What is a cell?

We explain what the cell is and what types of cells exist. In addition, what are the parts and functions of the cells.

1. What is a cell?

The smallest and simplest form of biological organization is known as a cell , that is, the smallest known living and orderly structure (most viruses are smaller than a cell, but there is a discrepancy regarding their origin and whether or not they are “living beings”).

All cells meet the requirements of nutrition , relationship and reproduction , and can constitute living beings in themselves, called unicellular ; or through huge and diverse colonies that interact in an orderly manner, called multicellular beings . This according to the cellular theory proposed and updated by successive generations of scientists throughout the seventeenth, eighteenth, nineteenth and twentieth centuries (although considered as true only since 1838), which indicates that there are no known living beings that are not constituted by the least one cell

The size of the cells can vary greatly, some of which can be practically visible to the naked eye , while others are microscopic. Its average size is about 10 µm (micrometers). Its reproduction occurs based on two possible mechanisms: sexual (exchange of genetic information) or asexual (mitosis, similar to cloning ).

Inside the cells there are organelles , even simpler structures that keep walking the various biochemical functions necessary for their survival and functioning.

The discovery of the cell is considered the foundational step of the modern study of life ( biology ), since it allowed us to understand the enormous complexity of the body of living beings and allowed the emergence of numerous later sciences and disciplines.

2. Cell types

The most important classification of cells has to do with the presence or absence of a cell nucleus . This distinction is fundamental in the history of evolution, since it makes it possible to distinguish the two great superreines or domains of living beings:

• Prokaryotes . Unicellular and nucleus-free living beings, whose genetic material is dispersed inside the cell ( cytoplasm ). They are much simpler organisms.
• Eukaryotic . Unicellular or multicellular living beings whose cells exhibit a defined nucleus, where their genetic material is contained. They constitute a step forward in the specificity of life, with respect to prokaryotes , allowing a greater range of life complexity.

3. Parts of a cell

The cells have different organelles and delimited sectors, such as:

• The membrane plasma . A biological border that delimits the cell and distinguishes its interior from the outside, among whose properties is that of allowing the entry and exit of substances. Thus, you can let in certain nutrients and excrete your waste.
• Cell wall . Present in only plant and fungal cells, it is an additional wall to the plasma membrane , which gives them some stiffness and resistance, and made of resistant materials, such as polymers.
• Core . As stated, it is not present in all cells, but when it is, it contains all of its genetic material ( DNA ).
• Cytoplasm . This is called the inside of the cell, its “body.” It consists of water and other substances, and accommodates the different organelles.
• Organelle . These are the “organs” of a cell, which play specific roles. The most common are:
  • Mitocondias . They are responsible for providing energy to the cell.
  • Lysosomes . They deal with the digestion and utilization of nutrients.
  • Chloroplasts . Unique to the plants, they house the essential chlorophyll for photosynthesis .
  • Ribosomes . They deal with the synthesis of proteins , a necessary process for cell growth and reproduction.
  • Scourge . Certain cells possess these organelles, used to propel themselves in the environment , typical of unicellular beings or mobile cells such as sperm.

4. Functions of a cell

Cells can have very diverse and complex functions:

• Structural functions , that is, of tissue construction, such as fat, muscle and bones, that support the body and its organs.
• Secretory functions , that is, the generation of essential substances for life and the self-regulation of the organism, as do the mucous membranes or glands.
• Metabolic , or energy management functions. They fulfill the role of breaking down nutrients or transporting them throughout the body, as do digestive cells in the intestine and red blood cells in the blood respectively.
• Defensive functions , that is, to cleanse the body and defend it from the presence of external agents or diseases, as do white blood cells.
• Control functions , as in the case of neurons , which coordinate the diverse processes of the body, transporting information and generating specific reactions to specific stimuli.
• Reproductive functions , that is, whether combined with others from another organism of the same species, or perhaps on their own, produce a new cell or a new individual, endowed with a genetic mixture in the first case (such as ovules and sperm) or the same identical DNA in the second ( mitosis ).