The living are open systems as they are. Living systems are considered open because they
"Conducting an open lesson" - General discussion. Needed to complement the teacher's analysis. The teacher's answers to questions about the lesson project. Lesson analysis by the teacher. Presentation of the lesson project by the teacher. Why do you need this preparatory work? Conducting an open lesson. Final generalization of the teacher. The teacher's answers to questions from those present.
"Open Reading Lesson" - Already in 1037 in Ancient Rus The library was founded by Yaroslav the Wise. Now - 65th place. At present, only 40% of 14 - year - old citizens of Russia read works of fiction. Happy reading! Until the middle of the twentieth century, our country was the most reading country in the world. Jim Corbett - Kumaon cannibals Ivan Efremov - On the edge of the Oycumene Mikhail Bulgakov - Heart of a Dog Konstantin Paustovsky - Meshcherskaya side.
Open English Lesson - Pig brags that he knows everything about animals. Tom 7 can run, jump. Decipher the pictures. Lesson topic: "In the magic forest" "In the magic forest". Help Peter introduce the artists.
"Open Lesson" - Organizational Testing Main Final Reflexive. Keep track of the pace and timing of your class. Get in the know, start something. Determine the required didactic, demonstration, handouts and equipment. Consider the activities of students at different stages of the lesson.
"Open lesson" - The purpose of the open lesson. Evaluation of the effectiveness of an open lesson. "Zest" in the lesson. Public lesson -… Preparation for the open lesson. Criteria for evaluating an open lesson. Good grade Praise Teacher's smile The joy of solving a difficult problem on your own. "Moment of joy" in the lesson. For whom?
"Open reading lesson, grade 2" - To make an act - draw up an act (document). Read it right. Green Hychechka Bump Bump The tooth is pouring out The tooth is falling out. Speech therapist. Cheerful Kind Fair Inquisitive. Check yourself! Find mistakes in words. Open lesson on reading in grade 2. Victor Yuzefovich Dragunsky (1913-1972). Which figure best reflects the mood of the story?
Course "Pedagogical theory for the modern teacher"
CURRICULUM PLAN
Newspaper number |
Educational material |
Lecture number 1. Didactics as a universal tool of pedagogical creativity |
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Lecture number 2. Contents biological education in modern conditions and its composition |
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Lecture number 3. Teaching methods, their specificity. |
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Lecture number 4. Problematic learning in biology lessons |
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Lecture number 5. Project activities. |
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Lecture number 6. Structure and types of lessons |
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Lecture number 7. Intellectual and moral development in biology lessons |
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Lecture number 8. Methodological aspects of science in biology lessons |
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The final work is the development of the lesson. |
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Lecture number 6. Structure and types of lessons
Lesson structure; types and types of lessons; lesson planning
This lecture is devoted to what, it would seem, every teacher knows from the first days of initiation into pedagogical science. And even earlier, while studying at school, each of us could intuitively evaluate the lesson taught by the teacher: interesting - uninteresting, good - bad, meaningful - not meaningful, emotionally indifferent, effective - to no avail. Such assessments of a lesson given by students can in fact be translated into didactic categories. Every teacher has an intuitive sense of what a good lesson should be. However, to build genuinely good lesson intuition is not enough. In order for the teacher's activity to be successful, he must use modern theoretical ideas and pedagogical technologies.
What is a lesson? Here is one of the most common classifications of lesson types.
1. Lesson in learning new material.
2. Lesson in the formation of knowledge, abilities, skills.
3. The lesson of consolidation and development of knowledge, abilities, skills.
4. Lesson repetition.
5. Lesson to check knowledge.
6. Lesson in the application of knowledge, skills and abilities.
7. Repetitive and generalizing lesson.
8. Combined lesson.
Many innovative teachers offer their own classifications of lessons. So, L.V. Malakhova classifies the lessons as follows.
1. An overview story on the whole topic.
2. Lesson of student questions and additional clarifications.
3. Lesson - practical work.
4. The lesson is of a generalized type with task cards that focus on the selection and assimilation of the main elements of the educational material.
5. Final survey on theoretical material.
6. Solving problems on the topic.
The system developed by N.P. Guzik, includes the following types of lessons.
1. Lessons of theoretical analysis of the material by the teacher.
2. Lessons for self-analysis of the topic by students (divided into groups) according to the given plans, algorithms.
3. Lessons-seminars.
4. Lessons-workshops.
5. Lessons in the control and assessment of knowledge.
There are quite a few classifications of types and types of lessons, and each teacher can give preference to one of them or take something different from each. It is only important to understand for what purposes you conduct a certain type of lesson and how you organize the assimilation of the educational material. It is also important to correlate the features of the content that must be learned in this lesson, with the capabilities of the students and with the methods and forms of organizing the lesson.
I invite you to analyze and classify two versions of the lesson on the topic "Introduction to General Biology" in the 10th grade using the textbook by D.K. Belyaeva, A.O. Ruvinsky and others.
Lesson option 1. Lesson type - lesson in learning new material
Lesson plan and structure
1. Organizational moment.
2. Initial introduction of the material.
3. Emphasis on the main points of the topic.
4. Creation of motivation for memorizing the material.
5. Demonstration of memorization techniques.
6. Initial consolidation of the material by repetition.
According to this plan, the teacher will define the concept of "General biology", then list the main properties of life, explaining the most difficult terminological and conceptual elements of the topic, then move on to the levels of organization of life and give their brief description. In conclusion, he will talk about research methods in biology and its significance. In the process of presenting the material, the teacher will show the basic memorization techniques, paying attention to what should be remembered, and will give a test, for example, in the form of test tasks.
Task (option 1)
1. The subject of study of general biology is:
a) the structure and functions of the body;
b) natural phenomena;
c) patterns of development and functioning of living systems;
d) the structure and functions of plants and animals.
2. Choose the most correct statement:
a) only living systems are built from complex molecules;
b) all living systems have high degree organizations;
c) living systems differ from non-living systems chemical elements;
d) in inanimate nature the high complexity of the organization of the system is not encountered.
3. The most low level living systems exhibiting the ability to exchange substances, energy, information is:
a) biosphere;
b) molecular;
c) organismic;
d) cellular.
4. The highest level of organization of life is:
a) biosphere;
b) biogeocenotic;
c) population-specific;
d) organismic.
5. The main scientific method in the most early period the development of biology was:
a) experimental;
b) microscopy;
c) comparative historical;
d) the method of observing and describing objects.
Task (option 2)
Choose the correct statements.
1. All living organisms:
a) have an equally complex level of organization;
b) have a high level of metabolism;
c) react in the same way to the environment;
d) have the same mechanism for the transmission of hereditary information.
2. Living systems are considered open because they:
a) formed from the same chemical elements as inanimate systems;
b) exchange matter, energy and information with the external environment;
c) have the ability to adapt;
d) are able to reproduce.
3. The level at which interspecies relationships begin to manifest themselves is called:
a) biogeocenotic;
b) population-specific;
c) organismic;
d) biospheric.
4. The most common feature of all biological systems:
a) the complexity of the structure of the system;
b) the laws operating at each level of the development of the system;
c) the elements that make up the system;
d) the qualities possessed by this system.
5. The first superorganic level includes:
a) cell colony;
b) forest biocenosis;
c) the population of hares;
d) gopher.
This form is quite legal for this type of lessons. Students will partially understand the general ideas of the topic, remember the basic terms, will be able (though not all) to answer the questions of the assignment, and thus the goal set - to ensure the primary assimilation of material in general biology - will be largely achieved. However, it is worth considering how effective such a lesson on this topic is. Is it not possible to create a different composition and achieve greater results than a partial understanding of the topic and fixing some terms in memory?
Let's try to give a lesson on the same topic and using the same material, but using a different logic. Its main goal is to motivate students to self-study new material with the means at their disposal. In connection with the goal, the lesson plan and its logic are also changing, new techniques are used, unexpected for students.
Lesson option 2. Lesson type - lesson in learning new material
Lesson outline
1. Statement of the problem: how does general biology differ from the sciences studied before?
2. Invite students to carefully read the two versions of test items.
3. Try to briefly formulate the answer to the question: what will be discussed in the lesson? (This activity will not be completed at this point in the lesson.)
4. If students are having difficulty, explain to them that they should not look for the correct answers in the assignment. Their goal is to find out the subject of discussion, to try to identify the main ideas and problems of the topic. Discuss search results.
5. After 10-15 minutes of joint work, give the children the correct answers to the questions of the assignments and ask them to state in writing (or orally) the answer to the question posed earlier.
6. After listening to several options for an answer, pay attention to its logic. The questions in the test tasks are not built in accordance with the logic of the presentation of the material in the textbook, and the students, naturally, build their answer by listing the correct answers to the tasks.
7. Ask to build an answer in accordance with the logic of the content of the educational material, which is revealed during the conversation on this task.
8. Students correct the answer and then write an essay on the topic: "What does general biology study?"
9. After completing the assignment, work begins with the textbook: the text written by the students is compared with the text of the textbook. By discovering the similarities between these texts, schoolchildren experience a true state of success.
10. Discussion of the main substantive elements of the topic: the concept of "biological system", properties and levels of life organization, research methods.
11. Solving the problem of the lesson: general biology studies the patterns of functioning and development of living systems at different levels. Botany, zoology, anatomy are more special sciences that study mainly the organismal and partly supraorganic levels.
