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The main content of the topic is the concept of metabolism as a set of chemical reactions that ensure growth, vital activity, reproduction and constant contact and exchange with the environment. All chemical reactions of a living cell can be divided into two types: synthesis reactions (biosynthesis), with the help of which plastic exchange is carried out, and splitting reactions - energy exchange.
Energy metabolism consists of three stages. The first one: PREPARATORY stage. At this stage, large molecules of proteins, nucleic acids, fats, carbohydrates are broken down into smaller ones: glucose, glycerol, fatty acids, nucleotides. This releases a small amount of energy, which is dissipated as heat.
The second stage is oxygen-free or ANAEROBIC. This stage can be considered using the example of glucose breakdown. Note that this does not use oxygen and only produces two molecules ATP. It must be taken into account that in the form ATP Only 40% of the energy is stored, the rest is dissipated as heat.
The third stage is oxygen or AEROBIC. The peculiarity of this stage is that oxygen participates in glycolysis reactions and 36 molecules are formed ATP.
Keep in mind that in cases of great need for energy in eukaryotic cells, the process of energy metabolism can proceed only up to the second stage, that is, only anaerobic glycolysis. When studying plastic metabolism, pay attention to in which cell organelles the synthesis of certain organic substances occurs (carbohydrates, fats, proteins, nucleic acids).
PHOTOSYNTHESIS is the process of formation of organic substances from inorganic ones using light energy. The starting materials for photosynthesis are carbon dioxide and water, which contain significantly less energy than glucose. Consequently, during the process of photosynthesis, solar energy is converted into chemical energy. (Energy changes from one form to another.) Please note: the process of photosynthesis has several key points. The chlorophyll molecule contains a Mg atom. Electrons in the outer orbitals of a metal are unstable. When struck by a photon, an electron is ejected from the atom. But he cannot exist in this state for long. It must return to its place, having previously emitted the energy received from the photon, or give it back. In plants, this energy is not lost in chloroplasts. It is partially used for synthesis ATP, but, most importantly, this electron goes to photolysis of water. The resulting hydrogen ions are used for the synthesis of organic substances, and oxygen is released into the atmosphere. These are light phase reactions. The next phase is conventionally called dark. This is a series of enzymatic reactions during which carbon dioxide is bound and carbohydrates are synthesized. This consumes energy ATP and hydrogen atoms. Biosynthetic reactions include protein synthesis reactions. Before studying this part of the topic, review the structure of proteins, the structure and functions of nucleic acids ( DNA And RNA), the principle of complementarity ( A-T,C-G).Protein biosynthesis occurs with the participation of ribosomes. This complex process begins with synthesis on a molecule DNA molecules mRNA, which occurs in the nucleus. Further mRNA transported from the nucleus to the site of protein synthesis. Please note - molecules mRNA are strictly individual and carry information about only one protein. Synthesis process mRNA called TRANSCRIPTION. In the cytoplasm on mRNA one or more ribosomes are strung together. The process of reading information and protein synthesis is called BROADCASTS. Play a special role in broadcasting tRNA(transport RNA), they ensure consistency of information mRNA protein composition. Moreover, every three nucleotides mRNA one amino acid corresponds, the correspondence is achieved by a structural feature tRNA. An amino acid is attached at one end, and at the other there is a triplet of nucleotides that corresponds to that amino acid. During protein biosynthesis, the principle of complementarity is strictly observed. The correspondence of the triplet is fixed on the ribosome mRNA triplet tRNA and fixation of the amino acid, followed by its attachment to the synthesized protein chain. As the protein strand is synthesized, it folds immediately into a secondary and tertiary structure. The ribosome moves along mRNA from triplet to triplet. All biosynthesis reactions occur with the participation of enzymes and with the expenditure of energy.
The protein biosynthesis scheme can be briefly presented as follows: GENE(plot DNA) - I-RNA - RIBOSOMES with T-RNA - PROTEIN.
IN GENERAL CELL METABOLISM PROCESSES(as opposed to ordinary chemical reactions) THEY ARE CHARACTERIZED BY THEIR DIRECTION, CLEAR LOCALIZATION IN THE CELL, DELIMITATION IN THE SPACE OF THE CELL OF SIMULTANEOUSLY OCCURRING PROCESSES OF SYNTHESIS AND DIVISION, INCREDIBLE SPEED, MATRIX SYNTHESIS OF BIOPOLYMERS.
Question No. 2
Man belongs to the class of mammals, the order of primates. Humans' closest evolutionary relatives are chimpanzees, gorillas and orangutans. This causes the human skeleton to be very similar to the skeletons of other mammals, and especially primates.
