The human body is made up of between 10 and 100 billion cells, which perform different functions, such as providing structure to the body, absorbing nutrients and converting them into energy, among others. All cells can be classified between eukaryotes and prokaryotes.
In this article, we explain in detail what a cell is, what its characteristics, types, parts and functions are .
What is a cell
The cell is the basic biological, functional and structural unit of any living being and, at the same time, the cell is the smallest organism of all, capable of performing the functions of nutrition, relationship and reproduction.
Every living thing is made up of cells . Absolutely all organisms, the tissues that compose them and the internal organs that form them. The skin, hair, eyes, lungs, liver and everything else.
A living being is made up of one, millions or billions of cells distributed to the last recess of its structure. Obviously, not all cells are the same, since many are specialized in some function and are grouped in particular areas. Regardless of whether they are part of a multicellular organism or not, each individual cell is a wonder because it can take nutrients and convert them into energy, have specialized functions and reproduce.
Characteristics and functions of the cell
Additionally, there are other functions that cells perform, among which can be named: containing hereditary material and transmitting it to subsequent generations, absorbing nutrients from food, carrying out vital processes and providing a body structure.
Although they cannot be observed with the naked eye, scientists initially identified them through optical microscopes and, starting in the last century, through electron microscopes. They can have spherical, polyhedral, elongated and prismatic shapes, but the variety of shapes is only present in those living beings made up of more than one cell. In this sense, organisms can be classified as :
- When they are made up of a single cell such as Archaea, bacteria, unicellular algae, unicellular fungi and protozoans.
- Made up of a large number of cells of different types that are normally specialized in specific functions.
Multicellular organisms are plants or animals and each of them is made up of plant cells or animal cells respectively, which have certain fundamental differences in their structure.
Both animal and plant cells are tiny and the vast majority measure on the order of 1 to 100 microns. That is 1×10-6 meters or one millionth of a meter.
Cell types
The cell is the basic biological, functional and structural unit of any living thing.
There are two basic types of cells: eukaryotes , which contain a well-defined cell nucleus, and prokaryotes , which lack one. In general, eukaryotes are part of large multicellular organisms such as animals, plants or humans, while prokaryotes are only part of single-celled organisms such as bacteria or Archaea.
Prokaryotic cells
Prokaryotic cells were the first living things on Earth and appeared about 3.5 billion years ago.
Their structure is basic so they do not form multicellular organisms and they have these characteristics that distinguish them from eukaryotes :
- Prokaryotic cells are part of the Monera Kingdom, that is, Archaea and Bacteria.
- They are the smallest organisms and their size is between 1-5 micrometers.
- They do not have a defined nucleus and therefore no nuclear membrane.
- DNA is found on a single, normally circular chromosome located in the cytoplasm.
- Ribosomes are also found in the cytoplasm but it does not contain other organelles such as mitochondria, lysosomes, centrioles or vacuoles.
- Living beings made up of prokaryotic cells are called prokaryotic organisms or beings.
- The organization of this type of cells is normally unicellular.
- Its reproduction is by binary fission.
Prokaryotic cells were the first forms of life on earth and their structure and functioning is much simpler than that of eukaryotic cells.
Eukaryotic cells
Eukaryotic cells usually have a complex multicellular organization forming higher organisms, although they can also be part of unicellular organisms.
- They form the organisms of the kingdoms Protista, Plantae, Animalia and Fungi.
- They have a nucleus differentiated from their other parts, covered by a double nuclear membrane.
- Their DNA is found in linear molecules and they have several chromosomes.
- Eukaryotic cells have specialized organelles such as cytoplasm, mitochondria, vacuoles, etc., which can be independently identified inside and are separated by membranes.
- Their size is larger and measure between 10-100 micrometers. They contain mitochondria and in the case of plant cells chloroplasts.
- Its division is by mitosis and meiosis.
- The DNA or genetic material of a eukaryotic cell is contained only in the cell nucleus. Organisms made up of eukaryotic cells are called eukaryotic beings.
