All living organisms, depending on the presence of the nucleus, can be divided into two large categories: prokaryotes and eukaryotes. Both of these terms originate from the Greek "karion" - the core.
Those organisms that do not have a nucleus are called prokaryotes - pre-nuclear organisms with nuclear matter in the form of inclusions. The structure of the eukaryotic cell is somewhat different. Unlike prokaryotes, eukaryotes have a shaped core - this is their main difference. Prokaryotes include bacteria, cyanobacteria, rickettsia and other organisms. Representatives of the kingdoms Mushrooms, Plants and Animals can be attributed to eukaryotes.
The structure of eukaryotic cells of various nuclear organisms is similar. Their main components are the nucleus and cytoplasm, which together make up the protoplast. The cytoplasm is a semi-liquid basic substance, or, as it is also called, the hyaloplasm, in which there are cellular structures - organelles that perform various functions. On the outside, the cytoplasm is surrounded by a plasma membrane. In addition to the plasma membrane, plant and fungal cells have a rigid cell membrane. The cytoplasm of plant and fungal cells contains vacuoles - vesicles that are filled with water with various substances dissolved in it. In addition, there are inclusions in the cell in the form of reserve nutrients or end products of metabolism. The structural features of the eukaryotic cell are due to the functions of inclusions in the cell.
The structure and functions of the eukaryotic cell :
- the plasma membrane is a double lipid layer with proteins immersed in it. The main function of the plasma membrane is the metabolism between the cell itself and the environment. Due to the plasma membrane, contact is also made between two neighboring cells.
- nucleus - this cellular element has a two-membrane membrane. The main function of the nucleus is the preservation of hereditary information - deoxyribonucleic acid. Thanks to the nucleus, cellular activity is regulated, and genetic material is transmitted to daughter cells.
- mitochondria - these organelles are present only in plant and animal cells. Mitochondria, like the nucleus, have two membranes between which there are internal folds - cristae. Mitochondria contain circular DNA, ribosomes, and many enzymes. Thanks to these organelles, the oxygen phase of the cell respiration is carried out (adenosine triphosphoric acid is synthesized).
- Plastids are found only in the plant cell, since their main function is the implementation of photosynthesis.
- the endoplasmic reticulum (reticulum) is a whole system of flattened sacs - cisterns, cavities and tubules. On the endoplasmic reticulum (rough) are important organelles - ribosomes. In the tanks of the network, proteins are isolated and mature, which are also transported by the network itself. On the membranes of the smooth reticulum, the synthesis of steroids and lipids is carried out.
- Golgi complex - a system of flat single-membrane tanks and bubbles attached to the extended ends of the tanks. The function of the Golgi complex is the accumulation and transformation of proteins and lipids. Here, secretory vesicles are formed, leading substances outside the cell. The structure of the eukaryotic cell is such that the cell has its own mechanism for the allocation of waste substances.
- lysosomes are single-membrane vesicles that contain hydrolytic enzymes. Thanks to the lysosomes, the cell digests damaged organelles, dead organ cells.
- ribosomes are of two types, but their main function is the assembly of protein molecules.
- centrioles are a system of microtubules that are built from protein molecules. Thanks to centrioles, the inner skeleton of the cell is formed, it can maintain its constant shape.
The structure of a eukaryotic cell is more complex than prokaryotic cells. Due to the presence of the nucleus, eukaryotes are able to transmit genetic information, thereby ensuring the constancy of their species.