is deposited mainly in the liver.
Squirrels
Among the organic substances of the cell, proteins occupy the first place, both in quantity and in value. In animals, they account for about 50% of the dry mass of the cell. In the human body, there are about 5 million types of protein molecules that differ not only from each other, but also from the proteins of other organisms. Despite such a variety and complexity of structure, proteins are built from only 20 different amino acids. Part of the proteins that make up the cells of organs and tissues, as well as amino acids that enter the body, but are not used in protein synthesis, undergo decay with the release of 17.6 kJ of energy per 1 g of substance.
Proteins perform many different functions in the body: building (they are part of various structural formations); protective (special proteins - antibodies - are able to bind and neutralize microorganisms and foreign proteins), etc. In addition, proteins are involved in blood clotting, preventing severe bleeding, perform regulatory, signaling, motor, energy, transport functions (transfer of certain substances in the body) .
The catalytic function of proteins is of exceptional importance. The term "catalysis" means "unleashing", "liberation". Substances classified as catalysts accelerate chemical transformations, and the composition of the catalysts themselves after the reaction remains the same as it was before the reaction.
Enzymes
All enzymes that act as catalysts are substances of a protein nature; they accelerate the chemical reactions that take place in the cell by tens and hundreds of thousands of times. The catalytic activity of an enzyme is determined not by its entire molecule, but only by a small part of it - the active center, the action of which is very specific. There can be several active centers in one enzyme molecule.
Some enzyme molecules can consist only of protein (for example, pepsin) - one-component, or simple; others contain two components: a protein (apoenzyme) and a small organic molecule - a coenzyme. It has been established that vitamins function as coenzymes in the cell. If we take into account that not a single reaction in a cell can be carried out without the participation of enzymes, it becomes obvious that vitamins are of great importance for the normal functioning of the cell and the whole organism. The lack of vitamins reduces the activity of those enzymes in which they are included.
The activity of enzymes is directly dependent on the action of a number of factors: temperature, acidity (pH of the environment), as well as the concentration of substrate molecules (the substance they act on), the enzymes themselves and coenzymes (vitamins and other substances that make up coenzymes) .
The action of various biologically active substances, such as hormones, drugs, plant growth stimulants, toxic substances, etc., can stimulate or inhibit this or that enzymatic process.
vitamins
vitamins - biologically active low molecular weight organic substances - are involved in metabolism and energy conversion in most cases as components of enzymes.
The daily human need for vitamins is milligrams, and even micrograms. More than 20 different vitamins are known.
The source of vitamins for humans is food, mainly of plant origin, in some cases - and animal (vitamin D, A). Some vitamins are synthesized in the human body.
A lack of vitamins causes a disease - hypovitaminosis, their complete absence - beriberi, and an excess - hypervitaminosis.
Hormones
Hormones - substances produced by the endocrine glands and some nerve cells - neurohormones. Hormones are able to be included in biochemical reactions, regulating metabolic processes (metabolism and energy).
The characteristic features of hormones are: 1) high biological activity; 2) high specificity (hormonal signals in the "target cells"); 3) remoteness of action (transfer of hormones by blood to a distance to target cells); 4) a relatively short time of existence in the body (several minutes or hours).
Nucleic acids
There are 2 types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
ATP - adenosine triphosphoric acid, a nucleotide consisting of the nitrogenous base of adenine, a ribose carbohydrate and three molecules of phosphoric acid.
The structure is unstable, under the influence of enzymes it passes into ADP - adenosine diphosphoric acid (one molecule of phosphoric acid is split off) with the release of 40 kJ of energy. ATP is the single source of energy for all cellular reactions.
Features of the chemical structure of nucleic acids provide the possibility of storing, transferring and inheriting to daughter cells information about the structure of protein molecules that are synthesized in each tissue at a certain stage of individual development.
Nucleic acids ensure the stable preservation of hereditary information and control the formation of their corresponding enzyme proteins, and enzyme proteins determine the main features of cell metabolism.
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Slides captions:
included in the cell. Akhatova O.V.
Organic substances are compounds containing carbon. Single or double bonds arise between carbon atoms, on the basis of which carbon chains are formed: linear, branched, cyclic. Most organic substances - polymers, consist of repeating particles - monomers. Regular biopolymers are called substances consisting of the same monomers; irregular - consisting of different monomers.
Proteins are irregular biopolymers; monomers - 20 essential amino acids.