What is the advantage of building this lesson? In the light of what was said in the previous lectures, the answer is clear: in the organization of the assimilation of educational material, i.e. in teaching methods. After all, if the first version of the lesson assumed only two types of student activity - cognitive (primary cognition) and reproductive (exercises), then the second option also activates creative activity, and immediately, at the very first lesson of the course, and with active motivation. Doesn't a purposeful analysis of an unfamiliar text, selection of the necessary conceptual apparatus, a combination of selected concepts and phrases into a coherent text require the manifestation of creative abilities? In addition, each student's learning action is accompanied by internal reflection: “Did I do it right or wrong? Does what I have chosen have anything to do with the answer to the question? Will my answer match the text of the textbook or not? " Consequently, this form of presentation of educational material creates motivation to work with it.
The result of the lesson is the product of one's own search - written or spoken text, well-understood and assimilated material, the acquired ability to initially operate with new concepts.
These examples of lessons on one topic are polar. There are other options for presenting the material and organizing the assimilation. You can modify the content and structure of the lesson. You can start the topic with the disclosure of the concept of "system", give a systemic picture of the world, compare living and nonliving systems, etc. The point is not only and not so much in the content, although it is important, but in how the activities of the teacher and students are organized: and what the students will do in order for some of the proposed content to become the property of their personality. Moreover, each of the senior pupils can be "assigned" his own part, which will become a part of his education. But on the other hand, almost all students in the class will assimilate the invariant part of the content, and all students will work at all levels of assimilation - cognitive, reproductive, creative.
Let's go back to the classification of the lessons. In the book of A.V. Kuleva “General biology. Lesson planning ”lists 4 types of lessons and several of their types. The types of lessons suggested by the author are included in the list at the beginning of the lecture. But the types of lessons, or rather the forms of organization of educational activities, it makes sense to cite, although many of them are included in the integrated scheme of the learning process in lecture No. 1. Here is the list.
1. Lesson-reflection.
2. Lesson - "travel".
3. Lesson-judgment.
4. Lesson game.
5. Lesson-round table.
6. Integrated lesson.
7. Lesson-dispute.
8. Lesson conference.
9. Lesson research.
10. Lesson-excursion.
When planning a particular form of lesson, it is necessary to ask the same question: how will the students' activities be organized? An example is a court lesson in the form of a performance. This is an interesting lesson form that will make a great impression on children. But if, some time after such a lesson, you ask the students questions on the topic studied, you will be surprised to notice that the answers of some of them, even the participants in the performance, leave much to be desired. In this case, it is worth considering whether you did the right thing to write the play and stage it yourself? Maybe you should have puzzled the guys with this idea? And then, albeit for the sake of the quality of the text (although it is not at all necessary), several effects could be achieved - fun, creative educational, and not just the performing participation of children. And the audience could be not only spectators, but also designers and musicians, and at the same time interested students. There is a lot of room here for all sorts of ideas and discoveries. It is only important that the fascinating form does not harm knowledge and that the passivity of the participants in the process does not hide behind the external design.
IN last years a variety of teaching technologies are developing (read, for example, the book by G.K. Selevko "Modern educational technologies"). By acquaintance with the conceptual foundations of technologies, with their methodological features, the teacher can ensure the assimilation of the same material in a variety of ways and techniques. So, for example, the topic "Breathing" in the course "Human" can be given in a traditional way, explaining and consolidating the material. And in the context of cooperation pedagogy, this topic can begin to unfold with the joint construction of various breathing models, having previously studied the literature and discussed possible models. Using the technology of V.F. Shatalov, you can apply supporting notes, etc. You can use both individual and group forms of work, role-playing and business games, use various types of visualization - tables, films, demonstrations. All this will have a definite effect only when the teacher predicts the students' activities at almost every moment of the lesson. Therefore, when planning a lesson, you should consider the following points.
1. What is the cognitive significance of the topic of the lesson?
2. What types of activities can be foreseen and planned in this lesson? What will the student do at each moment of the lesson?
3. What is the place of this lesson in the lesson system?
4. How can the students' knowledge and skills be updated to master this topic?
5. What additional sources of information does this topic of the lesson allow to use and whether it should be done in the lesson.
6. How will the technical training aids be used? It is not necessary to apply them unless necessary.
7. What are the types and levels of difficulty of tasks that you propose for consolidation, independent search and control (self-control)?
In the fragments of lessons given in this and other lectures, you can find the provisions that are discussed in this part of the lecture. So, when planning the lesson "Monohybrid crossing", it is necessary to realize its theoretical, indicative and evaluative significance. It is important to provide for the connection of this lesson with the previous (section "Reproduction") and with subsequent topics ("Evolution", "Selection"). It is quite obvious that the topic of this lesson presupposes the possibility of organizing the assimilation of the material both by the reproductive method and by the methods of problem study - problem presentation, heuristic conversation. Actualization of existing knowledge can be written or oral in the form of a system of questions, test tasks, solving problems on the topics "Mitosis" and "Meiosis". A movie fragment or the same biblical text can be used as additional sources of information. For the first lesson on the topic, this is enough. Other teaching aids in this lesson are dynamic models, table, computer model. The tasks offered to students in this lesson can be either simple, requiring reproduction, or quite complex. For example, you can propose a problem that requires the calculation of various options for the possible inheritance of a particular trait. It all depends on what kind of didactic material the teacher has. Of course, it is important to calculate how long such an activity will take. It may happen that one lesson is not enough to fully study the material. This means that you need to give two lessons and you should not be afraid of deviations from the curriculum. There is knowledge and skills, for the formation and development of which it is necessary to spend more time than it is planned curriculum... Do not be afraid of this, because the time spent will more than pay off in the future.
Questions and tasks for independent work
1. What are the main differences between the lessons on the topic "Introduction to General Biology" given in the lecture?
2. Why is it important to identify links between this lesson and previous and subsequent topics?
3. Come up with several different-level assignments for any of the topics of the course.
A living organism is a complex systemcomposed of interconnected organs and tissues. But why do they say that the body is an open system? Open systems are characterized by the exchange of something with their external environment. It can be an exchange of matter, energy, information. And living organisms exchange all this with the outside world for them. Although the word "exchange" is more appropriate to replace the word "flow", since some substances and energy enter the body, while others leave.
Energy is absorbed by living organisms in one form (plants - in the form of solar radiation, animals - in the chemical bonds of organic compounds), and is released into the environment in another (thermal). Since the body receives energy from the outside and releases it, it is an open system.
In heterotrophic organisms, energy is absorbed together with the substances (in which it is contained) as a result of nutrition. Further, in the process of metabolism (metabolism within the body), some substances are broken down, while others are synthesized. During chemical reactions, energy is released (going to various life processes) and energy is absorbed (going to the synthesis of the necessary organic matter). Substances unnecessary for the body and the resulting heat energy (which can no longer be used) are released into the environment.
Autotrophs (mainly plants) absorb light rays as energy in a certain range, and as initial substances they absorb water, carbon dioxide, various mineral salts, and oxygen. Using energy and these minerals, plants, as a result of the process of photosynthesis, carry out the primary synthesis of organic substances. In this case, radiant energy is stored in chemical bonds. Plants have no excretory system. However, they release substances with their surface (gases), dropping foliage (harmful organic and mineral substances are removed), etc. Thus, plants as living organisms are also open systems. They release and absorb substances.
Living organisms live in their characteristic habitat. At the same time, in order to survive, they must adapt to the environment, react not to its changes, look for food and avoid the threat. As a result, in the process of evolution, animals have developed special receptors, sense organs, and the nervous system, which make it possible to receive information from the external environment, process it and react, that is, to influence the environment. Thus, we can say that organisms exchange information from external habitats. That is, an organism is an open information system.
Plants also respond to environmental influences (for example, they close their stomata in the sun, turn the leaves towards light, etc.). In plants, primitive animals and fungi, regulation is carried out only by chemical means (humoral). In animals with nervous system, there are both ways of self-regulation (nervous and with the help of hormones).
Single-celled organisms are also open systems. They feed and secrete substances, react to external influences. However, in their body-system, the functions of organs are essentially performed by cellular organelles.
CHAPTER 1. PROPERTIES AND ORIGIN OF LIFE1.1. SUBJECT, PROBLEMS AND METHODS OF BIOLOGY
Biology (Greek bio - life and logos - knowledge, teaching, science) - the science of living organisms. The diversity of living nature is so great that modern biology is a complex of sciences (biological sciences), significantly different from one another. Moreover, each has its own subject of study, methods, goals and objectives. For example, virology is the science of viruses, microbiology is the science of microorganisms, mycology is the science of fungi, botany (phytology) is the science of plants, zoology is the science of animals, anthropology is the science of man, cytology is the science of cells, histology is science. about tissues, anatomy is the science of internal structure, morphology is the science of external structure, physiology - the science of the vital activity of an integral organism and its parts, genetics - the science of the laws of heredity and variability of organisms and methods of managing them, ecology - the science of the relationship of living organisms between themselves and their environment, the theory of evolution - the science of the historical development of living nature, paleontology is the science of the development of life in past geological times, biochemistry is the science of chemicals and processes in living organisms; biophysics is the science of physical and physicochemical phenomena in living organisms, biotechnology is a set of industrial methods that make it possible to use living organisms and their individual parts for the production of products valuable for humans (amino acids, proteins, vitamins, enzymes, antibiotics, hormones, etc.) etc.
