When we see around ourselves uh, we find uh that there is a presence of the basic unit of light that is called as the cell. In all the living organisms, all organisms they are composed of cells. Some are composed of single cells. They are unicellular, while others like us, they are composed of many cells, which are called as multicellular now in this chapter well be covering all these topics. What is the cell cell theory and overview of a cell uh prokaryotic cell cell envelope and its modifications, ribosomes and inclusion bodies, eukaryotic cells, cell membrane cell wall, endo membrane systems, including endoplasmic reticulum, golgi apparatus, lysosomes, vacuoles, nucleus, microbodies, mitochondria, plastids, ribosome, celia, flagella, centrosome and centrioles? Now, what is the cell now unicellular organisms? They are capable of independent existence and they perform all the essential functions of life. Anything less than a complete structure of a cell does not ensure independent living. Hence cell is the fundamental structural and functional unit of all living organisms anthony when leuven hook first saw and described a live cell. Robert brown later discovered the nucleus and the invention of the microscope, and its importance leading to the electron microscope revealed all the structural details of the cell cell theory. In 1838, matthias schledin, a german botanist, examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant. At about the same time, clearer schwann.
In 18′, a british zoologist studied different type of animal cells and reported that cells had a thin outer layer which is today known as a plasma membrane. He also concluded, based on his studies on plant tissues, that the presence of a cell wall is a unique character of the plant cells on the basis of this, schwann proposed the hypothesis that the bodies of animals and plants are composed of cells and products of cells. Schlitten and schwann together formulated the cell theory, and this theory did not explain as to how new cells are formed. Rudolph were shown in 1855. He first explained that cells, divide and new cells are formed from the pre existing cells ominous cellulase cellular uh. He modified the hypothesis of schliedern schwann to give the cell theory a final shape. Cell theory is now understood, as all living organisms are composed of cells and products of cells and all cells arise from pre existing cells, an overview of a cell. We have observed that cell in the onion peel human cheek cells in a microscope. Now the onion cells, which is typically a plant cell, has a distinct cell wall and its outer boundary and within its a membrane, the cells of the human cheeks. They do. They have an outer membrane and a structure delimiting structure inside the cell, so inside each cell is a dense membrane. Bound structure called nucleus nucleus in each cell is present, and this nucleus contains the chromosomes which in turns, contain the genetic material which is called as the dna cells that have membrane bound nuclei.
They are called eukaryotes, whereas which lack a membrane and the nucleus proper nucleus. They are prokaryotes, so in both prokaryotes and eukaryotes are semi fluid matrix, which is called as cytoplasm cytoplasm is present. It occupies the volume of the cell and is the main area for the cellular activities in both plants and animals. So, besides the nucleus, there are various organelles like endoplasmic reticulum, golga operators, lysosomes, etc. They are there in the cells. Cells differ greatly in size, shape and activities. For example, microplasmas microplasmas. They are the smallest cell, with 0.3 micrometers in length, while bacteria, whereas bacteria they are three to five micrometers and the largest isolated single cell is of the cell of an ostrich and human red blood cells. They are about human red blood cells, theyre about 7 micrometers. In diameter, nerve cells are some of the longest cells and nerve cells. These are the longest cells and they also vary greatly in their shape. They may be disk like polygonal columnar cuboid thread like or even irregular, so the shape of the cell may vary with the functions they perform cell. The prokaryotic cells are represented by bacteria, blue, green algae, microplasmas and pplo. That is plural pneumonia, like organism they are generally smaller and multiply more rapidly than the eukaryotic cells. They may vary greatly in shape and size, and the four basic shapes of bacteria are bacillus. Rod like coca spherical, vibrio, common shaped and spirulum. That is spiral.
So the organization of the prokaryotes is fundamentally similar, even though prokaryotes exhibit a wide variety of shapes and functions. All prokaryotes have a cell wall surrounding the cell membrane. They have a cell wall and the fluid matrix fluid inside, which is called as the cytoplasm and the genetic material is basically naked and is not employed by a nuclear membrane. In addition of the genome dna, the single chromosome or circular dna and bacteria may have small circular dna outside the genomic dna, and these smaller dnas are called as plasmids. You can see here in the diagram plasmid, so dna is used to monitor the bacterial transformation with foreign dna and nuclear membrane is found in eukaryotes and it is found in prokaryotic cells, except for ribosomes, so prokaryotes. They have something unique in them in the form of inclusions. A specialized, differentiated form of cell membrane called mesozoic is the characteristic of prokaryotes, and they are essentially in foldings of the cell membrane. Here you can see a typical eukaryotic cell, which is a bigger in size. 10 to 20 micrometers, whereas a typical bacteria measures, one to two micrometers and plural pneumonia like organisms, they are 0.1 micrometer and viruses are 0.02 to 0.2 micrometers cell envelope and its modifications most prokaryotic, particularly the bacterial cells. They have a very complex cell envelope. Cell envelope consists of tightly bonded three layered structure. The outermost is called as glycocalyx, which is formed by the cell wall and the, and then the plasma membrane and each layer of the envelope performs distinct functions, which acts together as a single protective layer.
Bacteria may be classified into two groups on the basis of the differences in the cell envelope. These can be gram, positive and gram, negative bacteria, so it depends on their respond to the staining procedure developed by the gram and those which take up the gram strain. They are called as gram positive and those which do not. They are called as gram. Negative glycogens differ in composition and thickness. When did in different bacteria. When there is a loose, sheath or slime layer, then it is called as while in others it is maybe thick or tough and is called as a capsule like here you can see here. There is a capsule in the case of bacteria, and the cell wall determines the shape of the cell and it provides a strong structural support to prevent the bacteria from bursting or collapsing. The plasma membrane is a semi permeable and interacts with the outer world, and this membrane is similar structurally to that of the eukaryotes. A typical membranous structure is the mesosome which is formed by the extension of the plasma membrane into the cell, and they help in cell wall formation and dna replication and distribution of daughter cells. They also help in respiration secretion process to increase the surface area of the plasma membrane. Bacterial cells may be motile or non motile, and if motile, they have a thin filamentous extension from their cell wall and that is called as a flagellum. Flagellum has a filament hook and a basal body, and the filament is the longer part that extends from the cell surface to the outside.
Besides flagella pili and fimbriae, you can see here. These are pili and another type of structures called fimbre. These are small bristle, like fibers, which are sprouting out of the cells and in some bacteria they are known to help to attach the bacteria to the rocks and stream and also to the host tissues. Here you can see the structure of a flagellum. It has got a structure which is called as filament tip and the junction with which it is attached to the cell wall ribosomes in prokaryotes. These are the prokaryotic ribosomes in prokaryotes. Ribosomes are associated with the plasma membrane of the cell and they are about 15 nanometer by 20 nanometers and they are made up of two subunits, which are called as the 50 and the 30s subunits, which present together as 70s 70s, a prokaryotic ribosome. So ribosomes are the sites of protein synthesis and several ribosomes may attach to a single messenger rna and form a chain which is called as polyribosome or polysome. So the ribosomes of a pro of a polysome. They translate the messenger rna into proteins. Inclusion bodies reserve material in prokaryotes cells. They are stored in the cytoplasm in the form of inclusion bodies. They are not bound by any membrane system. They are free in the cytoplasm like phosphate granules, cyanophysean, granules and glycogen granules gas vacuoles. They are found in the blue, green and purple and the green photosynthetic bacteria. So these inclusion bodies we have just discussed they are lying in the cytoplasm which are can be in the form of phosphate granules, cyanophysean, granules and glycogen granules gas vacuoles.