The human skeleton, like the skeletons of other mammals, consists of the spine, skull, chest, girdles of the limbs and the skeleton of the limbs themselves. However, humans have a better developed brain than other mammals; humans are distinguished by their ability to work and walk upright. These features left their mark on the structure of the human skeleton.
A comparative series of skeletons, indicating the differences and similarities in their structure:
1 – gorilla; 2 – Neanderthal; 3 – modern man
Thus, the volume of the human cranial cavity is larger than that of any animal with the same body size. The dimensions of the facial part of the skull in humans are smaller than the brain, but in animals it is the other way around. This is due to the fact that animals eat raw food, which is difficult to grind, and therefore they have large jaws and teeth, which are also protective organs. The brain volume of animals relative to body size is much smaller than that of humans. The spine in animals does not have significant curves, but in humans it has 4 curves: cervical, thoracic, lumbar and sacral. These curves appeared in connection with upright walking and provide elasticity to the spine when walking, running, and jumping.
The chest of animals is compressed from front to back. In animals, body weight is distributed between all four limbs and the pelvis is not very massive. In humans, the entire body weight rests on the lower limbs, the pelvis is wide and strong.
The skeleton of the fore and hind limbs of animals does not differ very much from each other. In humans, the bones of the lower extremities are thicker and stronger than those of the upper extremities. There are also strong differences in the structure of the human foot and hand. The structure of the fingers allows a person to perform complex types of work.
Humans, like other mammals, have three types of teeth: canines, incisors and molars, but the number and shape of these teeth in humans and representatives of other orders of mammals vary greatly.
The similarity of the human skeleton and apes is one of the proofs that humans have common ancestors with these apes
Question #3
The role of gymnosperms in nature. Gymnosperms form coniferous and mixed forests, occupying vast areas. They enrich the air with oxygen, which is why they are often called the “lungs of the planet.” Forests regulate snow melting, water levels in rivers, absorb noise, weaken the force of winds, and fix sand. The forest is the habitat of many species of animals that feed on shoots, seeds, and cones of coniferous plants.
Coniferous plants continuously release large amounts of phytoncides into the air (from the Greek phyton and Lat. tsedo - I kill) - substances that inhibit the activity of other organisms. This occurs especially intensively in spruce forests. Thus, according to scientists, 1 m3 of coniferous forest air contains no more than 500 cells of pathogenic bacteria, while urban air contains up to 30–40 thousand. Therefore, sanatoriums and hospitals for people with diseases of the respiratory system are located in coniferous forests.
Gymnosperms play a huge role, if only because most of the land covered with vegetation is covered with gymnosperms - the taiga. It is the main supplier of oxygen in the biosphere, food and shelter for animals, building materials, fuel, paper, raw materials
Ticket No. 7 Question No. 1
Metabolism and energy in the cell (Ticket No. 6 Question No. 1)
Characteristics of the breathing process:
Cellularor tissue respiration- a set of biochemical reactions occurring in the cells of living organisms, during which the oxidation of carbohydrates, lipids and amino acids to carbon dioxide and water occurs.
So, cellular respiration occurs in the cell. But where exactly? Which organelle carries out this process?
All stages of cellular respiration occur in mitochondria. As you know, the main product of mitochondria - ATP molecules - is synonymous with the concept of “energy” in biology. Indeed, the main product of this process is energy, ATP molecules.
1. Give definitions of concepts.
Metabolism- a set of chemical reactions that occur in a living organism to maintain life.
Energy exchange
- the process of metabolic breakdown, decomposition into simpler substances or oxidation of a substance, usually occurring with the release of energy in the form of heat and in the form of ATP.
Plastic exchange
– the totality of all biosynthetic processes occurring in living organisms.
2. Fill out the table.
3. Draw a schematic diagram of the ATP molecule. Label its parts. Indicate the location of high-energy bonds. Write the full name of this molecule.
ATP – adenosine triphosphoric acid
4. What class of organic substances does ATP belong to? Why did you come to this conclusion?
Nucleotide, as it consists of adenine, ribose and three phosphoric acid residues.
5. Using the material in § 3.2, fill out the table.
6. What is the biological role of the stepwise nature of energy metabolism?
The gradual release of energy during energy metabolism allows for more efficient use and storage of energy. With a one-time release of such an amount of energy, most of it would simply not have time to combine with ADP and would be released as heat, which means large losses for the body.
7. Explain why oxygen is necessary for most modern organisms. What process produces carbon dioxide in cells?
Oxygen is necessary for breathing. In the presence of oxygen, organic substances during respiration are completely oxidized to carbon dioxide and water.
