Eukaryotic cell and prokaryotic cell

The eukaryotic cell has a membrane that encloses the nucleus separating it from the cytoplasm. The prokaryotic cell 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 enucleated.

Prokaryotic cellEukaryotic cell
DefinitionCell without a defined nucleus, its genetic material is scattered in the cytoplasm.Cell with a nucleus defined by a membrane that contains genetic material.
SizeBetween 1 and 10 microns.Between 10 and 100 microns.
ShapeIt can be spherical, rod-shaped, orthographic comma, or spiral. Although they are single-celled, they can form colonies.Very varied, they can constitute unicellular or multicellular organisms.
Genetic informationLocated in a nucleoid, without being surrounded by a membrane.DNA and proteins form the chromatin that is concentrated in the nucleus
Cellular divisionDirect, 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.
GenesExpressed in groups called operons.Individually expressed; they have introns and exons.
RibosomesPresent but small (70S)Present and great (80S)
FlagellumSimple, formed by the flagellin protein.Composite, made up of tubulin and other proteins.
ChromosomesSingle circular chromosome.Multiple. Each with two chromatids, centromere and telomeres.
Cellular wallHere I’mOnly present in plants and fungi.
DomainsBacteria and ArchaeaThe Eukarya domain that groups plants, animals and fungi.
ExamplesThe bacteria Staphylococcus aureus and the Halobacterium salinarumThe bread yeast Saccharomyces cerevisiae, the fruit fly Drosophila melanogaster , the banana Musa sp .

What is 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 packed 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 eu , which means “true” and karyon , which means “nut or kernel.” The eukaryotic cell is the basis for the classification of organisms within the Eukarya domain .

Characteristics of eukaryotic cells

  • Varied shapes: depending on the environment where the cell is located, it can be spherical, cubic, pyramidal, flat or starry.
  • Varied sizes: eukaryotic cells can measure from 10 µm (like lymphocytes) to 100 µm (like adipocytes or fat cells).
  • Varied functions: although eukaryotic unicellular beings, like 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 structures specialized in specific functions, which include 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 achieved in the cells of fungi, which share characteristics of both animal and plant cells.

Animal cell

The animal cell has a plasma membrane, nucleus and cytoplasm. Genetic material is stored within the nucleus 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 photosynthesize, it does not have chloroplasts. It also does not 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.

plant cell

Like the animal cell, it has a differentiated nucleus, membrane, and cytoplasm. However, the plant cell contains chloroplasts , structures that are responsible for the photosynthesis process.

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.

Fungal 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 photosynthesize, so their cells do not have chloroplasts, like the animal cell.

See also Mitosis and meiosis .

What is a prokaryotic cell?

The prokaryotic cell is a simple organism composed of membrane and cytoplasm, lacking a nucleus and also lacking 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 pro , which means “before”, and karyon , which means “nut or kernel.” Metabolic reactions in prokaryotic cells are scattered throughout the cytoplasm. They can be autotrophic (like cyanobacteria) or heterotrophic (like lactobacilli).

Characteristics of prokaryotic cells

  • Varied shapes: prokaryotic cells can be spherical (as in staphylococci), cylindrical (such as Escherichia coli ), spiral (such as Helicobacter pylori ), or curved (such as Vibrio cholerae ).
  • Varied sizes: prokaryotic cells are smaller, they can measure from 0.1 µm like mycoplasmas, to 20.0 µm like Treponema pallidum, the 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.
  • Presence of capsule: 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.

Arches

The archaea belong to the Archaea domain These cells are microscopic and are surrounded by 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 beings do not survive. For this reason they are given the adjective extremophiles.

Examples of archaea are Methanothermus fervidus , which lives in hot springs (97ºC) and Methanobacterium thermoaggregans , which produces methane and lives at 65ºC.

Bacteria

Bacteria belong to the Bacteria domain . Its cell wall is composed of peptidoglycans and has ester-type lipids. Unlike archaea, bacteria can produce spores and some photosynthesize.

Examples of bacteria are Helicobacter pylori , the causative agent of gastric ulcers, and the yogurt-producing bacteria, Lactobacillus bulgaricus and Streptococcus thermophiles.

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