The amino group has the properties of a base The radical group is different for everyone The carboxyl group has acidic properties
Between the connected amino acids, a peptide bond arises, on the basis of which a compound is formed - a polypeptide.
Primary - linear, in the form of a polypeptide chain. Secondary - due to hydrogen bonds: spiral - a, in the form of an accordion - b. Tertiary - globular, due to hydrophobic interactions. Quaternary - the combination of several molecules with a tertiary structure.
Proteins Simple Complex
GLOBULAR PROTEINS: antibodies, hormones, enzymes FIBRILLAR: collagen, skin keratin, elastin
Protein functions. Structural - are part of various cell organelles. Transport - the attachment of chemical elements to proteins and their transfer to certain cells. Motor - contractile proteins are involved in all movements of cells and the body. Catalytic - accelerate or slow down biochemical reactions in cells, in organisms.
Protein functions. Energy - when splitting 1 g of protein, 17.6 kJ is released. Hormonal, or receptor - are part of many hormones. They take part in the regulation of life processes. Protective - antibodies (the most important molecules of the immune system) are proteins.
Milk contains casein.
Carbohydrates are cyclic molecules made up of carbon, oxygen, and hydrogen and polymers made up of the same cycles.
Monosaccharides Consist of one cycle (glucose) Disaccharides Consists of two cycles (sucrose) Polysaccharides Consists of many cycles (starch) Carbohydrates
Maltose. Glucose.
Lactose. Sucrose.
Cellulose. Chitin.
Functions of carbohydrates. Energy - can be split into carbon dioxide and soda with the release of energy. Structural - the walls of plant cells are composed of carbohydrates (cellulose).
Lipids are compounds of two or three fatty acid molecules and a complex alcohol molecule.
Functions of lipids. Energy - can decay with the release of a large amount of energy. Serve for long-term storage of energy. Construction - all cell membranes are composed of lipids. Protective - lipid deposits in the form of a fatty layer carry out thermal insulation of the body. Hormonal - some lipids are part of the hormones of the gonads and adrenal glands.
Which statements are true? 1. Proteins are biopolymers. 2. Protein monomers are amino acids. 3. Wax, vitamin D, vegetable and animal fats are lipids. 4. Proteins are the main source of energy. 5. Carbohydrates are carriers of hereditary information.
Which statements are true? 6. Glucose, sucrose - varieties of carbohydrates. 7. Fats dissolve well in water. 8. Carbohydrates perform only a supporting function. 9. Fats serve as a reserve source of energy. 10. Proteins have only a primary structure.
Homework: P.22 to p. 111.
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There are 4 classes of organic substances that make up cells: proteins, fats, carbohydrates and nucleic acids.
Carbohydrates
Carbohydrates - organic substances, which include carbon, oxygen and hydrogen. Formed during photosynthesis from water and carbon dioxide. Distinguish - monosaccharides (consist of one molecule) (glucose, ribose, etc.), disaccharides - a compound of two molecules (sucrose, maltose) and polysaccharides - they include many sugar molecules (starch, glycogen, fiber, pectin, inulin , chitin).
Functions of carbohydrates
1. They are part of many organic substances (ribose - in the composition of RNA, ATP, FAD, NAD, NADP, deoxyribose - in the composition of DNA)
2. Glucose - is a source of energy (oxidized during respiration)
3. Many carbohydrates are reserve substances - starch in plants, glycogen in fungi and animals
4. Included in many components of cells and tissues (glycocalyx, heparin, clycoproteins, pectins, polysaccharides, hemicellulose, chitin, murein, teichoic acids)
5. Protective - as part of the glycocalyx, it participates in the process of cellular recognition, are part of immunoglobulins, are part of gum (released when the trunks are damaged) and are part of the cell wall of many organisms
Squirrels
Squirrels- These are organic polymer substances, the monomers of which are amino acids (hemoglobin, albumin, collagen, elastin, and many others).
Proteins have 4 structures
Primary - a linear sequence of amino acids connected to a polypeptide chain
Secondary - a spiral consisting of two chains connected by hydrogen bonds
Tertiary - globule or fibrillar structure (stacked layers or supertwisted helix). Ionic, hydrogen, covalent (disulfide bridges), hydrophobic interactions between constituents
Quaternary - several globules or microfibrils connected by forces of intermolecular attraction
There are: actually proteins and enzymes.
Enzymes- biological catalysts, not only accelerate, but also carry out most of the reactions in living organisms.