8. How did the accumulation of oxygen in the Earth’s atmosphere affect the intensity of the life processes of the inhabitants of our planet?
Oxygen has a profound effect on the body as a whole, increasing the overall vital energy of the inhabitants of our planet. New organisms arose and evolved.
9. Fill in the missing words.
Plastic exchange reactions occur with the absorption of energy.
Energy metabolism reactions occur with the release of energy.
The preparatory stage of energy metabolism takes place in the gastrointestinal tract and lysosomes
cells.
Glycolysis occurs in the cytoplasm.
During the preparatory stage, proteins are converted into amino acids by digestive enzymes.
10. Choose the correct answer.
Test 1.
Which abbreviation denotes the carrier of energy in a living cell?
3) ATP;
Test 2.
At the preparatory stage of energy metabolism, proteins break down to:
2) amino acids;
Test 3.
As a result of oxygen-free oxidation in animal cells with a lack of oxygen, the following is formed:
3) lactic acid;
Test 4.
Energy that is released in the reactions of the preparatory stage of energy metabolism:
2) dissipates in the form of heat;
Test 5.
Glycolysis is provided by enzymes:
3) cytoplasm;
Test 6.
The complete oxidation of four glucose molecules produces:
4) 152 ATP molecules.
Test 7.
For the fastest possible recovery from fatigue during exam preparation, it is best to eat:
3) a piece of sugar;
11. Make up a syncwine for the term “metabolism”.
Metabolism
Plastic and energetic.
Synthesizes, destroys, transforms.
A set of chemical reactions in a living organism to maintain life.
Metabolism.
12. Metabolic rate is not constant. Indicate some external and internal reasons that, in your opinion, can change the metabolic rate.
External – ambient temperature, physical activity, body weight.
Internal – the level of hormones in the blood, the state of the nervous system (suppression or excitation).
13. You know that there are aerobic and anaerobic organisms. What are facultative anaerobes?
These are organisms whose energy cycles follow an anaerobic path, but are able to exist with the access of oxygen, in contrast to obligate anaerobes, for which oxygen is destructive.
14. Explain the origin and general meaning of the word (term), based on the meaning of the roots that make it up.
15. Select a term and explain how its modern meaning matches the original meaning of its roots.
The chosen term is glycolysis.
Correspondence: The term matches but is complemented. The modern definition of glycolysis is not just the “breakdown of sweets,” but the process of glucose oxidation, in which two PVK molecules are formed from one molecule, carried out sequentially through several enzymatic reactions and accompanied by the storage of energy in the form of ATP and NADH.
16. Formulate and write down the main ideas of § 3.2.
Any organism is characterized by a metabolism - a set of chemicals. reactions to maintain life. Energy metabolism is the process of decomposition into simpler substances, which occurs with the release of energy in the form of heat and in the form of ATP. Plastic metabolism is the totality of all biosynthetic processes occurring in living organisms.
The ATP molecule is a universal energy supplier in cells.
Energy metabolism occurs in 3 stages: the preparatory stage (glucose and heat are formed), glycolysis (PVC, 2 ATP molecules and heat are formed) and oxygen, or cellular respiration (36 ATP molecules and carbon dioxide are formed).
Metabolism of substances and energy (metabolism) occurs at all levels of the body: cellular, tissue and organismal. It ensures the constancy of the internal environment of the body - homeostasis - in continuously changing conditions of existence. Two processes occur simultaneously in a cell: plastic metabolism (anabolism or assimilation) and energy metabolism (fatabolism or dissimilation).
Plastic exchange is the totality of all synthesis processes when complex substances are formed from simple substances, while energy is expended.
Energy metabolism is the totality of all splitting processes when complex substances are formed into simple ones and energy is released.
Homeostasis is maintained by the balance between plastic and energy metabolism. If this balance is disturbed, then pathologies (diseases) arise in the body or part of it.
Metabolism occurs at normal temperature, pressure and a certain pH environment
11.Energy metabolism in the cell.
Energy metabolism is a set of chemical reactions of the gradual breakdown of organic compounds, accompanied by the release of energy, part of which is spent on the synthesis of ATP. Synthesized ATP becomes a universal source of energy for the life of organisms.
Stages of energy metabolism:
1. Preparatory - on it complex substances are broken down into simple ones, for example polysaccharides into monosaccharides. This stage occurs in the cytoplasm and releases energy, but very little energy is therefore dissipated as heat.
