The eukaryotic cell It has a membrane that encloses the nucleus separating it from the cytoplasm. The prokaryotic cell It does not have structures with membranes inside, that is, its intracellular content is scattered in the cytoplasm.
All living beings are made up of cells that, depending on their structure, can be eukaryotic or prokaryotic. The French naturalist, zoologist, and biologist Édouard Pierre Léon Chatton (1883-1947) was the first to distinguish between eukaryotic organisms, those with cells with a nucleus, and prokaryotes, which are nucleated.
Prokaryotic cell Eukaryotic cell Definition Cell without a defined nucleus, its genetic material is dispersed in the cytoplasm. Cell with a nucleus defined by a membrane that contains the genetic material. Size Between 1 and 10 microns. Between 10 and 100 microns. Shape It can be spherical, stick, orthographic comma, or spiral. Although they are unicellular, they can form colonies. Very varied, they can constitute unicellular or multicellular organisms. Genetic information Located in a nucleoid, without being surrounded by a membrane. DNA and proteins form the chromatin that is concentrated in the nucleus Direct cell division, mainly by binary fission. There is no mitotic spindle or microtubules. By mitosis and meiosis. It has a mitotic spindle, or some form of microtubule arrangement. Genes Expressed in groups called operons. Individually voiced; They have introns and exons. Ribosomes Present but small (70S) Present and large (80S) Simple flagellum, formed by the flagellin protein. Composite, formed by tubulin and other proteins. Chromosomes Single circular chromosome. multiple. Each with two chromatids, centromere and telomeres. Cell Wall Present Only present in plants and fungi. Domains Bacteria and Archaea The domain Eukarya that groups plants, animals and fungi. Examples The bacterium Staphylococcus aureusthe archa Halobacterium salinarum.
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What is a eukaryotic cell?
the protozoan Blepharisma japonicum It is an example of a eukaryotic cell.
The eukaryotic cell is the building block of life for protozoa, fungi, plants, and animals. It is characterized by keeping its genetic material packaged within a membrane, forming the nucleus. It also has other intracellular structures surrounded by membranes, known as organelles: mitochondria, vesicles, chloroplasts, among others.
The word “eukaryote” comes from the Greek euwhich means “true” and karyon, which means “nut or kernel”. The eukaryotic cell is the basis for the classification of organisms within the domain eukarya.
Characteristics of eukaryotic cells
Assorted shapes: Depending on the environment where the cell is located, it can be spherical, cubic, pyramidal, flat or star-shaped.
Assorted sizes: eukaryotic cells can measure from 10 µm (like lymphocytes) to 100 µm (like adipocytes or adipose cells).
Miscellaneous functions: Although eukaryotic unicellular beings, such as parasites, must perform all the functions necessary for their survival, in multicellular beings there are cells with different functions. For example, the cells of the intestine are designed to absorb nutrients and send them to the blood, from where they are distributed. Plant root cells absorb nutrients and water from the soil.
Presence of organelles: Within the eukaryotic cell are specialized structures for specific functions, including chloroplasts, the Golgi apparatus, mitochondria, vesicles, and lysosomes.
Classification of eukaryotic cells
There are two large groups of eukaryotic cells: the animal cell and the plant cell. A special case is found in fungal cells, which share characteristics of both animal and plant cells.
Animal cell
The animal cell has a plasma membrane, nucleus and cytoplasm. Within the nucleus the genetic material is stored and is composed of the nucleoplasm and the nuclear envelope. Most of the chemical reactions necessary for the proper functioning of the cell take place in the cytoplasm.
Animal cells have a plasma membrane composed of lipids and proteins, which is the barrier that prevents or allows the entry and exit of compounds into the cell. Since the animal cell does not carry out photosynthesis, it does not have chloroplasts. Nor does it have a cell wall, like the plant cell.
Characteristic examples of animal cells are neurons in the nervous system, leukocytes in the immune system, eggs, and sperm in the reproductive system.
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Plant cell
Like the animal cell, it has a differentiated nucleus, membrane, and cytoplasm. However, the plant cell contains chloroplastsstructures that are responsible for the process of photosynthesis.
Thanks to photosynthesis, plants absorb energy from the sun and capture carbon dioxide to synthesize organic compounds and release oxygen into the atmosphere.
In addition, plant cells have a cell wall, an external structure that covers the plasma membrane. The cell wall supports and protects the cell, while allowing intercellular communication.
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fungus cell
Fungal cells are eukaryotic and share common characteristics with animal and plant cells:
They have a cell wall like plant cells, whose chemical composition (chitin) varies depending on the species. They do not perform photosynthesis, so their cells do not have chloroplasts, like the animal cell.
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What is a prokaryotic cell?
The bacteria Escherichia coli It is a cylindrical bacillus that lives in the intestines of animals.
The prokaryotic cell is a simple organism composed of membrane and cytoplasm, which it lacks core and neither does it present organelles like eukaryotic cells (mitochondria, chloroplasts and endoplasmic reticulum). In addition, it has a cell wall that supports the cell.
The word “prokaryote” comes from the Greek prowhich means “before”, and karyon, which means “nut or kernel”. Metabolic reactions in prokaryotic cells are scattered throughout the cytoplasm. They can be autotrophic (such as cyanobacteria) or heterotrophic (such as lactobacilli).
Characteristics of prokaryotic cells
Assorted shapes: Prokaryotic cells can be spherical (as in staphylococci), columnar (as in Escherichia coli), spirals (like the Helicobacter pylori) or curved (like the Vibrio cholerae).
Assorted sizes: Prokaryotic cells are smaller, they can measure from 0.1 µm like mycoplasmas, to 20.0 µm like the Treponema pallidum, causative agent of syphilis.
Presence of cell wall: the cell membrane is surrounded by the cell wall composed of peptidoglycan, a characteristic polymer of bacteria.
Capsule presence: Some bacteria have a mucous layer on the outside, known as a capsule.
Classification of prokaryotic cells
Biologically, they can be classified into two main groups: archaea and bacteria.
archaea
The archaea belong to the domain Archaea. These cells are microscopic and are wrapped in a cell wall, composed of a pseudopeptidoglycan, which protects them and gives them greater resistance. They are found in marine and terrestrial environments, being able to survive under extreme environmental conditions where other living things do not survive. For this reason they are given the adjective of extremophiles.
Examples of archaea are the Methanothermus ferviduswho lives in the hot springs (97ºC) and the Methanobacterium thermoaggreganswhich produces methane and lives at 65ºC.
bacteria
Bacteria belong to the domain Bacterium. Its cell wall is composed of peptidoglycans and presents ester lipids. Unlike archaea, bacteria can produce spores and some photosynthesize.
Examples of bacteria are Helicobacter pylorithe causative agent of gastric ulcers, and yogurt-producing bacteria, Lactobacillus bulgaricus and Streptococcus thermophiles.
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