Functions of proteins
1. Enzymatic - accelerate, and in most cases carry out biochemical reactions in the body
2. Structural - are part of all membranes, are a component of connective tissue (bones, cartilage, tendons, skin, hair, nails), are part of mucous secretions (mucoproteins). Virus capsids are made up of proteins. They are part of the karuzhny skeleton of insects.
3. Motor - microtubules (tubulin), the motor apparatus of flagella, actin and myosin - contractile proteins of muscles are made of proteins.
4. Transport - transport through the membrane and inside the cell, as well as blood proteins (hemoglobin carries oxygen, hemocyanin carries oxygen in the blood of invertebrates, serum albumin carries fatty acids, globulins carry metal ions and hormones)
5. Protective - immunity proteins (interferons), blood proteins (prevent blood loss), antioxidants (quench reactive oxygen species)
6. Receptor - glycocalyx proteins (responsible for cellular compatibility), photosensitive enzymes of the retina, phytochrome in plants (reacts to changes in the length of daylight hours)
7. Storage - protein-ferritin stores iron in the liver, spleen, myoglobin stores oxygen in the muscles of vertebrates
8. Nutrient - proteins - sources of amino acids
9. Regulatory - many hormones are proteins (insulin, growth hormone, prolactin, glucagon)
10. Antibiotic - many antibiotics (antimicrobials) are proteins (gramicidin S, actinomycin)
11. Toxic - many toxins (substances dangerous to living organisms) are proteins - botulinum toxin, tetanus, cholera, fungal and bee toxins
Nucleic acids: DNA and RNA
In 1953, British scientists J. Watson and F. Crick proposed a model of the spatial structure of DNA. They showed that DNA consists of two polynucleotide chains, spirally twisted one around the other. The double helix is stabilized by hydrogen bonds between the nitrogenous bases of different chains so that the adenine of one chain is always opposed by the thymine of the other, and guanine by cytosine. The repeated repetition of these bonds makes the DNA double helix more stable. Under certain conditions (the action of acids, alkalis, heating, etc.), DNA denaturation occurs, i.e., the breaking of hydrogen bonds between complementary nitrogenous bases. Denatured DNA can restore the double-stranded structure due to the establishment of hydrogen bonds between complementary nucleotides - this process is called renaturation.
DNA structure:
DNA is made up of 4 types of nitrogenous bases: A (adenine), T (thymine), G (guanine) and C (cytosine).
Nucleotides are connected according to the principle of complementarity: A=T, GΞC
DNA functions:
1. Storage of genetic information
2. DNA replication
3. RNA synthesis
RNA structure:
RNA is:
1. Ribosomal (part of ribosomes)
2. Transport (brings amino acids to ribosomes during protein synthesis)
3. Informational (transmits information about the primary structure of the protein to ribosomes)
Lipids
Lipids are fat-like organic substances that are insoluble in water, but soluble in non-polar organic solvents (benzene, gasoline, etc.).
Composed of glycerol and fatty acids, the glycerol heads are hydrophilic and the hydrocarbon tails are hydrophobic. Thus, a lipid layer is formed in the membrane, through which water and other substances diffuse.
The structure of lipids:
Lipid functions:
1. Energy - when lipids are oxidized, a lot of energy is released
2. Reserve - fats are a reserve substance and during the oxidation of fats water is released, which is very important, for example, for desert residents
3. Structural - membranes of all living organisms are composed of phospholipids, glycolipids are involved in intercellular contacts in animal tissues, sphingolipids provide electrical insulation of the axon, creating conditions for the rapid passage of an impulse, bees build honeycombs from wax
4. Protective - thermal insulation and cushioning, waxes are water-repellent substances in plants, glycolipids are involved in the recognition of toxins
5. Regulatory - some hormones - lipids (testosterone, progesterone, cortisone), there are fat-soluble vitamins (A, D, E, K), gibberellins - plant growth regulators
Diversity of lipids
Phospholipids- contain a residue of phosphoric acid, are part of cell membranes.
Glycolipids- compounds of lipids with carbohydrates. They are an integral part of brain tissue and nerve fibers.
Lipoproteins- complex compounds of various proteins with fats.
Steroids- important components of sex hormones, vitamin D.
Wax- perform a protective function: in mammals - they lubricate the skin and hair, in birds - they give water-repellent properties to feathers, in plants - they prevent excessive evaporation of water.