2. Oxygen-free - in lysosomes, at this stage the breakdown of substances into simpler ones continues without the participation of oxygen with the release of two ATP molecules
3. Oxygen - it continues the breakdown of substances with the participation of oxygen to the final products (carbon dioxide and water) with the release of 36 ATP. This process occurs in mitochondria.
Cell nutrition. Chemosynthesis
Cell nutrition occurs as a result of a series of complex chemical reactions, during which substances that enter the cell from the external environment (carbon dioxide, mineral salts, water) enter the body of the cell itself in the form of proteins, sugars, fats, oils, nitrogen and phosphorus. connections.
All living organisms can be divided into 2 groups:
1. Autotrophic type of nutrition - these include organisms that themselves synthesize organic compounds from inorganic ones.
2 types of autotrophs:
Photosynthetics are autotrophs that use the energy of sunlight (plants, cyanobacteria, protozoa)
Chemosynthetics are organisms that use the energy of chemical bonds. This type includes almost all bacteria (nitrogen fixers, sulfur bacteria, iron bacteria)
Chemosynthesis was discovered by Vinogradov.
Chemosynthesis is a method of autotrophic nutrition in which the source of energy for the synthesis of organic substances from CO2 is the oxidation reactions of inorganic compounds. This option for obtaining energy is used only by bacteria or archaea.
2. Heterotrophic type of nutrition - characteristic of organisms that feed on ready-made organic compounds.
Soprophytes are heterotrophs that feed on dead tissues or organisms (crows, vultures, hyenas..)
Plant-eating - heterotrophs that eat plant organisms (herbivores)
Carnivores (predators) are heterotrophs that catch and eat other organisms (insectivores)
Omnivores - eat plant and animal foods
3. Mixotrophic type of nutrition - combines autotrophic and heterotrophic types of nutrition (sundew, green euglena)
Photosynthesis
Photosynthesis is a complex process of formation of inorganic substances using the energy of sunlight. The main organ of photosynthesis is the leaf because it contains the most chloroplasts and its shape is most suitable for receiving sunlight.
Phases of photosynthesis:
1. Light phase - includes 2 main processes: photolysis of water and non-cyclic phosphorylation.
Thylakoids are flattened membrane sacs on which chlorophyll pigments and a special electron carrier called cytochrome are located.
There are 2 photo systems located on the thylakoids:
Photosystem 1 contains chlorophyll a1, which perceives a light quantum with a length of 700 nanometers
Photosystem 2 contains chlorophyll a2, which perceives a light quantum with a length of 680 nanometers
When a quantum of light hits photosystem 1, the electrons of chlorophyll a1 are excited and transferred to a process such as the fatolysis of water, i.e. Water is split into hydrogen and a hydroxo group. Hydrogen is used to reduce the substance. The resulting hydroxo group accumulates and is converted into water and oxygen, which leaves the cell.
When a light quantum hits photosystem 2, the electrons of chlorophyll are excited under the influence of light and a phosphoric acid residue is added to the ADP molecule due to energy, resulting in an ATP molecule.
The light phase occurs on thylakods, where the energy necessary for the formation of organic substances is generated.
Dark phase - occurs in the stroma, independent of sunlight. Here, in the course of complex reactions, carbon dioxide is converted into glucose using the energy generated. These reactions are called the Calvin cycle.
Genetic code
This is a method characteristic of all living organisms of encoding the amino acid sequence of proteins using a sequence of nucleotides
DNA can contain 4 nitrogenous bases:
Adenine, Guanine, Thymine, Cytosine
DNA can code for 64 amino acids
Properties:
1. Degeneracy - increases the reliability of storage and transmission of genetic information during cell division
2. Specificity - 1 triplet always encodes only 1 amino acid
Genetic co is universal for all living organisms from bacteria to humans
15. Transcription and broadcast
Protein synthesis includes 2 stages:
1. Transcription is the transcription of information from a DNA molecule to messenger RNA
This process takes place in the nucleus with the participation of the enzyme RNA polymerase. This enzyme determines the beginning and end of synthesis. The beginning is a specific sequence of nucleotides called a promoter. The end is also a sequence of nucleotides called a terminator.
Transcription begins with determining the section of the DNA molecule from which information will be copied
Then this section unwinds according to the principle of complementarity to one DNA strand and messenger RNA is built. After DNA synthesis is complete, it twists again.
2. Translation is the translation of the messenger RNA tucleotide sequence into an amino acid sequence
Transfer RNA carries messenger RNA to the ribosome. Here, messenger RNA is integrated into the small subunit of the ribosome, but only 2 triplets fit into it, so during synthesis, messenger RNA moves into the large subunit, transfer RNA carries amino acids, if the amino acid is suitable, then it is separated from the transfer RNA and attached to other amino acids according to the peptide principle connections.