Biology belongs to the complex of natural sciences, that is, the sciences of nature. It is closely related to the fundamental sciences (mathematics, physics, chemistry), natural (geology, geography, soil science), social (psychology, sociology), applied (biotechnology, crop production, nature conservation).
Biological knowledge is used in food Industry, pharmacology, agriculture. Biology is theoretical basis such sciences as medicine, psychology, sociology.
Advances in biology should be used in solving global problems modernity: the relationship of society with the environment, rational nature management and nature protection, food security.
Biological research methods:
Method of observation and description (consists in collecting and describing facts);
comparative method (consists in analyzing the similarities and differences of the objects under study);
historical method (studies the course of development of the object under study);
experimental method (allows you to study natural phenomena under specified conditions);
modeling method (allows complex natural phenomena to be described with relatively simple models).
1.2. PROPERTIES OF LIVING MATTER
Domestic scientist M.V. Volkenstein proposed the following definition: "Living bodies that exist on Earth are open, self-regulating and self-reproducing systems built of biopolymers - proteins and nucleic acids."
However, there is no generally accepted definition of the concept of "life", but signs (properties) of living matter that distinguish it from inanimate matter can be distinguished.
1. Certain chemical composition. Living organisms consist of the same chemical elements as objects of inanimate nature, however, the ratio of these elements is different. The main elements of living things are C, O, N and N.
2.Cellular structure. All living organisms, except for viruses, have a cellular structure.
3. Metabolism and energy dependence. Living organisms are open systems, they depend on the supply of substances and energy from the external environment.
4. Self-regulation. Living organisms have the ability to maintain the constancy of their chemical composition and the intensity of metabolic processes.
5. Irritability and mental function. Living organisms show irritability, that is, the ability to respond to certain external influences with specific reactions.
6. Heredity. Living organisms are able to transmit traits and properties from generation to generation using information carriers - DNA and RNA molecules.
7. Variability. Living organisms are capable of acquiring new characteristics and properties.
8.Self reproduction (reproduction). Living organisms are able to reproduce - reproduce their own kind.
9.Individual development. Ontogenesis is the development of an organism from the moment of inception to death. Development is accompanied by growth.
10. Evolutionary development. Phylogenesis is the development of life on Earth from the moment of its origin to the present.
11. Rhythm. Living organisms show the rhythm of life (daily, seasonal, etc.), which is associated with the characteristics of the habitat.
12. Integrity and discreteness. On the one hand, all living matter is integral, organized in a certain way and obeys general laws; on the other hand, any biological system consists of isolated, albeit interconnected, elements.
13. Hierarchy. From biopolymers (nucleic acids, proteins) to the biosphere as a whole, all living things are in a certain subordination. The functioning of biological systems at a less complex level makes it possible for a more complex level to exist (see next paragraph).
1.3. LEVELS OF LIVING NATURE
The hierarchy of the organization of living matter makes it possible to conditionally subdivide it into a number of levels. The level of organization of living matter is a functional place of the biological structure of a certain degree of complexity in the general hierarchy of living matter. The following levels are distinguished:
1.Molecular (molecular genetic). At this level, such vital processes are manifested as metabolism and energy conversion, transmission of hereditary information.
2.Cellular. The cell is an elementary structural and functional unit of living things.
3.Tissue. Tissue is a set of structurally similar cells, as well as intercellular substances associated with them, united by the performance of certain functions.
4. Organ. An organ is a part of a multicellular organism that performs a specific function or functions.
5.Organic. An organism is a real bearer of life, characterized by all its characteristics. Currently, a single "ontogenetic" level is often distinguished, including cellular, tissue, organ and organismal levels organizations.
6. Population-specific. Population - a set of individuals of one species, forming a separate genetic system and inhabiting a space with relatively homogeneous living conditions. A species is a set of populations, individuals of which are capable of interbreeding with the formation of fertile offspring and occupy a certain area of \u200b\u200bgeographic space (range).
7. Biocenotic. Biocenosis - a set of organisms of different types of varying complexity of organization, living in a certain area. If the abiotic factors of the environment are also taken into account, then they speak of biogeocenosis.
8. Biospheric. The biosphere is the shell of the Earth, the structure and properties of which to one degree or another are determined by the present or past activity of living organisms. It should be noted that the biosphere level of organization of living matter is often not distinguished, since the biosphere is a bioinert system that includes not only living matter, but also inanimate matter.
1.4. ORIGIN OF LIFE
On the question of the origin of life, as well as on the question of the essence of life, there is no consensus among scientists. There are several approaches to solving the issue of the origin of life, which are closely intertwined. They can be classified as follows.
1. According to the principle that the idea, mind are primary, and matter is secondary (idealistic hypotheses) or matter is primary, and the idea, mind are secondary (materialistic hypotheses).
2. According to the principle that life has always existed and will exist forever (hypothesis of a stationary state), or life arises at a certain stage in the development of the world.
3. According to the principle - living only from living (hypothesis of biogenesis) or spontaneous generation of living from non-living (hypothesis of abiogenesis) is possible.
4. According to the principle, life arose on Earth or was brought from space (hypothesis of panspermia).
Let's consider the most significant of the hypotheses.
Creationism. Life was created by the Creator. The Creator is God, Idea, Higher Mind, or others.
Stationary hypothesis. Life, like the Universe itself, has always existed and will exist forever, for that which has no beginning has no end. At the same time, the existence of individual bodies and formations (stars, planets, organisms) is limited in time, they arise, are born and die. At present, this hypothesis is mainly of historical significance, since the generally accepted theory of the formation of the Universe is "the theory Big bang", according to which the Universe exists for a limited time, it was formed from one point about 15 billion years ago.
Panspermia hypothesis. Life was brought to Earth from space, and took root here, after favorable conditions developed on Earth. The solution to the question of how life arose in space, due to the objective difficulties of its solution, is postponed indefinitely. It could be created by the Creator, always exist, or arise from inanimate matter. Recently, more and more supporters of this hypothesis have appeared among scientists.
Hypothesis of abiogenesis (spontaneous generation of living from non-living and subsequent biochemical evolution). Life originated on Earth from inanimate matter.
In 1924 A.I. Oparin suggested that living things arose on Earth from inanimate matter as a result of chemical evolution - complex chemical transformations of molecules. This event was favored by the conditions prevailing at that time on Earth.
In 1953 S. Miller obtained a number of organic substances from inorganic compounds under laboratory conditions. The fundamental possibility of an inorganic pathway for the formation of biogenic organic compounds (but not living organisms) was proved.
A.I. Oparin believed that organic matter could be created in the primary ocean from simple inorganic compounds. As a result of the accumulation of organic matter in the ocean, the so-called "primary soup" was formed. Then, combining, proteins and other organic molecules formed drops of coacervates, which served as the prototype of cells. Drops of coacervates were exposed natural selection and evolved. The first organisms were heterotrophic. As the reserves of the "primary broth" were depleted, autotrophs arose.
It should be noted that from the point of view of the theory of probability, the probability of the synthesis of supercomplex biomolecules, provided that their constituent parts are randomly combined, is extremely low.
IN AND. Vernadsky about the origin and essence of life and the biosphere. IN AND. Vernadsky outlined his views on the origin of life in the following theses:
1. There was no beginning of life in the cosmos that we observe, since there was no beginning of this cosmos. Life is eternal, since the cosmos is eternal, and has always been transmitted by biogenesis.
2. Life, which is eternally inherent in the Universe, appeared new on Earth, its embryos were brought from outside all the time, but were strengthened on Earth only with favorable opportunities for this.
3. Life on Earth has always been. The lifetime of a planet is only the lifetime of life on it. Life is geologically (planetary) eternal. The age of the planet is indeterminate.
4. Life has never been something random, huddled in some separate oases. It was distributed everywhere and always living matter existed in the form of the biosphere.
5. The most ancient forms of life - scraps - are capable of performing all functions in the biosphere. This means that a biosphere is possible, consisting of some prokaryotes. It is likely that this is how it was in the past.
6. Living substance could not come from inert. There are no intermediate steps between these two states of matter. On the contrary, as a result of the impact of life, the evolution of the earth's crust took place.
Thus, it is necessary to recognize the fact that to date, none of the existing hypotheses about the origin of life has direct evidence, and modern science there is no definite answer to this question.
CHAPTER 2. CHEMICAL COMPOSITION OF LIVING ORGANISMS
2.1. ELEMENTAL COMPOSITION
The chemical composition of living organisms can be expressed in two forms: atomic and molecular. The atomic (elemental) composition characterizes the ratio of the atoms of the elements that make up living organisms. Molecular (material) composition reflects the ratio of molecules of substances.
According to the relative content, the elements that make up living organisms are usually divided into three groups:
1. Macronutrients - H, O, C, N (about 98% in total, they are also called basic), Ca, Cl, K, S, P, Mg, Na, Fe (about 2% in total). Macronutrients make up the bulk of the percentage of living organisms.
2. Microelements - Mn, Co, Zn, Cu, B, I, etc. Their total content in the cell is about 0.1%.
3. Ultramicroelements - Au, Hg, Se, etc. Their content in the cell is very insignificant, and the physiological role for most of them is not disclosed.
Chemical elements that are part of living organisms and at the same time perform biological functions are called biogenic. Even those of them, which are contained in cells in negligible quantities, cannot be replaced by anything and are absolutely necessary for life.
