Cell biology is generally known to every school curriculum. We invite you to recall what was once studied, and also to discover something new about it. The name "cell" was proposed back in 1665 by the Englishman R. Hooke. However, it was only in the 19th century that they began to study it systematically. Scientists are interested, among other things, and the role of cells in the body. They can be part of many different organs and organisms (eggs, bacteria, nerves, red blood cells), or they can be independent organisms (protozoa). Despite all their diversity, a lot of similarities are revealed in their functions and structure.
Cell function
All of them are different in form and often in function. Cells of tissues and organs of one organism can differ quite strongly. However, cell biology highlights the functions that are inherent in all their varieties. It is here that protein synthesis always takes place. This process is controlled by the genetic apparatus. A cell that does not synthesize proteins is essentially dead. A living cell is one whose components are constantly changing. However, the main classes of substances remain unchanged.
All processes in the cell are carried out using energy. This is nutrition, respiration, reproduction, metabolism. Therefore, a living cell is characterized by the fact that an energy exchange takes place in it all the time. Each of them has a common most important property - the ability to store energy and spend it. Among other functions, division and irritability can be noted.
All living cells can respond to chemical or physical changes in the environment surrounding them. This property is called excitability or irritability. In cells, upon excitation, the rate of decomposition of substances and biosynthesis, temperature, and oxygen consumption change. In this state, they perform the functions inherent to them.
Cell structure
Its structure is quite complex, although it is considered the simplest form of life in a science such as biology. Cells are located in the intercellular substance. It provides them with breathing, nutrition and mechanical strength. The nucleus and cytoplasm are the main components of each cell. Each of them is covered with a membrane, the building element for which is a molecule. Biology has established that a membrane consists of many molecules. They are located in several layers. Due to the membrane, substances penetrate selectively. In the cytoplasm are organelles - the smallest structures. This is the endoplasmic reticulum, mitochondria, ribosomes, cell center, Golgi complex, lysosomes. You’ll better understand what cells look like by looking at the drawings presented in this article.
Membrane
When examining a plant cell under a microscope (for example, an onion root), you will notice that it is surrounded by a rather thick shell. The squid has a giant axon, the shell of which is of a completely different nature. However, she does not decide which substances should or should not be allowed into the axon. The function of the cell membrane is that it is an additional means of protecting the cell membrane. The membrane is called the "cell wall". However, this is true only in the sense that it protects and protects its contents.
Both the membrane and the internal contents of each cell are usually composed of the same atoms. We are talking about carbon, hydrogen, oxygen and nitrogen. These atoms are at the beginning of the periodic table. The membrane is a molecular sieve, very small (its thickness is 10 thousand times less than the thickness of the hair). Its pores resemble narrow long passages made in the fortress wall of some medieval city. Their width and height are 10 times less than their length. In addition, holes in this sieve are very rare. In some cells, pores occupy only one millionth of the entire membrane area.
Core
Cell biology is also interesting from the point of view of the nucleus. This is the largest organoid, the first to attract the attention of scientists. In 1981, the cell nucleus was discovered by Robert Brown, a Scottish scientist. This organoid is a kind of cybernetic system where storage, processing, and then transmission to the cytoplasm of information takes place, the volume of which is very large. The nucleus is very important in the process of heredity, in which it plays a major role. In addition, it performs the function of regeneration, that is, it is able to restore the integrity of the entire cell body. This organoid regulates all of the most important cell functions. As for the shape of the nucleus, most often it is spherical, as well as ovoid. Chromatin is the most important component of this organoid. This is a substance that is well stained with special nuclear dyes.
A double membrane separates the nucleus from the cytoplasm. This membrane is associated with the Golgi complex and with the endoplasmic reticulum. There are pores on the nuclear membrane through which some substances easily pass, while others are more difficult to do. Thus, its permeability is selective.
Nuclear juice is the internal contents of the kernel. It fills the space between its structures. Be sure to have nucleoli in the nucleus (one or more). They form ribosomes. There is a direct relationship between the size of the nucleoli and the activity of the cell: the nucleoli are larger, the more active is the protein biosynthesis; and, conversely, in cells with limited synthesis, they are either completely absent or small.
There are chromosomes in the nucleus. These are special threadlike formations. In addition to genital, in the nucleus of the cell of the human body there are 46 chromosomes. They recorded information about the hereditary inclinations of the body, which is transmitted to the offspring.
Cells usually have one nucleus, but there are also multinucleated cells (in the muscles, in the liver, etc.). If you remove the nucleus, the remaining parts of the cell will become unviable.
Cytoplasm
The cytoplasm is a colorless mucous semi-liquid mass. It contains about 75-85% of water, about 10-12% of amino acids and proteins, 4-6% of carbohydrates, from 2 to 3% of lipids and fats, as well as 1% of inorganic and some other substances.