Transfer RNA leaves the ribosome, and new transfer RNAs enter the large subunit
If the amino acid does not match the information in the small subunit according to the principle of complementarity, then this transport RNA with the amino acid leaves the ribosome
The beginning of protein synthesis is indicated by adenine, uracil, guanine, and ends with stop cadone
When protein synthesis ends, the primary structure of the protein is separated from the ribosome and the protein takes on the desired structure
Cell life cycle
The cell cycle is the period of cell existence from the moment of its formation by dividing the mother cell until its own division or death.
Interphase is the phase in the life cycle between two cell divisions. It is characterized by active metabolic processes, protein and RNA synthesis, accumulation of nutrients by the cell, growth and increase in volume. In the middle of interphase, DNA duplication (replication) occurs. As a result, each chromosome contains 2 DNA molecules and consists of two sister chromatids, which are linked by a centromere and form one chromosome. The cell prepares for division, all its organelles double. The duration of interphase depends on the type of cell and on average accounts for 4/5 of the total time of the cell life cycle. Cell division. The growth of an organism occurs through the division of its cells. The ability to divide is the most important property of cellular life. When a cell divides, it doubles all its structural components, resulting in two new cells. The most common method of cell division is mitosis - indirect cell division. Mitosis is the process of producing two daughter cells identical to the original mother cell. It ensures cell renewal during the aging process. Mitosis consists of four sequential phases:
1. Prophase - formation of chromosomes with two chromatids, destruction of the nuclear membrane.
2.Metophase—formation of the spindle, shortening of chromosomes, formation of the equaterial cell
3. Anaphase - separation of chromatids, their divergence to the poles along the spindle fibers
4. Telophase - Disappearance of the spindle, formation of nuclear membranes, discoiling of chromosomes.
Mitosis. Amitosis
Mitosis is the process of indirect division of somatic cells of eukaryotes, as a result of which the hereditary material is first doubled and then evenly distributed between daughter cells. It is the main way eukaryotic cells divide. The duration of mitosis in animal cells is 30-60 minutes, and in plant cells - 2-3 hours. It consists of 4 main phases:
1. Prophase - begins with the speralization of DNA chains to chromosomes, the nucleoli and nuclear membrane are destroyed, the chromosomes begin to float freely in the cytoplasm. At the end of prophase, the spindle begins to form
2. Metaphase - chromosomes line up strictly at the equator in the form of a metaphase plate. The spindle threads, which are already fully formed, pass through the centromeres of the chromosomes dividing the chromosome into 2 chromatids
3. Anaphase - Here the spindle filaments separate and stretch to different poles of the chromatid. The fission spindle begins to collapse.
4. Telophase Here, at the poles of the cell, the chromatids are dispersed, covered with a nuclear membrane, and the division of the cytoplasm and the cell itself begins.
As a result of mitosis, 2 identical diploid cells are formed.
Karyokenesis is nuclear division
Cytokenesis is the division of the cytoplasm and the cell itself
Amitosis is the direct division of the nucleus resulting in the formation of a cell with two nuclei, this type is characteristic of muscle cells and connective tissues
This is necessary for the full organization of cell work.
If suddenly such a cell divides, then the new cells will contain an incomplete genetic set, which will lead to their death or make them a pathogen.
Meiosis
This is an indirect division of germ cells resulting in the formation of 4 haploid daughter cells with different genetic materials. This is the main stage in the formation of germ cells.
Biological significance of meiosis:
1. Thanks to meiosis, genetically different gametes are formed
2. The constancy of the diploid set of chromosomes in somatic cells is maintained
3. Thanks to meiosis, 1 cell produces 4 new cells
Meiosis includes 2 divisions:
Reduction - during this division the number of chromosomes decreases
Equational - proceeds the same way as mitosis
Interphase proceeds in the same way as mitosis, i.e. DNA doubles in the nucleus of a dividing cell.
1 meiotic division
Prophase is the most complex and longest phase of meiosis because 2 additional processes appear here.
1- Conjugation is a close approach of homologous chromosomes resulting in the formation of 4 chromatids united by 1 centromere and such a structure will be called a bivalent. Then crossing over occurs between the chromosomes that are united into a bivalent.
2- Crossing over - exchange of chromosome sections. As a result of these processes, 1 gene recombination occurs
Metaphase - here, at the equator of the cell, bivalents form a metaphase plate, through the centromeres of which the filaments of the spindle also pass
Anaphase - unlike mitosis, here whole chromosomes disperse to the poles of the cell. 2 gene recombinations take place here
Telophase - in animals and some plants, chromosomes begin to unwind, become covered with a nuclear membrane at the poles and split into 2 cells (only in animals)
In plants, after anaphase, prophase 2 immediately occurs.