2.2. MOLECULAR COMPOSITION
Chemical elements are part of cells in the form of ions and molecules of inorganic and organic substances. The most important inorganic substances in the cell are water and mineral salts, the most important organic substances are carbohydrates, lipids, proteins and nucleic acids.
2.2.1. Inorganic substances
2.2.1.1. Water
Water is the predominant component of all living organisms. It has unique properties due to its structural features: water molecules are dipole-shaped and hydrogen bonds are formed between them. The average water content in the cells of most living organisms is about 70%. Water in the cell is present in two forms: free (95% of all cell water) and bound (4-5% bound to proteins).
Water functions:
1. Water as a solvent. Many chemical reactions in the cell are ionic, therefore they occur only in aquatic environment... Substances that dissolve in water are called hydrophilic (alcohols, sugars, aldehydes, amino acids), insoluble - hydrophobic (fatty acids, cellulose).
2. Water as a reagent. Water participates in many chemical reactions: polymerization reactions, hydrolysis, in the process of photosynthesis.
3. Transport function. Moving through the body, together with water, substances dissolved in it to its various parts and removing unnecessary products from the body.
4. Water as a thermostabilizer and thermostat. This function is due to such properties of water as high heat capacity - it softens the effect on the body of significant temperature changes in the environment; high thermal conductivity - allows the body to maintain the same temperature throughout its entire volume; high heat of vaporization - used to cool the body during perspiration in mammals and transpiration in plants.
5. Structural function. The cytoplasm of cells contains from 60 to 95% water, and it is this that gives the cells their normal shape. In plants, water maintains turgor (elasticity of the endoplasmic membrane), in some animals it serves as a hydrostatic skeleton (jellyfish).
2.2.1.2. Mineral salts
Mineral salts in an aqueous solution of the cell dissociate into cations and anions. The most important cations are K +, Ca2 +, Mg2 +, Na +, NH4 +, anions are Cl-, SO42-, HPO42-, H2PO4-, HCO3-, NO3-. Not only the concentration, but also the ratio of individual ions in the cell is essential.
Functions of minerals:
1. Maintenance of acid-base balance. The most important buffer systems in mammals are phosphate and bicarbonate. Phosphate buffer system (HPO42-, H2PO4-) maintains the pH of the intracellular fluid within 6.9-7.4. The bicarbonate system (HCO3-, H2CO3) maintains the pH of the extracellular medium (blood plasma) at 7.4.
2. Participation in the creation of membrane potentials of cells. Inside the cell, K + ions and large organic ions predominate, and in the pericellular fluids there are more Na + and Cl- ions. As a result, a difference in charges (potentials) of the outer and inner surfaces of the cell membrane is formed. The potential difference makes it possible to transmit excitation along a nerve or muscle.
3.Activation of enzymes. Ions Ca2 +, Mg2 +, etc. are activators and components of many enzymes, hormones and vitamins.
4. Creation of osmotic pressure in the cell. A higher concentration of salt ions inside the cell ensures the flow of water into it and the creation of turgor pressure.
5.Construction (structural). Compounds of nitrogen, phosphorus, calcium and other inorganic substances serve as a source of building material for the synthesis of organic molecules (amino acids, proteins, nucleic acids, etc.) and are part of a number of supporting structures of the cell and organism. Calcium and phosphorus salts are part of the bone tissue of animals.
2.2.2. Organic matter
The concept of biopolymers. A polymer is a multi-link chain in which a link is a relatively simple substance - a monomer. Biological polymers are polymers that make up the cells of living organisms and their metabolic products. Biopolymers are proteins, nucleic acids, polysaccharides.
2.2.2.1. Carbohydrates
Carbohydrates are organic compounds made up of one or many molecules of simple sugars. The carbohydrate content in animal cells is 1-5%, and in some plant cells it reaches 70%. There are three groups of carbohydrates: monosaccharides (or simple sugars), oligosaccharides (consist of 2-10 molecules of simple sugars), polysaccharides (consist of more than 10 sugar molecules).
Monosaccharides are ketone or aldehyde derivatives of polyhydric alcohols. Depending on the number of carbon atoms, trioses, tetroses, pentoses (ribose, deoxyribose), hexoses (glucose, fructose) and heptoses are distinguished. Depending on the functional group, sugars are divided into: aldoses, which have an aldehyde group (glucose, ribose, deoxyribose), and ketose, which have a ketone group (fructose).
Oligosaccharides in nature are mostly represented by disaccharides, consisting of two monosaccharides linked to each other through a glycosidic bond. The most commonly found maltose, or malt sugar, is made up of two glucose molecules; lactose, which is part of milk and consists of galactose and glucose; sucrose, or beet sugar, including glucose and fructose.
Polysaccharides. In polysaccharides, simple sugars (glucose, mannose, galactose, etc.) are interconnected by glycosidic bonds. If only 1-4 glycosidic bonds are present, then a linear, unbranched polymer (cellulose) is formed; if both 1-4 and 1-6 bonds are present, the polymer will be branched (glycogen).
Cellulose is a linear polysaccharide composed of β-glucose molecules. Cellulose is the main component of the plant cell wall. Starch and glycogen, branched polymers from β-glucose residues, are the main forms of glucose storage in plants and animals, respectively. Chitin forms the outer skeleton (shell) in crustaceans and insects, and in fungi it gives strength to the cell wall.
Functions of carbohydrates:
1.Energy. When simple sugars (primarily glucose) are oxidized, the body receives the bulk of the energy it needs. With the complete breakdown of 1 g of glucose, 17.6 kJ of energy is released.
2.Storage. Starch and glycogen act as a source of glucose, releasing it as needed.
3.Construction (structural). Cellulose and chitin impart strength to the cell walls of plants and fungi, respectively. Ribose and deoxyribose are part of the nucleic acids.
4.Receptor. The function of recognition by cells of each other is provided by glycoproteins that make up cell membranes... The loss of the ability to recognize each other is characteristic of malignant tumor cells.
2.2.2.2. Lipids
Lipids are fats and fat-like organic compounds that are practically insoluble in water. Their content in different cells varies greatly: from 2-3 to 50-90% in the cells of plant seeds and adipose tissue of animals. Chemically, lipids are usually esters of fatty acids and a number of alcohols. They are divided into several classes: neutral fats, waxes, phospholipids, steroids, etc.
Lipid functions:
1.Construction (structural). Phospholipids, together with proteins, are the basis of biological membranes. Cholesterol is an important component of animal cell membranes.
2. Hormonal (regulatory). Many hormones chemical nature are steroids (testosterone, progesterone, cortisone).
3.Energy. When 1 g of fatty acids is oxidized, 38 kJ of energy is released and twice as much ATP is synthesized as when the same amount of glucose is broken down.
4.Storage. A significant part of the body's energy reserves is stored in the form of fats. In addition, fats serve as a source of water (when 1 g of fat is burned, 1.1 g of water is formed). This is especially valuable for desert and arctic animals lacking free water.
5. Protective. In mammals, subcutaneous fat acts as a thermal insulator. Wax covers the epidermis of plants, feathers, wool, animal hair, protecting it from wetting.
6. Participation in metabolism. Vitamin D plays a key role in calcium and phosphorus metabolism.
2.2.2.3. Protein
Proteins are biological heteropolymers, the monomers of which are amino acids.
In terms of chemical composition, amino acids are compounds containing one carboxyl group (-COOH) and one amine group (-NH2), linked to one carbon atom to which a side chain is attached - some radical R (it is he who gives the amino acid its unique properties) ...
Only 20 amino acids are involved in the formation of proteins. They are called fundamental or basic: alanine, methionine, valine, proline, leucine, isoleucine, tryptophan, phenylalanine, asparagine, glutamine, serine, glycine, tyrosine, threonine, cysteine, arginine, histidine, lysine, aspartic and glutamic acids. Some of the amino acids are not synthesized in the organisms of animals and humans and must come from plant foods (they are called essential).
Amino acids, connecting with each other by covalent peptide bonds, form peptides of various lengths. A peptide (amide) bond is a covalent bond formed by the carboxyl group of one amino acid and the amine group of another. Proteins are high molecular weight polypeptides containing from one hundred to several thousand amino acids.
There are 4 levels of protein organization:
Primary structure is a sequence of amino acids in a polypeptide chain. It is formed by covalent peptide bonds between amino acid residues. The primary structure is determined by the sequence of nucleotides in the region of the DNA molecule that encodes a given protein. The primary structure of any protein is unique and determines its shape, properties and function.
The secondary structure is formed by the folding of polypeptide chains into an α-helix or β-structure. It is supported by hydrogen bonds between the hydrogen atoms of the NH- groups and the oxygen atoms of the CO- groups. -helix is \u200b\u200bformed as a result of the twisting of the polypeptide chain into a helix with equal distances between the turns. It is characteristic of globular proteins that have a spherical globule shape. β-structure is a longitudinal folding of three polypeptide chains. It is characteristic of fibrillar proteins with an elongated fibril shape. Only globular proteins have tertiary and quaternary structures.
The tertiary structure is formed when the helix coils into a coil (globule, or domain). Domains are globular-like formations with a hydrophobic core and a hydrophilic outer layer. The tertiary structure is formed due to the bonds formed between the radicals of R amino acids, due to ionic, hydrophobic and dispersion interactions, as well as due to the formation of disulfide (S-S) bonds between cysteine \u200b\u200bradicals.
