Cell structure of various organisms
The cell is the main structural and functional unit of all living organisms, except viruses. It has a specific structure, including many components that perform certain functions.
What science is studying the cell?
Everyone knows that the science of living organisms is biology. The structure of the cell studies its branch - cytology.
What does a cell consist of?
This structure consists of a membrane, cytoplasm, organoids, or organelles, and the nucleus (absent in prokaryotic cells). The structure of cells of organisms belonging to different classes varies slightly. Significant differences are observed between the structure of the cells of eukaryotes and prokaryotes.
The membrane plays a very important role - it separates and protects the contents of the cell from the external environment. It consists of three layers: two protein and medium phospholipid.
Another structure that protects the cell from external factors is located on top of the plasma membrane.Present in the cells of plants, bacteria and fungi. In the former, it consists of cellulose, in the latter - from murein, in the third - from chitin. In animal cells on top of the membrane is glycocalyx, which consists of glycoproteins and polysaccharides.
It represents the entire cell space bounded by the membrane, with the exception of the nucleus. Cytoplasm includes organelles that perform the basic functions responsible for the vital activity of the cell.
Organelles and their functions
The cell structure of a living organism implies a number of structures, each of which performs a specific function. They are called organelles, or organoids.
They can be called one of the most important organelles. Mitochondria are responsible for the synthesis of energy necessary for life. In addition, they are involved in the synthesis of certain hormones and amino acids.Energy in the mitochondria is produced due to the oxidation of ATP molecules, which occurs with the help of a special enzyme called ATP synthase. Mitochondria are round or rod-shaped structures. Their number in an animal cell, on average, is 150-1500 units (it depends on its purpose).They consist of two membranes and a matrix - a semi-liquid mass that fills the inner space of an organelle. The main component of the membranes are proteins, and phospholipids are also present in their structure. The space between the membranes is filled with liquid. In the mitochondrial matrix there are grains that accumulate certain substances, such as magnesium and calcium ions, necessary for energy production, and polysaccharides. Also, these organelles have their own protein biosynthesis apparatus, similar to that of prokaryotes. It consists of mitochondrial DNA, a set of enzymes, ribosomes and RNA. The structure of the cell of prokaryotes has its own characteristics: there are no mitochondria in it.
These organelles are composed of ribosomal RNA (rRNA) and proteins. Thanks to them, translation is carried out - the process of protein synthesis on an mRNA matrix (messenger RNA). Up to ten thousand given organoids can be contained in one cell. Ribosomes consist of two parts: small and large, which are combined directly in the presence of mRNA.The ribosomes that are involved in the synthesis of proteins essential for the cell itself are concentrated in the cytoplasm.And those with which proteins are produced that are transported outside the cell are located on the plasma membrane.
It is present only in eukaryotic cells. This organella consists of dictosomes, the number of which is usually about 20, but can reach up to several hundred. The Golgi apparatus enters the cell structure of only eukaryotic organisms. It is located near the nucleus and performs the function of synthesis and storage of certain substances, for example, polysaccharides. It forms lysosomes, which will be discussed below. Also this organella is part of the excretory system of the cell. Dictosomes are presented in the form of stacks of flattened disc-shaped cisterns. At the edges of these structures, bubbles form where there are substances that need to be removed from the cell.
These organelles are small vesicles with a set of enzymes. Their structure has one membrane, covered on top with a layer of protein. The function that lysosomes perform is intracellular digestion of substances. Due to the enzyme hydrolase, the above-mentioned organelles break down fats, proteins, carbohydrates, nucleic acids.
Endoplasmic reticulum (reticulum)
The cell structure of all eukaryotic cells implies the presence of EPS (endoplasmic reticulum). The endoplasmic reticulum consists of tubes and flattened cavities that have a membrane. This organoid is of two types: a rough and smooth network. The first is distinguished by the fact that ribosomes are attached to its membrane, the second has no such feature. A rough endoplasmic reticulum performs the function of the synthesis of proteins and lipids, which are required for the formation of the cell membrane or for other purposes. Smooth takes part in the production of fats, carbohydrates, hormones and other substances, except proteins. Also, the endoplasmic reticulum performs the function of transporting substances around the cell.
It consists of microtubules and microfilaments (actin and intermediate). The components of the cytoskeleton are polymers of proteins, mainly actin, tubulin or keratin. Microtubules serve to maintain the shape of the cell, they form organs of movement in protozoa, such as ciliates, chlamydomonads, eugleins, etc. Actin microfilaments also play the role of a framework.In addition, they are involved in the process of moving organelles. Intermediates in different cells are made up of various proteins. They maintain the shape of the cell, and also fix the nucleus and other organelles in a constant position.
Consists of centrioles, which have the shape of a hollow cylinder. Its walls are formed from microtubules. This structure is involved in the process of division, ensuring the distribution of chromosomes between daughter cells.
In eukaryotic cells, it is one of the most important organoids. It stores DNA, which encrypts information about the entire body, its properties, proteins that must be synthesized by the cell, etc. It consists of a shell that protects the genetic material, nuclear juice (matrix), chromatin and the nucleolus. The shell is formed of two porous membranes located at some distance from each other. The matrix is represented by proteins, it forms inside the nucleus a favorable environment for the storage of hereditary information. The nuclear juice contains filamentous proteins that serve as a support, as well as RNA. Also present here is chromatin - the interphase form of the existence of chromosomes.During cell division from the clumps, it turns into rod-shaped structures.
This is a separate part of the nucleus responsible for the formation of ribosomal RNA.
Organelles inherent only to plant cells
Plant cells have some organoids that are not peculiar to any organisms. These include vacuoles and plastids.
This is a kind of reservoir where spare nutrient materials are stored, as well as waste products, which cannot be brought out due to the dense cell wall. It is separated from the cytoplasm by a specific membrane called a tonoplast. As the cell functions, separate small vacuoles merge into one large - central one.
These organelles are divided into three groups: chloroplasts, leukoplasts and chromoplasts.
These are the most important organoids of the plant cell. Thanks to them, photosynthesis is performed, during which the cell receives the nutrients it needs. Chloroplasts have two membranes: external and internal; matrix - a substance that filled the inner space; own DNA and ribosomes; starch grains; grana. The latter consist of stacks of thylakoids with chlorophyll, surrounded by a membrane.It is in them and the process of photosynthesis.
These structures consist of two membranes, matrix, DNA, ribosomes and thylakoids, but the latter do not contain chlorophyll. Leukoplasts perform a spare function, accumulating nutrients. They contain special enzymes that allow you to get starch from glucose, which, in fact, serves as a spare substance.
These organoids have the same structure as those described above, but they do not contain thylakoids, but there are carotenoids that have a specific color and are located directly near the membrane. It is thanks to these structures that the petals of flowers are colored in a certain color, allowing them to attract insect pollinators.