Interphase is characteristic only of animals; unlike the interphase of mitosis, there is no increase in hereditary information
Division 2 of meiosis includes prophase, metaphase, telophase, anaphase, which proceed exactly as in mitosis but with fewer chromosomes.
Asexual reproduction.
This is a type of reproduction that is characterized by:
2. 1 individual participates
3. occurs under favorable conditions
4. all organisms turn out the same
5. retains the properties and characteristics of stably unchanging conditions
Biological significance:
1. necessary for the emergence of organisms with identical anatomical properties
2. in evolutionary terms, asexual reproduction is not profitable, but thanks to this reproduction, the number of individuals within the population increases in a short time
Types of asexual reproduction:
Mitotic division - occurs due to mitosis (amoeba, algae, bacteria...)
Sporulation is carried out through spores, specialized cells of fungi and plants. If a spore has a flagellum, then it is called a zoospore and is characteristic of an aquatic environment (spores, fungi, lichens..)
Humping - on the mother individual, an outgrowth occurs - a bud (contains a daughter nucleus) from which a new individual develops. The bud grows and reaches the size of the mother individual, only then separates from it (Hydra, yeast fungi, sucking ciliates)
Vegetative - characteristic of many groups of plants, a new individual develops either from special structures or from part of the mother individual.
Some multicellular animals also have vegetative reproduction (sponges, starfish, flatworms)
Sexual reproduction
Characteristic:
1.2 organizations participate
2. germ cells are involved
3. children turn out to be diverse
4. in evolutionary terms it appeared later than asexual
5. occurs under unfavorable conditions
Biological significance:
1. offspring are better adapted to changing environmental conditions and are more viable
2. new organisms arise
Pathogenesis (virgin reproduction)
Daughter organisms develop from unfertilized eggs.
The meaning of pathogenesis:
1. Reproduction is possible with rare contacts of organisms of different sexes
2. Necessary for maximizing numbers in populations with high mortality
3. For a seasonal increase in numbers in some populations
1. Obligate (obligatory) - found in populations where only female individuals (Caucasian rock lizard)
2. Cyclic (seasonal) - characteristic of aphids, plankton, daphnia, found in populations that hysterically die out in a certain season.
3. Facultative (not obligatory) - found in social insects. Males emerge from unfertilized eggs, and worker insects emerge from fertilized eggs.
Development of germ cells
Gametogenesis
Gametes are sex cells that fuse to form a zygote from which a new organism develops.
Difference between somatic cells and germ cells:
1 gametes carry a haploid set of chromosomes, and somatic ones carry a diploid
2. gametes do not divide, but somatic ones do
3. gametes, especially eggs larger than somatic cells
Gametogenesis is the formation of germ cells that occur in the gonads-genads (ovaries, testes)
Oogenesis is gametogenesis, which occurs in the female body and leads to the formation of female germ cells (ovum)
Spermatogenesis is gametogenesis, which occurs in the male body and leads to the formation of male gametes (sperm)
Gametogenesis consists of several stages:
1. Reproduction - Here, from the primary germ cells, which are called spermatogonia and oogonia, the number of future gametes increases through mitosis. Spermatogonia reproduce throughout the entire reproductive period in the male body.
In the female body, stage 1 occurs between 2 and 5 months of intrauterine development.
2. Growth - primary germ cells increase in size and turn into first-order oocytes and spermatocytes. These cells are formed in interphase. At this stage, meiosis begins.
3. Maturation - occurs in two successive divisions - reduction and equationation. As a result of the 1st division of meiosis, second-order oocytes and spermatocytes are formed; after the 2nd division of meiosis, 4 spermotids are formed from spermatocytes.
From second-order oocytes, 1 large egg and 3 reduction bodies are formed. This is due to the fact that all the energy and nutrients go towards the formation of 1 large gamete and there is not enough strength for the remaining 3 cells to form.
Therefore, 3 reduction bodies in the reproduction code are split
4. Formation - at this stage, spermatids, i.e. fully formed germ cells, grow, develop, acquire a flagellum and the shape of an adult germ cell. Spermatids are produced from spermatozoa.
Spermatozoa are formed by a head, neck and tail.
The egg is similar to a somatic cell, only it is larger in size and has additional membranes.