ATP
Adenosine triphosphoric acid (ATP)- a nucleotide, which includes the nitrogenous base adenine, the carbohydrate ribose and three residues of phosphoric acid. The ATP molecule is a universal chemical energy accumulator in cells. Phosphoric acid residues are linked by macroergic bonds. When one residue of phosphoric acid is cleaved from ATP, ADP is formed - adenosine diphosphoric acid and 40 kJ of energy is released.
Squirrels (proteins, polypeptides) are the most numerous, most diverse and of paramount importance biopolymers. The composition of protein molecules includes atoms of carbon, oxygen, hydrogen, nitrogen and sometimes sulfur, phosphorus and iron.
Protein monomers are amino acids, which (having in their composition carboxyl and amino groups) have the properties of an acid and a base (amphoteric).
Due to this, amino acids can combine with each other (their number in one molecule can reach several hundred). In this regard, protein molecules are large and are called macromolecules.
Structure of a protein molecule
Under the structure of a protein molecule understand its amino acid composition, the sequence of monomers and the degree of twisting of the protein molecule.
In protein molecules, there are only 20 types of different amino acids, and a huge variety of proteins is created due to their various combinations.
- The sequence of amino acids in a polypeptide chain is primary structure of a protein(it is unique to any protein and determines its shape, properties and functions). The primary structure of a protein is unique to any type of protein and determines the shape of its molecule, its properties and functions.
- A long protein molecule folds and first takes the form of a spiral as a result of the formation of hydrogen bonds between the -CO and -NH groups of different amino acid residues of the polypeptide chain (between the carbon of the carboxyl group of one amino acid and the nitrogen of the amino group of another amino acid). This spiral is protein secondary structure.
- Tertiary structure of a protein- three-dimensional spatial “packing” of the polypeptide chain in the form globules(ball). The strength of the tertiary structure is provided by a variety of bonds that arise between amino acid radicals (hydrophobic, hydrogen, ionic and disulfide S-S bonds).
- Some proteins (such as human hemoglobin) have quaternary structure. It arises as a result of the combination of several macromolecules with a tertiary structure into a complex complex. The quaternary structure is held together by fragile ionic, hydrogen, and hydrophobic bonds.
The structure of proteins can be disturbed (subjected to denaturation) when heated, treated with certain chemicals, irradiation, etc. With a weak effect, only the quaternary structure breaks down, with a stronger effect, the tertiary, and then the secondary, and the protein remains in the form of a polypeptide chain. As a result of denaturation, the protein loses its ability to perform its function.
Violation of the quaternary, tertiary and secondary structures is reversible. This process is called renaturation.
The destruction of the primary structure is irreversible.
In addition to simple proteins, consisting only of amino acids, there are also complex proteins, which may include carbohydrates ( glycoproteins), fats ( lipoproteins), nucleic acids ( nucleoproteins) and etc.
Functions of proteins
- Catalytic (enzymatic) function. Special proteins - enzymes- capable of accelerating biochemical reactions in the cell by tens and hundreds of millions of times. Each enzyme speeds up one and only one reaction. Enzymes contain vitamins.
- Structural (building) function- one of the main functions of proteins (proteins are part of cell membranes; keratin protein forms hair and nails; collagen and elastin proteins - cartilage and tendons).
- transport function- proteins provide active transport of ions through cell membranes (transport proteins in the outer membrane of cells), transport of oxygen and carbon dioxide (blood hemoglobin and myoglobin in muscles), transport of fatty acids (blood serum proteins contribute to the transport of lipids and fatty acids, various biologically active substances ).
- Signal function. The reception of signals from the external environment and the transmission of information to the cell occurs due to proteins built into the membrane that can change their tertiary structure in response to the action of environmental factors.
- Contractile (motor) function- provided by contractile proteins - actin and myosin (due to contractile proteins, cilia and flagella move in protozoa, chromosomes move during cell division, muscles contract in multicellular organisms, other types of movement in living organisms improve).
- Protective function- Antibodies provide immune defense of the body; fibrinogen and fibrin protect the body from blood loss by forming a blood clot.
- Regulatory function inherent in proteins hormones(not all hormones are proteins!). They maintain constant concentrations of substances in the blood and cells, participate in growth, reproduction and other vital processes (for example, insulin regulates blood sugar).
- energy function- during prolonged starvation, proteins can be used as an additional source of energy after carbohydrates and fats are used up (with the complete breakdown of 1 g of protein to end products, 17.6 kJ of energy is released). Amino acids released during the breakdown of protein molecules are used to build new proteins.
