Eukaryotic cell and prokaryotic cell

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 nuclei, and prokaryotes, which are enucleated..

	Prokaryotic cell	Eukaryotic cell
Definition	Cell without a defined nucleus, its genetic material is scattered 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, rod-shaped, 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
Cellular division	Direct, mainly by binary fission. No mitotic spindle or microtubules.	By mitosis and meiosis. Has mitotic spindle, or some form of microtubule arrangement.
Genes	Expressed in groups called operons.	Individually expressed; possess introns and exons.
Ribosomes	Present but small (70S)	Present and great (80S)
Flagellum	Simple, formed by the flagellin protein.	Composite, consisting of tubulin and other proteins.
Chromosomes	Single circular chromosome.	Multiple. Each with two chromatids, centromere and telomeres.
Cellular wall	Present	Only present in plants and fungi.
Domains	Bacteria and Archaea	The Eukarya domain that groups plants, animals and fungi.
Examples	The bacteria Staphylococcus aureus, the arches Halobacterium salinarum.	Yeast in bread Saccharomyces cerevisiae, the fruit fly Drosophila melanogaster, the banana or 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 domain Eukarya.

Characteristics of eukaryotic cells

• Varied forms: depending on the environment where the cell is located, it can be spherical, cubic, pyramidal, flat or stellate.
• Assorted sizes: eukaryotic cells can measure from 10 µm (like lymphocytes) to 100 µm (like adipocytes or fat cells).
• Various functions: Although eukaryotic unicellular beings, like parasites, must perform all the necessary functions for their survival, in multicellular beings there are cells with different functions. For example, cells in the intestine are designed to absorb nutrients and deliver 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 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 carry out photosynthesis, 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

The cells of fungi 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, which it lacks core and it also does not 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 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 forms: prokaryotic cells can be spherical (as in staphylococci), cylindrical (as the Escherichia coli), spirals (like the Helicobacter pylori) or curved (such as 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.
• Cell wall presence: 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 domain Archaea. 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 things do not survive. For this reason they are given the adjective of extremophiles.

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

Bacteria

Bacteria belong to the domain Bacterium. 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, causative agent of gastric ulcers, and yogurt-producing bacteria, Lactobacillus bulgaricus Y Streptococcus thermophiles.

You may also like:

• Archeas and bacteria
• Autotrophic and heterotrophic organisms

See also:

• Animal and plant cell
• Cell types