Fertilization
This is the process of fusion of germ cells resulting in the formation of a zygote - this is the first cell of a new organism
1. External - with this type of fertilization, the female postpones play, and the male waters her with seminal fluid. This type occurs only in aquatic environments. No special reproductive structures are required, a large amount of hereditary material is produced and the survival rate of the offspring is minimal.
2. Internal - in this type, male reproductive cells are placed in the female reproductive tract. This type requires special reproductive structures. Less hereditary material is produced. The survival rate of offspring increases. As soon as male reproductive cells enter the female’s reproductive tract, they purposefully move towards the egg, when one of the sperm penetrates the egg, its membranes become denser and it becomes inaccessible to other sperm. This is necessary to maintain the diploidity of organisms.
Double fertilization
Characteristic only for angiosperms. In the stamens, the primary male germ cells divide by meiosis, forming 4 microspores, each microspore is again divided into 2 cells (vegetative and generative)
These cells are covered with a double membrane, forming a pollen grain
In the pistil, 1 megaspore is formed from the primary female cell by meiosis and 3 cells die. The resulting megaspore is still divided into 2 cells, 1 occupies a central place in the spore, and 2 goes down
The pollen grain lands on the stigma of the pistil, the vegetative cell germinates, forming a pollen tube until the ovary. The generative cell descends through this tube, and it divides into 2 sperm. 1 sperm fertilizes the central cell from which the endosperm is formed.
2 sperm fertilize the second cell from which the embryo develops.
Ontogenesis
This is the individual development of the zygote (organism) until its death. The term was established in 1866 by Ernest Haeckel
In mammals, otnogenesis is regulated by the nervous and endocrine systems
1. Larval - in this type, emerging from the egg shells, the organism remains at the larval stage for some period, then undergoes metamorphosis (transformation into an adult)
2. Oviparous - with this type of development, the organism remains in the egg membranes for a long time and there is no larval stage
3. Intrauterine - here the development of the body takes place inside the mother’s body
Periods of ontogenesis:
1. Embryonic (intrauterine) from conception to birth
2. Postembryonic - from birth to death
Embryonic period
3 stages of development
1. Crushing
Begins a few hours after fertilization. Here the zygote begins to divide mitotically into 2 cells (blastomeres). These cells do not diverge and do not grow. Then these cells divide again and form 4 cells, and this continues until 32 cells are formed, until a morula is formed - this is an embryo consisting of 32 small cells resembling a raspberry and the size of a zygote.
This morula descends along the oviduct into the uterine cavity and implants into its wall. This occurs 6 hours after fertilization.
Then the morula cells continue to divide and a blastula is formed - this is an embryo consisting of several hundred cells located in 1 layer. The blastula has a cavity and its size is the same as that of the zygote
2. Gastrulation
Contains blastula and gastrula
The blastula continues to divide and at one end cell division is more intense. This leads to the invagination of these cells into the blastula, i.e. a gastrula is formed
The gastrula is a two-layer embryo with a primary mouth, which in mammals and higher organisms during development turns into the anus. And the true mouth is formed at the other end. The gastrula cavity is the primary cell.
The outer layer of cells is the ectoderm (1 germ layer)
The inner layer of cells is endoderm (2 pack sheets)
Then, between the ectoderm and endoderm, 3 germ layers (mesoderm) are formed symmetrically at both ends of the primary mouth.
3.Organogenesis
At this stage, the neurula is formed; on the dorsal part of the embryo, the outer layer of cells forms a groove, which closes and forms the neural tube. In parallel with this process, the intestinal tube is formed from the endoderm. And from the mesoderm the notochord is formed. The nervous system and sensory organs, as well as the mortuary epithelium and its derivatives (hair, nails) are formed from the ectoderm.
endoderm - forms the digestive system and digestive glands, the respiratory system, and the thyroid gland.
4. Mesoderm
The musculoskeletal system, circulatory, excretory, and reproductive systems are formed.
Postembryonic period
Postembryonic development can go in two ways:
Direct and indirect: with complete and incomplete transformation
Direct development is typical for birds, fish, mammals, and humans. A new individual, when born and emerging from the egg shells, is similar to an adult individual, but small in size, with different proportions, with an underdeveloped nervous and reproductive system, and the integument may also differ.
During postembryonic development, the nervous and reproductive systems further develop. The cover changes and the body undergoes training and education.
Indirect development - with this type, the larval stage is present in postembryonic development. The larva bears little or no resemblance to the adult. She grows intensively, develops and eats a lot of food.
