cell - the basic unit of all organisms.From its state depends on the degree of activity, the ability to adapt to environmental conditions.The processes of cell activity are subject to certain laws.The level of activity occurrence of each depends on the phase of the life cycle.A total of two isolated: interphase and division (M phase).The first takes the time between the formation of the cell and its destruction or division.During interphase actively proceed practically all the basic processes of cell activity: food, breathing, growth, irritability, motion.Reproduction of the cells is carried out only at the stage of M.
period of interphase
Time cell growth between divisions is divided into several stages:
- presynthetic or G-phase 1 - initial stage: the synthesis of messenger RNA, proteins, and certain other cellelements;
- synthetic or phase S: doubling of the DNA;
- postsynthetic or G-phase 2: Preparation for mitosis.
In addition, some of the cells cease to divide after differentiation.Among them there is no interphase between G-1.They are so-called resting phase (G-0).
Metabolism
As already mentioned, the vital processes of living cells for the most part take place during interphase.The main of them is the metabolism.Thanks to him, occur not only various internal reactions and intercellular processes that link individual structures in the whole organism.
metabolism has a certain scheme.The processes of cell activity is largely dependent upon compliance with it, the lack of any kind was in violation of it.Substances before affect intracellular environment, must penetrate through the membrane.Then, they are subjected to certain processing power or during respiration.In the next step the resulting by-products are used for the synthesis of new cells or transformation of existing structures.Remaining after all transformations metabolic products that are harmful to cells or simply do not need it, removed the external environment.
assimilation and dissimilation
regulation sequential shift transformation of some substances into other enzymes involved.They contribute to the more rapid the flow of specific processes, that is, act as catalysts.Each such "accelerator" affects only the specific transformation aiming for a one-way process.The newly formed substances further exposed to other enzymes that contribute to their further transformation.
Thus all processes of cell activity in one way or another connected with two opposite trends: assimilation and dissimilation.To metabolism their interaction, balance, or are the basis for a confrontation.Various substances coming from outside, is converted by enzymes in the customary and necessary for the cell.These synthetic transformations and called assimilation.In addition, for such reactions requires energy.Its source is the processes of dissimilation, or destruction.The collapse of the substance is accompanied by the release of energy needed to proceed could fundamental life processes of the cell.Dissimilation also promotes the formation of simpler compounds, which are then used for the new synthesis.Part of the decay products at the same output.
vital processes of cells are often associated with the balance of synthesis and degradation.Thus, growth is only possible with the predominance of assimilation over dissimilation.Interestingly, the infinite cell can not grow: it laid down certain limits, beyond which the growth stops.
Penetration
transporting substances from the environment into the cell is carried out passively and actively.In the first case the transfer becomes possible due to diffusion and osmosis.Active transportation is accompanied by loss of energy, and often occurs in spite of these processes.Thus, for example, potassium ions penetrate.They are injected into the cell, even if their concentration in the cytoplasm exceeds the level of the external environment.
Features substances affect the permeability of the cell membrane for them.Thus, the organic substances are released into the cytoplasm lighter than inorganic.For the permeability has a value and the size of molecules.Also, the properties of the membrane are dependent upon the physiological state of the cell and environmental characteristics such as temperature and light.
Power
The entry of substances from the environment are involved fairly well-studied processes of life: cell respiration and its food.The latter is carried via pinocytosis and fagotsitoza.Mehanizm both processes similar, but during pinocytosis entrained smaller and less dense particles.The molecules are adsorbed membrane absorbed, captured by special outgrowths and plunge with them into the cell.The result is the channel, and then emerge from the membrane vesicles containing edible particles.Gradually, they are exempt from the shell.Further, the particles are exposed to very close to the digestion process.After a series of transformations substance split into simpler and used for the synthesis of the elements necessary cell.In this part of the resulting output substances into the environment, as not subject to further processing or use.
Breath
Food - not the only process that facilitates the emergence of the necessary elements in the cell.Breathing in essence very similar to him.It is a series of successive transformations of carbohydrates, lipids and amino acids, which occur as a result of new substances: carbon dioxide and water.The most important part of the process is the formation energy, which is stored by the cell in the form of ATP and other compounds.
with oxygen
vital processes of human cells, as well as many other organisms, are inconceivable without aerobic respiration.The main substances necessary for it, is oxygen.Releasing much needed energy, and the formation of new compounds resulting from the oxidation occurs.
breathing process is divided into two stages:
-
glycolysis;
-
oxygen stage.
Glycolysis - the splitting of glucose in the cytoplasm of the cell by the action of enzymes without oxygen.It is a series of eleven successive reactions.As a result of the formation of one molecule of glucose, two molecules of ATP.The decay products at the same time fall into the mitochondria, where it begins the oxygen stage.As a result of several reactions of formed carbon dioxide, additional ATP molecules and hydrogen atoms.In general, the cell receives from one molecule of glucose 38 molecules of ATP.Because of the large amount of stored energy aerobic respiration and is considered more effective.
Anaerobic respiration
bacteria peculiar to another type of breathing.They are used instead of oxygen, sulfates, nitrates, and so forth.This type of breathing is less efficient, but it plays a huge role in the cycle of matter in nature.Due anaerobic organisms carried biogeochemical cycle of sulfur, nitrogen and sodium.In general processes are similar to oxygen breathing.After closure of glycolysis formed substance react fermentation, which could result in ethanol or lactic acid.
Irritability
cells are constantly interacting with the environment.The answer to the impact of various external factors called irritability.It is expressed in excitable cells in the transition state and the occurrence of the reaction.The type of response to the external influence is different depending on the functional characteristics.Muscle cells respond reduction cells, glands - secretions and neurons - nerve impulse generation.This irritability is the basis of many physiological processes.Thanks to her, for example, carried out nervous regulation of neurons capable of transmitting the excitement not only the same cells, but also elements of other tissues.
division
Thus, there is a cyclic pattern.The vital processes of cells in it are repeated during the entire period of the interphase and end with either cell death or its division.Self-reproduction is the key to the preservation of life in general, after the disappearance of a particular organism.During cell growth exceeds assimilation dissimilation, the volume is growing faster than the surface.As a result, the processes of cell activity decelerated begin a profound transformation, at the end of which the existence of cells becomes impossible, it goes to the division.Once the formation of new cells with increased capacity and metabolism.
can not say what the life processes of cells play the most important role.They are all interrelated and are meaningless in isolation from each other.Slim and well-oiled mechanism of the existing in the cell, once again recalls the wisdom and grandeur of nature.
