Animal cell Concept, Parts and Differences with the Vegetal
What is an animal cell?
We explain what an animal cell is and the theories of its possible origin. In addition, its parts and the differences with the plant cell.
The animal cell is adapted to the biochemical functions of the animal organism.
An animal cell is a type of eukaryotic cell (i.e. endowed with a true nucleus) presented by the various tissues of living beings belonging to the Animalia kingdom.
These cells are adapted to the biochemical functions of the animal organism, such as its metabolism and forms of nutrition (respiration, heterotrophic nutrition).
Since animals are all complex multicellular beings, their cells have a very high level of specialization, that is, depending on the tissue to which they belong, they perform specific functions that define their form, their way of operating and their needs. A human being, for example, has about 200 million different cell types.
The emergence of the animal kingdom, unlike the vegetable kingdom, starts from a question: it is not known for certain how the transit between protozoa and metazoa occurred, that is, between unicellular life and specialized multicellular organization, since there is no evidence of it in the fossil record. But there are three theories about it:
- Colonial origin. The complex animal life would have arisen from colonies of cells inhabiting in a joint way, that when adapting to the necessities of survival, were specializing more and more in some defensive or logistic aspect indispensable for the colony: movement, defense, organization, etc.
- Symbiotic origin. This theory supposes that pluricellular life would come from a complex case of symbiosis, in which many cells began to cohabit in a positive way for all, helping each other and taking care of each other to such a degree that little by little more and more were needed until they began to operate as a single individual.
- Origin by cellularization. It is based on the idea that pluricellular animals would be the consequence of the cellularization processes of the cell nuclei of a primitive organism, whose cells had more than one nucleus. Thus, by generating compartments to protect them, it would have been forming cells within the cell and growing in internal level of complexity.
Parts of an animal cell
The nucleus is wrapped in a nuclear membrane and surrounded by nucleoplasm.
The usual parts of an animal cell are:
- Core. Like all eukaryotes, animals have cells with a well-defined nucleus in which all their genetic material is housed and which plays key roles in cell reproduction. The nucleus is wrapped in a nuclear membrane and surrounded by nucleoplasm, which allows exchange with the cytoplasm.
- Plasma membrane. The selective membrane that covers the cell and distinguishes its inside from its outside, allowing the entry of desired substances and the exit of metabolic waste.
- Cytoplasm. The interior of the cell, where the nucleus and the cellular organelles are located, is a very fine, granular colloidal substance, in which many metabolic processes have their place.
- Mitochondria. The energy plants of the cell, responsible for the synthesis of ATP (chemical energy molecule) from cellular nutrients. This is known as cellular respiration.
- Lysosomes. In charge of degrading the material that enters the cell (heterophagia) or is produced within it (autophagia), these organelles in charge of cellular digestion are created by the golgi apparatus.
- Golgi apparatus. Common in animal and plant cells, this is a series of membranes within the cell, which serve as a transport channel for proteins and other substances through a system of vesicles in and out of the cytoplasm.
- Endoplasmatic reticulum. A series of interconnected flattened tubules and sacs composed of fatty acids. It is divided into two domains with different functions: the rugged endoplasmic reticulum, covered with ribosomes in which protein synthesis takes place; and the smooth endoplasmic reticulum, vital in lipid synthesis, as well as in the absorption and release of calcium from the cell.
- Centriolo. A cylindrical organelle made up of three microtubule triplets, part of the cytoskeleton (cellular framework), and located in the cytoplasm, in a region called the diplosome. These ducts have an important role in the transport of organelles in the cell and also in the processes of mitosis or cell division.
- Chromatin. This is the name given to the set of DNA, histone and non- histone proteins that is found in the cell nucleus and composes the genetic material of the cell. Its basic units of information are nucleosomes.
Differences between animal cell and plant cell
Vegetable and fungal cells have a rigid cell wall.
The differences between animal and plant cells can be summarized as follows:
- Cell wall. Vegetable and fungal cells have a rigid cell wall, which limits their growth but makes them more compact. This wall is outside the plasma membrane and is composed of cellulose (vegetables) or chitin (fungi). It does not occur in animal cells.
- Size Animal cells are smaller than plant cells, perhaps because they do not have a central vacuole filled with liquid, but small and numerous vacuoles in their cytoplasm.
Chloroplasts. Since plants make photosynthesis, their cells have chloroplasts: organelles in which chlorophyll, indispensable for obtaining energy from sunlight, is housed.
Animal cells therefore lack such organelles and have in place what is necessary for glucose oxidation (respiration).