The quaternary structure is characteristic of complex proteins consisting of two or more polypeptide chains not linked by covalent bonds, as well as for proteins containing non-protein components (metal ions, coenzymes). The quaternary structure is supported by the same chemical bonds as the tertiary.
The configuration of a protein depends on the sequence of amino acids, but it can also be influenced by the specific conditions in which the protein is located.
The loss of a protein molecule of its structural organization is called denaturation. Denaturation can be reversible and irreversible. With reversible denaturation, the quaternary, tertiary and secondary structures are destroyed, but due to the preservation of the primary structure when normal conditions return, protein renaturation is possible - restoration of the normal (native) conformation.
By chemical composition, simple and complex proteins are distinguished. Simple proteins are composed only of amino acids (fibrillar proteins, immunoglobulins). Complex proteins contain a protein part and a non-protein part - prosthetic groups. Distinguish between lipoproteins (contain lipids), glycoproteins (carbohydrates), phosphoproteins (one or more phosphate groups), metalloproteins (various metals), nucleoproteins (nucleic acids). Prosthetic groups usually play an important role in the protein's biological function.
Protein functions:
1.Catalytic (enzymatic). All enzymes are proteins. Proteins-enzymes catalyze the course in the body chemical reactions.
2.Construction (structural). It is carried out by fibrillar proteins keratins (nails, hair), collagen (tendons), elastin (ligaments).
3.Transportation. A number of proteins are capable of attaching and carrying various substances (hemoglobin carries oxygen).
4. Hormonal (regulatory). Many hormones are protein substances (insulin regulates glucose metabolism).
5. Protective. Blood immunoglobulins are antibodies; fibrin and thrombin are involved in blood clotting.
6. Contractile (motor). Actin and myosin form microfilaments and carry out muscle contraction, tubulin forms microtubules.
7.Receptor (signal). Some proteins embedded in the membrane "receive information" from the environment.
8.Energy. When 1 g of protein is broken down, 17.6 kJ of energy is released.
Enzymes. Proteins-enzymes catalyze the course of chemical reactions in the body. These reactions, due to energetic reasons, either do not occur in the body at all, or proceed too slowly.
By their biochemical nature, all enzymes are high molecular weight protein substances, usually of a quaternary structure. All enzymes contain non-protein components in addition to protein. The protein part is called an apoenzyme, and the non-protein part is called a cofactor (if it is a simple inorganic substance, for example, Zn2 +) or a coenzyme (coenzyme) (if it is an organic compound).
The enzyme molecule has an active center, consisting of two sections - sorption (responsible for binding the enzyme to the substrate molecule) and catalytic (responsible for the actual catalysis). In the course of the reaction, the enzyme binds the substrate, sequentially changes its configuration, forming a number of intermediate molecules that ultimately give the reaction products.
The difference between enzymes and catalysts of an inorganic nature is as follows:
1. One enzyme catalyzes only one type of reaction.
2. The activity of enzymes is limited by a rather narrow temperature range (usually 35-45 ° C).
3. Enzymes are active at certain pH values \u200b\u200b(most in a slightly alkaline environment).
2.2.2.4. Nucleic acids
Mononucleotides. A mononucleotide consists of one purine (adenine - A, guanine - G) or pyrimidine (cytosine - C, thymine - T, uracil - U) nitrogenous base, sugar pentose (ribose or deoxyribose) and 1-3 phosphoric acid residues.
Polynucleotides. There are two types of nucleic acids: DNA and RNA. Nucleic acids are polymers whose monomers are nucleotides.
DNA and RNA nucleotides are composed of the following components:
1.Nitrogen base (in DNA: adenine, guanine, cytosine and thymine; in RNA: adenine, guanine, cytosine and uracil).
2. Sugar pentose (in DNA - deoxyribose, in RNA - ribose).
3. Residue of phosphoric acid.
DNA (deoxyribonucleic acids) is a long-chain unbranched polymer consisting of four types of monomers - nucleotides A, T, G, and C - linked to each other by a covalent bond through phosphoric acid residues.
A DNA molecule consists of two spirally twisted strands (double helix). In this case, adenine forms 2 hydrogen bonds with thymine, and guanine - 3 bonds with cytosine. These pairs of nitrogenous bases are called complementary. In the DNA molecule, they are always opposite each other. The chains in the DNA molecule are oppositely directed. The spatial structure of the DNA molecule was established in 1953 by D. Watson and F. Crick.
By binding to proteins, the DNA molecule forms a chromosome. A chromosome is a complex of one DNA molecule with proteins. The DNA molecules of eukaryotic organisms (fungi, plants, and animals) are linear, unclosed, linked to proteins, forming chromosomes. In prokaryotes (bacteria), DNA is closed in a ring, not bound to proteins, and does not form a linear chromosome.
Function of DNA: storage, transmission and reproduction in a number of generations of genetic information. DNA determines which proteins and in what quantities need to be synthesized.
RNA (ribonucleic acids) contain ribose instead of deoxyribose, and uracil instead of thymine. RNAs usually have only one strand, shorter than DNA strands. Double-stranded RNAs are found in some viruses.
RNA types:
Informational (messenger) RNA - mRNA (or mRNA). Has an open circuit. Serves as templates for protein synthesis, transferring information about their structure from the DNA molecule to the ribosomes into the cytoplasm.
Transport RNA - tRNA. Delivers amino acids to the synthesized protein molecule. The tRNA molecule consists of 70-90 nucleotides and due to intrachain complementary interactions it acquires a characteristic secondary structure in the form of a "clover leaf".
Ribosomal RNA - rRNA. In combination with ribosomal proteins, it forms ribosomes - organelles on which protein synthesis occurs.
In a cell, mRNA accounts for about 5%, tRNA - about 10%, and rRNA - about 85% of all cellular RNA.
RNA functions: participation in protein biosynthesis.
Self-doubling of DNA. DNA molecules have an ability that no other molecule has — the ability to duplicate. The process of doubling DNA molecules is called replication. Replication is based on the principle of complementarity - the formation of hydrogen bonds between nucleotides A and T, G and C.
This process is carried out by DNA polymerase enzymes. Under their influence, the chains of the DNA molecule are separated on a small segment of the molecule. Daughter chains are completed on the chain of the parent molecule. Then a new segment is unwound and the replication cycle is repeated.
As a result, daughter DNA molecules are formed, which are no different from each other and from the parent molecule. In the process of cell division, daughter DNA molecules are distributed between the resulting cells. This is how information is transmitted from generation to generation.
CHAPTER 3. STRUCTURE OF THE CELL
The main provisions of the cell theory:
1. The cell is a structural unit of all living things. All living organisms are composed of cells (with the exception of viruses).
2. The cell is a functional unit of all living things. The cell exhibits the full range of vital functions.
3. The cell is the unit of development of all living things. New cells are formed only as a result of division of the original (mother) cell.
4. The cell is the genetic unit of all living things. The chromosomes of a cell contain information about the development of the whole organism.
5. The cells of all organisms are similar in chemical composition, structure and function.
3.1. TYPES OF CELL ORGANIZATION
Among living organisms, only viruses do not have a cellular structure. All other organisms are represented by cellular life forms. There are two types of cellular organization: prokaryotic and eukaryotic. Bacteria and blue-greens belong to prokaryotes, plants, fungi and animals are to eukaryotes.
The structure of prokaryotic cells is relatively simple. They do not have a nucleus, the area of \u200b\u200bDNA in the cytoplasm is called a nucleoid, the only DNA molecule is circular and is not associated with proteins, the cells are smaller than eukaryotic cells, the glycopeptide - murein is part of the cell wall, membrane organelles are absent, their functions are performed by invaginations of the plasma membrane, ribosomes are small, microtubules are absent, therefore the cytoplasm is immobile, and the cilia and flagella have a special structure.
Eukaryotic cells have a nucleus in which chromosomes are located - linear DNA molecules associated with proteins; various membrane organelles are located in the cytoplasm.
Plant cells are distinguished by the presence of a thick cellulose cell wall, plastids, and a large central vacuole that displaces the nucleus to the periphery. Cell center higher plants does not contain centrioles. The storage carbohydrate is starch.
Fungal cells have a cell membrane containing chitin, there is a central vacuole in the cytoplasm, and there are no plastids. Only a few fungi have a centriole in the cell center. The main reserve carbohydrate is glycogen.
Animal cells, as a rule, have a thin cell wall, do not contain plastids and a central vacuole; the centriole is characteristic of the cell center. The storage carbohydrate is glycogen.
3.2. THE STRUCTURE OF THE EUKARYOTIC CELL
All cells are made up of three main parts:
1. The cell membrane limits the cell from the environment.
2. The cytoplasm is the inner content of the cell.
3. Nucleus (in prokaryotes - nucleoid). Contains the genetic material of the cell.
3.2.1. Cell membrane
The structure of the cell wall. The basis of the cell membrane is the plasma membrane - a biological membrane that limits the internal contents of the cell from the external environment.
All biological membranes are a double layer of lipids, the hydrophobic ends of which face inward, and the hydrophilic heads, outward. Proteins are immersed in it at various depths, some of which penetrate the membrane through and through. Proteins are able to move in the plane of the membrane. Membrane proteins perform different functions: transport of various molecules; receiving and converting signals from the environment; maintenance of membrane structure. The most important property of membranes is selective permeability.
