The differentiation of cells and tissues plays a large role in the development of the body. The division of responsibilities for each cell can be compared with the division of labor in the factory: if each unit performs only its inherent function, the overall result can be obtained in a shorter time. The same applies to any living organism whose quality of life depends on its complexity of development and the occupied evolutionary niche.
What is a cell: biology of the body
A cell is a structural and functional unit of all living things. The only exception is viruses - a non-cellular form of life. Tissue is a combination of cells and intercellular substance having the same structure, function and origin. The biology of the function of the cell is based on its structure, which is dictated by the degree of organization of the animal or plant.
The differentiation of cells in animals and plants occurs in ontogenesis. Each of them comes from the precursor tissue: if in animals it is stem cells, then in plants it is a meristem.
What is a cell? The biology and structure of cells allows us to classify them into two groups.
1. Eukaryotic cells. These include the structural units of the animal and plant organism.
2. Prokaryotic cells. They are distinguished by the absence of a nucleus and other organelles. Prokaryotic organisms include bacteria.
The structure of the animal cell
The study of the structure of cells involved in biology. The structure of the animal cell was discovered by Hooke in the 19th century, however, it was fully studied closer to the 20th millennium.
An animal cell is a cytoplasm surrounded by a plasmalemma. Various organelles and inclusions “float” in the cytoplasm. Organelles include lysosomes, mitochondria, Golgi apparatus, endoplasmic reticulum, peroxisomes. Inclusions are substances that are dissolved in the cytosol and wait until they are needed to build cell structures.
Unlike a plant cell, there is no cell wall, vacuole and chloroplasts in the animal cell. The absence of an additional integumentary complex affects, for example, the peculiarities of deformation of the plasmalemma during fission.
Plant cell structure
The inner contents of the plant cell are much richer than the animal. First, here you can find two-membrane structures - chloroplasts. And the function is to provide the process of photosynthesis, which is very important for plants in terms of an additional energy source along with respiration, as well as glucose.
The plant cell is additionally covered with a cell wall. It consists of cellulose fibers, and pectin is still present at the contact site of two neighboring cells. Here, such a powerful external complex does not allow contact in the way that animal cells do. The main role in transport is played by the structure of the cell. Grade 6, in which biology has not yet been studied so deeply, does not provide information about desmosomes - special pores in the cell wall that serve to move substances from one cell to another. Using these structures, vacuoles can be contacted through a small diameter bridge.
Vacuole is another difference between an animal cell and a plant cell. Its function is to store chemically active alkaloids, acids, calcium, which help stabilize the osmotic pressure. Moreover, alkaloids and acids can adversely affect the contents of the cytoplasm, so they must be in an isolated organelle with a special membrane through which molecules of this size cannot penetrate. A vacuole membrane is called a tonoplast.
All structural features of the columnar cell tissue are identical to the above plan of the composition of plant cells.
Prokaryotic cells
Bacteria (as representatives of prokaryotes) are evolutionarily less developed organisms. A bacterial cell is a cytosol surrounded by a membrane, cell wall and mucous capsule. Inside, there are no organelles that are found in eukaryotes. The nucleus is also absent, and all genetic material in most bacteria is represented by only one chromosome.
Cell metabolism is supported by special structures - mesosomes. They represent an outgrowth of the cytoplasmic membrane inside the cell, and their function is respiration or photosynthesis, if we are talking about photosynthetic bacteria.
The absence of a nucleus helps increase the speed of transcription and translation. The rate of binary cell division also increases: a bacterial colony can double its number every 20 minutes.
Cell function
A cell, as a structural and functional unit of all living things, can perform various functions related to the maintenance of vital functions of an organism. The main role here is played by the structure of the cell. Grade 6, in which biology was still studied at the initial level, dictates to us the main features of the organization of the cellular apparatus.
Determination of plant cells is a multi-stage process, as a result of which many other body tissues are formed from the meristem: integumentary, excretory, conductive, mechanical. The cells of each of these tissues differ from each other in structure and function. For example, the task of integumentary cells is not to let foreign agents pass into the body when the conductive elements are needed for the transport of organic and mineral substances through the plant.
The interaction of cells is achieved by special contacts, which are called plasmodesmata. Regulation of work occurs at the biochemical level with the help of various enzymes and metabolites.
Leaf - a vegetative organ of plants
The function of the autonomic organs is to maintain the plant's vital activity at an optimal level. The leaf also belongs to this group, therefore its main task is photosynthesis.
Columnar tissue is the main photosynthetic tissue of the leaf. It consists of parenchymal cells, in which there are many chloroplasts. The cells of the columnar tissue are closer to the upper surface of the leaf in order to receive more solar energy and, accordingly, increase the speed and productivity of photosynthesis.
Also, the composition of the sheet includes spongy tissue, which also has chloroplasts, but their number is much smaller compared to the polysadic parenchyma. The fact is that the main function of the cells of the spongy tissue is gas exchange due to the large intercellular spaces.
Structural Features of the Leaf Cell Column Cell
The palisade parenchyma is located in the upper layers of the leaf to accumulate more solar energy. This is necessary for the effective occurrence of the light and dark stages of photosynthesis, which take place only in the condition of lighting.
A columnar cell is an elongated cell of a cylindrical shape, the main function of which is the process of photosynthesis. For this, several tens of chloroplasts are located in the cells of columnar tissue, which are located on the periphery of the cell. This arrangement in the space of the cytosol is explained by an increase in the absorption surface of sunlight.
In C4 plants of tropical and equatorial forests, the structure of the leaf is slightly different. They have columnar tissue located in the uppermost and lowermost layers of the organ. This is due to the features of the dark stage of photosynthesis in these plants.
The structural features of the columnar tissue cells are used by the plant to increase the efficiency of photosynthesis.
What is photosynthesis?
Photosynthesis is a multi-stage biochemical process in which energy is generated in the form of ATP and glucose - a carbohydrate that is stored by the plant.
Photosynthesis is divided into two stages: light and dark. During the first stage, the photolysis of water, the release of oxygen as a by-substance and the synthesis of ATP, NADPH. The dark stage of photosynthesis is a cascade of sequential reactions that synthesize glucose or sugar analogues.
Why do plants need photosynthesis?
To maintain normal functioning, the plant stores a large amount of starch. Starch is a polysaccharide whose monomer is glucose. Not surprisingly, in the body of a plant, of all possible classes of organic substances, carbohydrates occupy the largest percentage.
The structural features of the columnar cell tissue allow you to effectively absorb light energy, which is necessary for the flow of biochemical photosynthesis reactions. During the dark stage, glucose and other hexoses are synthesized, which are stored in the form of large polymer starch molecules in parenchymal cells. Even in chloroplasts themselves, starch grains can sometimes be observed.