The cell contents located in the cytoplasm are able to move. Due to this, the organelles are optimally placed, and biochemical reactions proceed better, as is the process of isolation of metabolic products. Different formations are represented in the cytoplasm layer: superficial outgrowths, flagella, cilia. The retinal system (vacuolar) penetrates the cytoplasm, consisting of flattened sacs, vesicles, tubules communicating with each other. They are associated with the outer plasma membrane.
Endoplasmic reticulum
This organoid was named so because it is located in the central part of the cytoplasm (from the Greek language the word "endon" is translated as "inside"). EPS is a very extensive system of vesicles, tubes, tubules of various shapes and sizes. They are delimited from the cell cytoplasm by membranes.
There are two types of EPS. The first is granular, which consists of tanks and tubules, the surface of which is dotted with granules (grains). The second type of EPS is agranular, that is, smooth. Faces are ribosomes. It is curious that mainly granular EPS is observed in the cells of animal embryos, whereas in adult forms it is usually agranular. As is known, ribosomes are the site of protein synthesis in the cytoplasm. Based on this, it can be assumed that granular EPS occurs mainly in cells where active protein synthesis occurs. The agranular network is believed to be present mainly in those cells where active synthesis of lipids, i.e. fats and various fat-like substances, proceeds.
Both types of EPS do not just take part in the synthesis of organic substances. Here, these substances accumulate and are transported to the necessary places. EPS also regulates the metabolism that occurs between the environment and the cell.
Ribosomes
These are cellular non-membrane organoids. They are composed of protein and ribonucleic acid. These parts of the cell are still not fully understood from the point of view of the internal structure. Under an electron microscope, ribosomes look like mushroom or rounded granules. Each of them is divided into small and large parts (subunits) using a groove. Several ribosomes are often combined by a strand of a special RNA (ribonucleic acid) called i-RNA (informational). Thanks to these organoids, protein molecules are synthesized from amino acids.
Golgi complex
The products of biosynthesis enter the lumens of the tubules and cavities of the EPS. Here they are concentrated in a special apparatus called the Golgi complex (indicated in the figure above as the golgi complex). This unit is near the core. He takes part in the transfer of biosynthesis products that are delivered to the surface of the cell. The Golgi complex is also involved in their elimination from the cell, in the formation of lysosomes, etc.
This organoid was discovered by Camilio Golgi, an Italian cytologist (years of life - 1844-1926). In honor of him in 1898, he was named the Golgi apparatus (complex). Proteins produced in ribosomes enter this organoid. When they are needed by some other organoid, a part of the Golgi apparatus is separated. Thus, the protein is transported to the desired location.
Lysosomes
Talking about how the cells look and what organoids are included in their composition, it is necessary to mention lysosomes as well. They have an oval shape, they are surrounded by a single-layer membrane. In lysosomes there is a set of enzymes that destroy proteins, lipids, carbohydrates. If the lysosomal membrane is damaged, the enzymes break down and destroy the contents inside the cell. As a result of this, she perishes.
Cell center
It is found in cells that are capable of dividing. The cell center consists of two centrioles (rod-shaped bodies). Being near the Golgi complex and the nucleus, it participates in the formation of the spindle of division, in the process of cell division.
Mitochondria
Energy organoids include mitochondria (pictured above) and chloroplasts. Mitochondria are a kind of energy station of each cell. It is in them that energy is extracted from nutrients. Mitochondria have a variable shape, but most often these are granules or threads. Their number and size are variable. It depends on the functional activity of a particular cell.
If we consider an electron micrograph, we can see that mitochondria have two membranes: an inner and an outer one. The inner forms outgrowths (cristae), covered with enzymes. Due to the presence of cristae, the total surface of mitochondria increases. This is important in order for enzyme activity to proceed actively.
In mitochondria, scientists discovered specific ribosomes and DNA. This allows these organoids to multiply independently in the process of cell division.
Chloroplasts
As for chloroplasts, in shape it is a disk or ball having a double shell (inner and outer). Inside this organoid, there are also ribosomes, DNA and grains - special membrane formations associated both with the inner membrane and with each other. Chlorophyll is found in gran membranes. Thanks to it, the energy of sunlight is converted into chemical energy by adenosine triphosphate (ATP). In chloroplasts, it is used for the synthesis of carbohydrates (formed from water and carbon dioxide).
You must admit that the information presented above must be known not only in order to pass a biology test. A cell is the building material that our body is made of. And all wildlife is a complex collection of cells. As you can see, many components stand out in them. At first glance, it might seem that studying the structure of a cell is not an easy task. However, if you look, this topic is not so complicated. It is necessary to know it in order to be well versed in a science such as biology. The composition of the cell is one of its fundamental topics.