Plasma membranes of animal cells have a glycocalyx layer outside, consisting of glycoproteins and glycolipids, and performing signaling and receptor functions. It plays an important role in the union of cells into tissues. Plasma membranes of plant cells are covered with a cellulose cell wall. The pores in the wall allow water to pass through and small molecules, and rigidity provides the cage with mechanical support and protection.
Functions of the cell wall. The cell membrane performs the following functions: determines and maintains the shape of the cell; protects the cell from mechanical stress and penetration of damaging biological agents; delimits the internal contents of the cell; regulates the metabolism between the cell and the environment, ensuring the constancy of the intracellular composition; carries out the recognition of many molecular signals (for example, hormones); participates in the formation of intercellular contacts and various kinds of specific protrusions of the cytoplasm (microvilli, cilia, flagella).
The mechanisms of penetration of substances into the cell. There is a constant exchange of matter between the cell and the environment. Ions and small molecules are transported across the membrane by passive or active transport, macromolecules and large particles - by endo- and exocytosis.
Passive transport - the movement of a substance along a concentration gradient, carried out without energy consumption, by simple diffusion, osmosis or facilitated diffusion using carrier proteins. Active transport - the transfer of a substance by carrier proteins against a concentration gradient, is associated with energy costs.
Endocytosis is the absorption of substances by surrounding them with outgrowths of the plasma membrane with the formation of vesicles surrounded by a membrane. Exocytosis is the release of substances from a cell by surrounding them with outgrowths of the plasma membrane with the formation of vesicles surrounded by a membrane. The absorption and release of solid and large particles are respectively called phagocytosis and reverse phagocytosis, liquid or dissolved particles - pinocytosis and reverse pinocytosis.
3.2.2. Cytoplasm
The cytoplasm is the internal contents of the cell and consists of the main substance (hyaloplasm) and various intracellular structures (inclusions and organelles) located in it.
Hyaloplasm (matrix) is an aqueous solution of inorganic and organic substances that can change its viscosity and is in constant motion.
The cytoplasmic structures of the cell are represented by inclusions and organelles. Inclusions are unstable structures of the cytoplasm in the form of granules (starch, glycogen, proteins) and drops (fats). Organoids are permanent and indispensable components of most cells that have a specific structure and perform vital functions.
Single-membrane cell organelles: endoplasmic reticulum, lamellar Golgi complex, lysosomes.
Endoplasmic reticulum (reticulum) is a system of interconnected cavities, tubes and channels, delimited from the cytoplasm by one membrane layer and dividing the cytoplasm of cells into isolated spaces. This is necessary to separate many parallel reactions. A rough endoplasmic reticulum is distinguished (on its surface ribosomes are located on which protein is synthesized) and a smooth endoplasmic reticulum (lipids and carbohydrates are synthesized on its surface).
The Golgi apparatus (lamellar complex) is a stack of 5-20 flattened disc-shaped membrane cavities and microbubbles detached from them. Its function is transformation, accumulation, transport of substances entering it to various intracellular structures or outside the cell. The membranes of the Golgi apparatus are capable of forming lysosomes.
Lysosomes are membrane vesicles containing lytic enzymes. In lysosomes, both the products entering the cell by endocytosis and the constituent parts of the cells or the whole cell (autolysis) are digested. Distinguish between primary and secondary lysosomes. Primary lysosomes are microbubbles detached from the cavities of the Golgi apparatus, surrounded by a single membrane and containing a set of enzymes. After the fusion of the primary lysosomes with the substrate to be cleaved, secondary lysosomes are formed (for example, the digestive vacuoles of protozoa).
Vacuoles are membrane bags filled with liquid. The membrane is called tonoplast, and the contents are called cell sap. The cell sap may contain reserve nutrients, pigment solutions, waste products, and hydrolytic enzymes. Vacuoles are involved in the regulation of water-salt metabolism, the creation of turgor pressure, the accumulation of reserve substances and the elimination of toxic compounds from the metabolism.
The endoplasmic reticulum, the Golgi complex, lysosomes and vacuoles are one-membrane structures and form a single membrane system of the cell.
Two-membrane cell organelles: mitochondria and plastids.
In eukaryotic cells, there are also organelles isolated from the cytoplasm by two membranes. These are mitochondria and plastids. They have their own circular DNA molecule, small ribosomes and are able to divide. This served as the basis for the emergence of the symbiotic theory of the emergence of eukaryotes. According to this theory, in the past, mitochondria and plastids were independent prokaryotes, which later moved on to endosymbiosis with other cellular organisms.
Mitochondria are rod-shaped, oval or rounded organelles. The content of mitochondria (matrix) is limited from the cytoplasm by two membranes: an outer smooth and an inner one that forms folds (cristae). ATP molecules are formed in the mitochondria.
Plastids are organelles surrounded by a membrane consisting of two membranes, with a homogeneous substance inside (stroma). Plastids are characteristic only for cells of photosynthetic eukaryotic organisms. Depending on the color, chloroplasts, chromoplasts and leukoplasts are distinguished.
Chloroplasts are green plastids in which the process of photosynthesis takes place. The outer membrane is smooth. Internal - forms a system of flat bubbles (thylakoids), which are collected in stacks (granules). The thylakoid membranes contain the green pigments chlorophyll, as well as carotenoids. Chromoplasts are plastids containing carotenoid pigments that give them red, yellow and orange colors. They give bright colors to flowers and fruits. Leukoplasts are unpigmented, colorless plastids. Contained in the cells of underground or unpainted parts of plants (roots, rhizomes, tubers). They are able to accumulate reserve nutrients, primarily starch, lipids and proteins. Leukoplasts can turn into chloroplasts (for example, during flowering of potato tubers), and chloroplasts - into chromoplasts (for example, during fruit ripening).
Organoids that do not have a membrane structure: ribosomes, microfilaments, microtubules, cell center.
Ribosomes are small globular organelles composed of proteins and rRNA. Ribosomes are represented by two subunits: large and small. They can either be free in the cytoplasm, or attach to the endoplasmic reticulum. Protein synthesis occurs on ribosomes.
Microtubules and microfilaments are filamentous structures consisting of contractile proteins and determining the motor functions of the cell. Microtubules look like long hollow cylinders, the walls of which are composed of proteins - tubulins. Microfilaments are even thinner, longer, filamentous structures composed of actin and myosin. Microtubules and microfilaments permeate the entire cytoplasm of a cell, forming its cytoskeleton, cause cyclosis (cytoplasmic flow), intracellular movements of organelles, form a division spindle, etc. Microtubules, organized in a certain way, form the centrioles of the cell center, basal bodies, cilia, flagella.
The cell center (centrosome) is usually located near the nucleus, consists of two centrioles located perpendicular to each other. Each centriole has the form of a hollow cylinder, the wall of which is formed by 9 triplets of microtubules. Centrioles play an important role in cell division, forming the division spindle.
Flagella and cilia are organelles of movement, which are peculiar outgrowths of the cytoplasm of the cell. The skeleton of the flagellum or cilium has the form of a cylinder, along the perimeter of which there are 9 paired microtubules, and in the center - 2 single ones.
3.2.3. Core
Most cells have one nucleus, but multinucleated cells are also found (in a number of protozoa, in the skeletal muscles of vertebrates). Some highly specialized cells lose their nuclei (mammalian erythrocytes and sieve tube cells in angiosperms).
The nucleus is usually spherical or oval in shape. The nucleus includes the nuclear envelope and the karyoplasm, which contains chromatin (chromosomes) and nucleoli.
The nuclear envelope is formed by two membranes (outer and inner). The holes in the nuclear envelope are called nuclear pores. Through them, the exchange of matter between the nucleus and the cytoplasm is carried out.
Karyoplasm is the inner content of the nucleus.
Chromatin is an uncoiled DNA molecule associated with proteins. As such, DNA is present in non-dividing cells. In this case, DNA duplication (replication) and the implementation of the information contained in the DNA are possible. Chromosome is a coiled DNA molecule associated with proteins. DNA is coiled before cell division to more accurately distribute genetic material during division. At the metaphase stage, each chromosome consists of two chromatids, which are the result of DNA duplication. Chromatids are interconnected in the area of \u200b\u200bthe primary constriction, or centromere. The centromere divides the chromosome into two arms. Some chromosomes have secondary constrictions.
The nucleolus is a spherical structure, the function of which is the synthesis of rRNA.
Functions of the nucleus: 1. Storage of genetic information and its transfer to daughter cells in the process of division. 2. Control of cell activity.
CHAPTER 4. EXCHANGE OF SUBSTANCES AND ENERGY CONVERSION
4.1. FOOD TYPES OF LIVING ORGANISMS
All living organisms living on Earth are open systems that depend on the supply of matter and energy from the outside. The process of consuming matter and energy is called nutrition. Chemicals are necessary for building the body, energy - for the implementation of vital processes.
According to the type of nutrition, living organisms are divided into autotrophs and heterotrophs.
Autotrophs are organisms that use carbon dioxide as a carbon source (plants and some bacteria). In other words, these are organisms capable of creating organic substances from inorganic ones - carbon dioxide, water, mineral salts.