With this type of indirect development, the organism, emerging from the egg, goes through the stage of a larva, which will turn into a pupa and the larva will completely collapse into organic compounds from which a new organism will be built. An adult individual (imago) emerges from the pupa.
egg-larva-pupa-imago
Amphibians and some insects develop with incomplete transformation
There is no pupa here and metamorphosis occurs during the larval stage.
Egg-larva-adult
26. The position of man with the system of the animal world.
Remember!
What is metabolism?
(from the Greek μεταβολή - “transformation, change”), or metabolism - a set of chemical reactions that occur in a living organism to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to environmental influences.
What two interrelated processes does it consist of?
Energy metabolism and plastic metabolism
Where in the human body is the breakdown of most of the organic substances coming from food?
Initially, in the digestive tract, then in cells and their organelles (mitochondria, cytoplasm).
Review questions and assignments
1. What is dissimilation? List its stages.
The set of reactions of the breakdown of high-molecular compounds, which are accompanied by the release and storage of energy, is called energy exchange or dissimilation. Energy is mainly stored in the form of a universal energy-intensive compound - ATP.
1) Preparatory
2) Oxygen-free oxidation
3) Oxygen oxidation
2. What is the role of ATP in cell metabolism?
Adenosine triphosphoric acid (ATP) is a nucleotide consisting of a nitrogenous base (adenine), ribose sugar and three phosphoric acid residues (Fig. 53). ATP is the main energy molecule of the cell, a kind of energy accumulator. All processes in living organisms that require energy expenditure are accompanied by the conversion of the ATP molecule into ADP (adenosine diphosphoric acid). When the phosphoric acid residue is eliminated, a large amount of energy is released - 40 kJ/mol. There are two such high-energy (so-called high-energy) bonds in the ATP molecule. The restoration of the ATP structure from ADP and phosphoric acid occurs in mitochondria and is accompanied by energy absorption.
3. What cell structures carry out ATP synthesis?
Mitochondria
4. Tell us about energy metabolism in a cell using the example of the breakdown of glucose.
1) The preparatory stage of the breakdown of carbohydrates occurs in the digestive tract to a simple carbohydrate - glucose, while little energy is released and it is dissipated in the body in the form of heat.
2) The oxygen-free stage of glucose breakdown is glycolysis (anaerobic oxidation). The stage takes place in the cytoplasm in the absence of free oxygen. Glucose C6H12O6 pyruvic acid (PVA) C3H4O3. Glucose is broken down into PVK with the release of 4ATP. 2ATP is then used in this step to further convert PVA into lactic acid. And as a result, in the second stage, 2ATP is released.
3) Oxygen oxidation – aerobic oxidation (or cellular respiration). The stage as a result of which lactic acid is broken down under the influence of molecular oxygen to the final decomposition products - carbon dioxide and water. Occurs in mitochondria on the respiratory chain of enzymes, which are located on the cristae of mitochondria. As a result of this stage, 36 ATP is released. Thus, in two stages - with complete oxidation of 1 mole of glucose (1 molecule), 38 ATP (2ATP + 36ATP) is released. The final synthesis and reserve of ATP is carried out in mitochondria - these organelles are called the energy centers of the cell.
6. Synonyms for the words “dissimilation” and “assimilation” are the terms “catabolism” and “anabolism”. Explain the origin of these terms.
Catabolism (from the Greek Καταβολή, “dumping, destruction”) or energy metabolism, or dissimilation is the process of metabolic decay, decomposition into simpler substances (differentiation) or oxidation of any substance, usually occurring with the release of energy in the form of heat and in the form ATP. Anabolism (from the Greek ἀναβολή, “rise”) is the name given to all processes of creating new substances, cells and tissues of the body. Examples of anabolism: synthesis of proteins and hormones in the body, creation of new cells, accumulation of fat, creation of new muscle fibers - this is all anabolism.
Think! Remember!
Since in cells all organic compounds are connected to each other by the main metabolites (PVC, acetyl-CoA) through which some organic substances can be converted in excess into others. For example, excess carbohydrates turn into fats.
The energy that is released during energy metabolism goes to processes in plastic metabolism. And substances of plastic metabolism are broken down in energy metabolism.
3. Why do you think that after hard physical work, in order to quickly relieve muscle pain, it is recommended to take a warm bath?
Muscle pain causes the accumulation of lactic acid during glycolysis, its concentration acts on the receptors, irritating them, causing a burning sensation. To remove this effect, a rush of blood with oxygen is necessary, oxygen to break down lactic acid into the final breakdown products. One way is to take a warm bath. At the same time, the body warms up, the vessels dilate and blood with oxygen flows and nourishes all the muscles, thereby lactic acid is oxidized to carbon dioxide and water, pain in the muscles is relieved.