Types of organisms
Another typology considers two types of eukaryotic cells depending on the organism to which they belong; in this sense, there are animal cells and plant cells .
The unit of length to measure a cell is the micron or micrometer, which is equivalent to one millionth of a meter 1×10-6.
The largest cells measure up to 4 centimeters and the smallest about 0.5 micrometers.
Parts of the cell
The elementary study of the cell shows that this unit is different in animals and plants. Both have in common the presence of a cell membrane, the cytoplasm, the nucleus and other specialized structures called organelles.
Nucleus – The center of the cell
In both cases, the nucleus contains most of the genetic material in linear DNA molecules. Also, it is the control center of the cell.
The Cell Membrane – The protection of the cell
It has the important mission of facilitating the transport of elements between the cell and its environment, allowing the selective passage of some types of molecules and preventing the passage of others.
It is mainly composed of phospholipids, proteins and carbohydrates.
The Cytoskeleton – The Support of the Cell
It is an important structure that gives support and shape to the cell and keeps organelles in place. It is essential in the growth, movement and reproduction of the cell, as well as in the exchange of substances with the outside world.
The Cytoplasm – The internal space of the cell
The cytoplasm is the The cytoplasm is the structure found between the nucleus and the plasma or cell membrane. Its function is to house the organelles and allow their movement and the transport of substances within the cell.
Organelles – The specialists
The organelles that each type of cell has are different. In the animal cell, there are mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus and centrioles, while plant cells contain chloroplasts, permanent vacuole and cell wall.
Ribosomes – The protein producer
Ribosomes synthesize proteins within cells, a vitally important function which is why many have hundreds or even thousands of ribosomes.
Mitochondria and Chloroplasts – Energy generators
Mitochondria are essential in the generation of energy in eukaryotic cells, which they do through complicated processes. Chloroplasts perform the same function but are only found in plants and are essential in the photosynthesis process.
The Endoplasmic Reticulum and the Golgi Apparatus – The Molecular Managers of the Cell
The endoplasmic reticulum directs certain molecules to specific destinations within the cell where they are modified by certain processes, converting them into proteins that, before being exported, are packaged or modified by the Golgi Apparatus.
Lysosomes and Perixosomes. The digestive system of the cell
These organelles are responsible for processing and disposing of the materials that are required by the cell and to do so they contain digestive enzymes that process proteins. Perixosomes are responsible for disposing of any toxic and waste substances.
History of the study of the cell
The cell is the basic biological, functional and structural unit of any living organism.
The history of the study of the cell begins with Antonie van Leeuwenhoek , considered the father of Microbiology and creator of the Microscope, who also made the first sketches of a protozoan observed in rainwater.
In 1665, the English scientist Robert Hooke published his work Micrographia , which presented for the first time drawings of what he had observed under an optical microscope. It also stands out for having been the work that exposed the word “cell”, coined by Hooke.
“Cell” comes from the Latin word cella, which means “hole” according to the Dictionary of the Royal Spanish Academy. However, the word “cell” refers to the spaces that Hooke observed in a sheet of cork, realizing their resemblance to the cells of honeycombs. Although he is credited as the discoverer of the cell, Hooke was unable to delve beyond the cursory description.
In 1839, Theodor Schwann and Matthias J. Schleiden went down in history by exposing their theory that all living beings are made up of cells, after having carried out different studies.
Over the next few years other scientists shaped cytology, the study of the cell, and some focused on specific aspects. In 1855 Rudolph Virchiow stated that new cells are derived from other pre-existing cells thanks to the process of cell division.
Between 1931 and 1935, Ernst Ruska built and perfected the electron microscope, which made it possible to observe new, previously unknown organelles in the cell.
One of the most important discoveries in the history of Cytology was announced in 1953, when James Watson and Francis Crick discovered the double helix structure of the DNA contained in cells, thus laying the foundations of genetics.