Depending on the energy source, autotrophs are divided into phototrophs and chemotrophs. Phototrophs are organisms that use light energy for biosynthesis (plants, cyanobacteria). Chemotrophs are organisms that use the energy of chemical reactions of oxidation of inorganic compounds for biosynthesis (chemotrophic bacteria: hydrogen, nitrifying, iron bacteria, sulfur bacteria, etc.).
Heterotrophs are organisms that use organic compounds as a carbon source (animals, fungi, and most bacteria).
According to the method of obtaining food, heterotrophs are divided into phagotrophs (holozoi) and osmotrophs. Phagotrophs (holozoi) swallow solid pieces of food (animals), osmotrophs absorb organic matter from solutions directly through the cell walls (fungi, most bacteria).
Mixotrophs are organisms that can both synthesize organic substances from inorganic ones and feed on ready-made organic compounds (insectivorous plants, representatives of the department of euglena algae, etc.).
Table 1 shows the type of nutrition of large systematic groups of living organisms.
Table 1
Types of nutrition of large systematic groups of living organisms
4.2. CONCEPT OF METABOLISM
Metabolism is the totality of all chemical reactions occurring in a living organism. The importance of metabolism is to create the substances necessary for the body and provide it with energy. There are two components of metabolism - catabolism and anabolism.
Catabolism (or energy metabolism, or dissimilation) is a set of chemical reactions leading to the formation of simple substances from more complex ones (hydrolysis of polymers to monomers and the splitting of the latter to low-molecular compounds of carbon dioxide, water, ammonia, and other substances). Catabolic reactions usually occur with the release of energy.
Anabolism (or plastic metabolism, or assimilation) is the opposite of catabolism - a set of chemical reactions for the synthesis of complex substances from simpler ones (the formation of carbohydrates from carbon dioxide and water during photosynthesis, matrix synthesis reactions). For anabolic reactions to take place, energy is required.
The processes of plastic and energy exchange are inextricably linked. All synthetic (anabolic) processes require energy supplied during dissimilation reactions. The very same reactions of cleavage (catabolism) proceed only with the participation of enzymes synthesized in the process of assimilation.
4.3. ATP AND ITS ROLE IN METABOLISM
The energy released during the breakdown of organic substances is not immediately used by the cell, but is stored in the form of high-energy compounds, usually in the form of adenosine triphosphate (ATP).
ATP (adenosine triphosphoric acid) is a mononucleotide consisting of adenine, ribose and three phosphoric acid residues connected by high-energy bonds. Energy is stored in these bonds, which is released when they are broken:
ATP + H2O -\u003e ADP + H3PO4 + Q1
ADP + H2O -\u003e AMP + H3PO4 + Q2
AMP + H2O -\u003e adenine + ribose + H3PO4 + Q3,
Where ATP is adenosine triphosphoric acid; ADP - adenosine diphosphoric acid; AMP - adenosine monophosphoric acid; Q1 \u003d Q2 \u003d 30.6 kJ; Q3 \u003d 13.8 kJ.
The supply of ATP in the cell is limited and is replenished through the process of phosphorylation. Phosphorylation is the addition of the phosphoric acid residue to ADP (ADP + F ATP). The energy stored in ATP molecules is used by the body in anabolic reactions (biosynthesis reactions). The ATP molecule is a universal storage and carrier of energy for all living beings.
4.4. ENERGY EXCHANGE
The energy necessary for life, most organisms receive as a result of the oxidation of organic substances, that is, as a result of catabolic reactions. The most important compound that acts as a fuel is glucose.
In relation to free oxygen, organisms are divided into three groups.
Aerobes (obligate aerobes) are organisms that can live only in an oxygen environment (animals, plants, some bacteria and fungi).
Anaerobes (obligate anaerobes) are organisms that are unable to live in an oxygen environment (some bacteria).
Facultative forms (facultative anaerobes) are organisms that can live both in the presence of oxygen and without it (some bacteria and fungi).
In obligate aerobes and facultative anaerobes in the presence of oxygen, catabolism proceeds in three stages: preparatory, anoxic, and oxygen. As a result, organic substances decompose to inorganic compounds. In obligate anaerobes and facultative anaerobes, with a lack of oxygen, catabolism proceeds in the first two stages: preparatory and anoxic. As a result, intermediate organic compounds are formed, which are still rich in energy.
Stages of catabolism:
1. The first stage - preparatory - consists in the enzymatic cleavage of complex organic compounds into simpler ones. Proteins are broken down to amino acids, fats to glycerol and fatty acids, polysaccharides to monosaccharides, nucleic acids to nucleotides. In multicellular organisms, this occurs in the gastrointestinal tract, in unicellular organisms - in lysosomes under the action of hydrolytic enzymes. The released energy is dissipated in the form of heat. The formed organic compounds either undergo further oxidation, or are used by the cell to synthesize its own organic compounds.
2. The second stage - incomplete oxidation (oxygen-free) - consists in the further decomposition of organic substances, carried out in the cytoplasm of the cell without the participation of oxygen.
Anoxic, incomplete oxidation of glucose is called glycolysis. As a result of glycolysis of one glucose molecule, two molecules of pyruvic acid (PVA, pyruvate) CH3COCOOH, ATP and water are formed, as well as hydrogen atoms, which are bound by the NAD + carrier molecule and stored in the form of NADTH.
The total formula for glycolysis is as follows:
C6H12O6 + 2 H3PO4 + 2 ADP + 2 NAD + -\u003e 2 C3H4O3 + 2 H2O + 2 ATP + 2 NADTH.
In the absence of oxygen in the environment, glycolysis products (PVC and NADTH) are processed either into ethyl alcohol - alcoholic fermentation (in yeast and plant cells with a lack of oxygen)
CH3COCOOH -\u003e СО2 + СН3СОН
CH3SON + 2 NADTH -\u003e C2H5OH + 2 NAD +,
Or into lactic acid - lactic acid fermentation (in animal cells with a lack of oxygen)
CH3COCOOH + 2 NADTH C3H6O3 + 2 OVER +.
In the presence of oxygen in the environment, the products of glycolysis undergo further degradation to final products.
3. The third stage - complete oxidation (respiration) - consists in the oxidation of PVC to carbon dioxide and water, carried out in the mitochondria, with the obligatory participation of oxygen.
It consists of three stages:
A) the formation of acetylcoenzyme A;
B) oxidation of acetyl coenzyme A in the Krebs cycle;
C) oxidative phosphorylation in the electron transport chain.
A. At the first stage, PVC is transferred from the cytoplasm to the mitochondria, where it interacts with matrix enzymes and forms: 1) carbon dioxide, which is removed from the cell; 2) hydrogen atoms, which are delivered by carrier molecules to the inner membrane of the mitochondrion; 3) acetyl coenzyme A (acetyl-CoA).
B. At the second stage, acetyl coenzyme A is oxidized in the Krebs cycle. The Krebs cycle (tricarboxylic acid cycle, citric acid cycle) is a chain of sequential reactions during which one acetyl-CoA molecule is formed: 1) two molecules of carbon dioxide, 2) an ATP molecule, and 3) four pairs of hydrogen atoms transferred to molecules - carriers - NAD and FAD.
Thus, as a result of glycolysis and the Krebs cycle, the glucose molecule is split to CO2, and the released energy is spent on the synthesis of 4ATP and accumulates in 10NADTH and 4FADTH2.
C. At the third stage, hydrogen atoms with NADTH and FADTH2 are oxidized by molecular oxygen O2 with the formation of water. One NADTH is capable of forming 3 ATP, and one FADTH2 - 2 ATP. Thus, the energy released during this is stored in the form of another 34 ATP. The production of ATP in mitochondria with the participation of oxygen is called oxidative phosphorylation.
Thus, the total equation for the breakdown of glucose in the process of cellular respiration is as follows:
C6H12O6 + 6 O2 + 38 H3PO4 + 38 ADP -\u003e 6 CO2 + 44 H2O + 38 ATP.
Thus, during glycolysis, 2 ATP molecules are formed, during cellular respiration, another 36 ATP, in general, with complete oxidation of glucose - 38 ATP.
4.5. PLASTIC EXCHANGE
4.5.1. Photosynthesis
Photosynthesis is the synthesis of organic compounds from inorganic ones due to the energy of light. The overall equation of photosynthesis:
6 CO2 + 6 H2O -\u003e C6H12O6 + 6 O2.
Photosynthesis takes place with the participation of photosynthetic pigments, which have a unique property of converting energy sunlight into energy chemical bond in the form of ATP. The most important pigment is chlorophyll.
The process of photosynthesis consists of two phases: light and dark.
(1) The light phase of photosynthesis occurs only in the light in the grana thylakoid membrane. It includes: absorption of light quanta by chlorophyll, photolysis of water and the formation of an ATP molecule.
Under the influence of a quantum of light (hv), chlorophyll loses electrons, passing into an excited state:
Hv
chl -\u003e chl * + e-.
These electrons are transferred by carriers to the outer, that is, the matrix-facing surface of the thylakoid membrane, where they accumulate.
At the same time, photolysis of water occurs inside the thylakoids, that is, its decomposition under the action of light
Hv
2 H2O -\u003e O2 +4 H + + 4 e-.
The resulting electrons are transferred by carriers to chlorophyll molecules and reduce them. Chlorophyll molecules return to a stable state.
