Células Procariotas: Características, Estructura, Función y Evolución

Study Notes

Prokaryotic Cells: Characteristics, Structure, Function, and Evolution

Prokaryotic cells are unicellular organisms belonging to the domains Bacteria and Archaea. These cells are smaller than eukaryotic cells and lack a nucleus and organelles. Despite their simplicity, prokaryotes play a crucial role in various ecological niches and are essential for maintaining global biogeochemical cycles.

Characteristics of Prokaryotic Cells

Structure

Prokaryotic cells come in various shapes, including spherical (cocci), rod-shaped (bacilli), and spiral-shaped (spirilli) forms. They are surrounded by a plasma membrane, cytoplasm, ribosomes, and a cell wall. Some prokaryotes may have additional structures like a capsule, flagella, and pili.

Function

Prokaryotes have a single circular chromosome in a region called the nucleoid. They do not undergo mitosis or meiosis but reproduce asexually through binary fission.

Evolution

Prokaryotes evolve through mechanisms such as transformation, transduction, and conjugation, which allow them to exchange genetic material with other prokaryotes.

Genetic Material

The genetic material of prokaryotes is DNA, which is found in the cytoplasm of the cell and not surrounded by a nuclear membrane or proteins.

Reproduction

Prokaryotic reproduction is typically asexual, with DNA replication and cell division occurring in the cytoplasm. Binary fission is the primary means of reproduction.

Prokaryote Structure

Cell Wall

Prokaryotes have a cell wall outside the plasma membrane, which contains peptidoglycan in bacteria and is absent in archaea. The cell wall provides structural support and protection against external factors.

Cytoplasm and Membrane

The cytoplasm of prokaryotic cells is a jelly-like substance that contains enzymes, ions, and other cellular components. The plasma membrane regulates the entry and exit of substances into the cell.

Capsule

Some prokaryotes have an outer capsule, which can help the cell attach to surfaces, protect from dehydration, and provide resistance to phagocytic cells and host immune responses.

Structures for Movement

Prokaryotes may have flagella for locomotion, pili for DNA exchange, and fimbriae for adhering to surfaces.

Nucleoid

The genetic material of prokaryotes is located in a region called the nucleoid, which is not surrounded by a nuclear membrane.

Prokaryotic Evolution

Prokaryotes evolved from a common ancestor that lived approximately 3.5 billion years ago. They diversified into two main groups, Bacteria and Archaea, which have distinct cell wall compositions and membrane structures.

Prokaryotic Genetics

Prokaryotes have a single circular chromosome that is replicated and separated during binary fission. They can also exchange genetic material through mechanisms such as transformation, transduction, and conjugation.

In summary, prokaryotic cells are small, single-celled organisms that play a vital role in various ecosystems. They lack a nucleus and organelles, but possess a plasma membrane, cytoplasm, ribosomes, and a cell wall. Prokaryotes reproduce asexually through binary fission and have a single circular chromosome. They have evolved different cell wall compositions and membrane structures, leading to the division into the domains Bacteria and Archaea.

Description

Explora las características, estructura, función y evolución de las células procariotas, incluyendo su reproducción asexual, genética y diversificación en las dominios Bacteria y Archaea. Aprende sobre la importancia de estos organismos unicelulares en los ciclos biogeoquímicos globales.