Hydrogen protons formed during photolysis of water accumulate inside the thylakoid, creating an H + reservoir. As a result, the inner surface of the thylakoid membrane is charged positively (due to H +), and the outer surface - negatively (due to e-). As oppositely charged particles accumulate on both sides of the membrane, the potential difference increases. When the critical value of the potential difference is reached, the strength of the electric field begins to push protons through the ATP synthetase channel. The energy released in this case is used for phosphorylation of ADP molecules. The production of ATP during photosynthesis under the influence of light energy is called photophosphorylation.
Hydrogen ions, being on the outer surface of the thylakoid membrane, meet there with electrons and form atomic hydrogen, which binds to the hydrogen carrier molecule NADP (nicotinamide adenine dinucleotide phosphate):
2 H + + 4- + NADP + -\u003e NADPTH2.
Thus, during the light phase of photosynthesis, three processes occur: the formation of oxygen due to the decomposition of water, the synthesis of ATP, and the formation of hydrogen atoms in the form of NADPTH2. Oxygen diffuses into the atmosphere, and ATP and NADPTH2 participate in the dark phase processes. 2. The dark phase of photosynthesis occurs in the chloroplast matrix both in the light and in the dark and is a series of sequential transformations of CO2 coming from the air in the Calvin cycle. The reactions of the dark phase are carried out due to the energy of ATP. In the Calvin cycle, CO2 binds with hydrogen from NADPTH2 to form glucose.
In the process of photosynthesis, in addition to monosaccharides (glucose, etc.), monomers of other organic compounds are synthesized - amino acids, glycerol and fatty acids.
4.5.2. Chemosynthesis
Chemosynthesis (chemoautotrophy) is the process of synthesizing organic compounds from inorganic (CO2, etc.) due to the chemical energy of oxidation of inorganic substances (sulfur, hydrogen sulfide, iron, ammonia, nitrite, etc.).
Only chemosynthetic bacteria are capable of chemosynthesis: nitrifying, hydrogen, iron bacteria, sulfur bacteria, etc. They oxidize compounds of nitrogen, iron, sulfur and other elements. All chemosynthetics are obligate aerobes, since they use atmospheric oxygen.
The energy released during oxidation reactions is stored by bacteria in the form of ATP molecules and is used for the synthesis of organic compounds, which proceeds similarly to the reactions of the dark phase of photosynthesis.
4.5.3. Protein biosynthesis
In almost all organisms, genetic information is stored in the form of a specific sequence of DNA nucleotides (or RNA in RNA-containing viruses). Prokaryotes and many viruses contain genetic information in a single DNA molecule. All of its sites encode macromolecules. In eukaryotic cells, genetic material is distributed over several DNA molecules organized into chromosomes.
Gene - a section of a DNA molecule (less often RNA) encoding the synthesis of one macromolecule: mRNA (polypeptide), rRNA or tRNA. The region of the chromosome where the gene is located is called the locus. The set of genes of the cell nucleus is the genotype, the set of genes of the haploid set of chromosomes is the genome, the set of genes of extra-nuclear DNA (mitochondria, plastids, cytoplasm) is the plasmon.
The implementation of information recorded in genes through protein synthesis is called gene expression (manifestation). Genetic information is stored as a specific sequence of DNA nucleotides, and is realized as a sequence of amino acids in a protein. RNA acts as intermediaries, carriers of information. That is, the implementation of genetic information is as follows:
DNA -\u003e RNA -\u003e protein
This process is carried out in two stages:
1) transcription;
2) broadcast.
Transcription is the synthesis of RNA using DNA as a template. The result is mRNA. The transcription process requires a lot of energy in the form of ATP and is carried out by the enzyme RNA polymerase.
At the same time, not the entire DNA molecule is transcribed, but only its individual segments. Such a segment (transcriptone) begins with a promoter - a DNA section where RNA polymerase is attached and from where transcription begins, and ends with a terminator - a DNA section containing the transcription end signal. A transcripton is a gene from the point of view of molecular biology.
Transcription, like replication, is based on the ability of nitrogenous bases of nucleotides for complementary binding. At the time of transcription, the double DNA strand is broken and RNA synthesis is carried out along one DNA strand.
In the process of translation, the DNA nucleotide sequence is rewritten to the synthesized mRNA molecule, which acts as a template in the process of protein biosynthesis.
Translation is the synthesis of a polypeptide chain using mRNA as a template.
All three types of RNA are involved in translation: mRNA is an information matrix; tRNAs deliver amino acids and recognize codons; rRNA together with proteins form ribosomes that hold mRNA, tRNA and protein and carry out the synthesis of the polypeptide chain.
The mRNA is translated not by one, but simultaneously by several (up to 80) ribosomes. Such groups of ribosomes are called polysomes. The inclusion of one amino acid in the polypeptide chain requires the energy of 4 ATP.
DNA code. Information about the structure of proteins is "recorded" in DNA as a sequence of nucleotides. In the process of transcription, it is rewritten to a synthesized mRNA molecule, which acts as a template in the process of protein biosynthesis. A certain amino acid in the polypeptide chain of a protein corresponds to a certain combination of DNA nucleotides, and, consequently, mRNA. This correspondence is called the genetic code. One amino acid is defined by 3 nucleotides combined into a triplet (codon). Since there are 4 types of nucleotides, combining 3 into a triplet, they give 43 \u003d 64 variants of triplets (while only 20 amino acids are encoded). Of these, 3 are "stop codons" that stop translation, the remaining 61 are coding. Different amino acids are encoded different numbers triplets: from 1 to 6.
Properties of the genetic code:
1. The code is triplet. One amino acid is encoded by three nucleotides (triplet) in a nucleic acid molecule.
2. The code is universal. All living organisms, from viruses to humans, use a single genetic code.
3. The code is unambiguous (specific). A codon corresponds to one single amino acid.
4. The code is redundant. One amino acid is encoded by more than one triplet.
5. The code does not overlap. One nucleotide cannot be part of several codons in a nucleic acid chain at once.
Protein synthesis steps:
(1) A small subunit of the ribosome combines with the initiator met-tRNA, and then with mRNA, after which a whole ribosome is formed, consisting of small and large subunits.
2. The ribosome moves along the mRNA, which is accompanied by multiple repetitions of the cycle of attaching the next amino acid to the growing polypeptide chain.
3. The ribosome reaches one of the three stop codons of the mRNA, the polypeptide chain is released and detached from the ribosome. Ribosomal subunits dissociate, detach from mRNA, and can take part in the synthesis of the next polypeptide chain.
Matrix synthesis reactions. Matrix synthesis reactions include: DNA self-doubling, the formation of mRNA, tRNA and rRNA on a DNA molecule, protein biosynthesis on mRNA. All these reactions are united by the fact that the DNA molecule in one case, or the mRNA molecule in the other, act as a matrix on which the formation of identical molecules occurs. Matrix synthesis reactions are the basis of the ability of living organisms to reproduce their own kind.
Http://sfedu.ru/lib1/chem/020101/m2_a_020101.htm
Option I
The method of biological science, which consists in collecting scientific facts and their research, is called:
A) modeling B) descriptive
B) historical D) experimental
A) Aristotle B) Theofast
B) Hypocrates D) Galena
The science that studies the laws of heredity and variability is called:
A) ecology B) genetics
4. The property of organisms to selectively react to external and internal influences is called:
A) self-reproduction B) metabolism and energy
B) openness D) irritability
5. The idea of \u200b\u200bthe evolution of living nature was first formulated by:
A) B) Charles Darwin
B) D) K. Linnaeus
6. The cellular level of life does not include:
A) Escherichia coli B) Poleosian psilophyte
B) bacteriophage D) nodule bacteria
7. The processes of protein breakdown under the action of gastric juice proceed at the level of life organization:
A) cellular B) small
B) organismic D) population
8. The circulation of substances and energy flows occur at the level of organization of living nature:
A) ecosystem B) population-specific
B) bispheric D) molecular
9. The cellular level of life includes:
A) tubercle bacillus B) polypeptide
10. Living systems are considered open because they:
A) are built from the same chemical elements as non-living systems
B) exchange matter, energy and information with the external environment
C) have the ability to adapt
D) are able to reproduce
Test for a generalizing lesson on the topic "Introduction" 10 cl.
Option II
General biology studies:
A) general patterns of development of living systems
B) general signs of the structure of plants and animals
C) the unity of living and inanimate nature
D) the origin of the species
2. The laws of transmission of hereditary traits are studied by science:
A) embryology B) evolutionary theory
B) fieldontology D) genetics
3. The level of organization of life, at which such a property is manifested as the ability to exchange substances, energy, information -
B) organismic D) cellular
4. The highest level of organization of life is:
A) cellular B) population-specific
B) biosphere D) organismic
5. In the early stages of the development of biology, the main method scientific research was:
A) experimental B) microscopy
B) comparative historical D) observations and descriptions of objects
6. The fact of seasonal molting in animals was established:
A) experimentally B) comparative historical
B) observation method D) modeling method
7. Interspecies relationships begin to manifest themselves at the level of:
A) biogeocenotic B) organismic
B) population-specific D) biosphere
A) Louis Pasteur B) Charles Darwin
B) K. Linnaeus D)
9. Fundamentals of cell theory:
A) G. Mendel B) T. Schwann
B) D) M. Schleider
10. Choose the correct statement:
A) only living systems are built from complex molecules
B) all living systems have a high degree of organization
C) living systems differ from non-living systems in the composition of chemical elements
D) in inanimate nature there is no high complexity of the organization of the system
Option I:
Option II:
