Posted: February 1st, 2023
Prokaryotes are unicellular and diverse organisms. They include bacteria and archaea. They lack cell organelles and an enveloped nucleus. However, they still perform a wide variety of metabolic reactions. These reactions are also part of biogeochemical cycles. These metabolic reactions help them to act as mediators for recycling of inorganic elements such as nitrogen, carbon, sulfur, and so on between living and non-living matter. Photosynthesis by photoautotrophs like cyanobacteria helps them to participate in the carbon cycle.
A prokaryote is a unicellular organism that lacks a nucleus enclosed by an envelope.
In the three-domain system, prokaryotes are divided into two domains based on molecular analysis: Bacteria (Eubacteria) and Archaea (Archaebacteria).
In the third domain, Eukaryota, organisms with nuclei are positioned. Prokaryotes are thought to have arisen before eukaryotes in the study of the origins of life.
Prokaryotes lack cell organelles and compartment systems like a eukaryotic cell.
Some prokaryotes, such as cyanobacteria, may form large colonies while typically being unicellular.
In their life cycles, others, like myxobacteria, have multicellular stages.
There are several elements in the prokaryotic cell that enable it to act as a living organism.
First, the prokaryotic cells are covered with a cell membrane that enables them to create within the cytosol a specific environment that permits biochemical reactions to happen.
Secondly, both loose DNA and ribosomes harbor the cells. Though ribosomes are considered as cell organelles that are not bound to the plasma membrane.
DNA and ribosomes perform the biological metabolism to produce the proteins that are needed by the cells to absorb nutrients, reproduce, and to protect themselves from predators or changes in the environment.
Prokaryotic cells are significantly smaller in size than eukaryotic cells. In general, because it is packed with fewer DNA molecules to create the proteins needed to make an ultra-efficient membrane, a prokaryotic cell is smaller.
The cells thus reach a size when the number of nutrients that are required by the cytosol can no longer be imported. It is referred to as the â€˜limit of the surface-area-to-volume ratioâ€™.
However, because they undergo biochemical reactions actively within their cells, bacteria are much larger than viruses.
Prokaryote and metabolic diversity based on energy and carbon sources:
Prokaryotes are organisms that are metabolically diverse.
With differences in the energy and carbon sources and conditions, there are many different environments on Earth.
By using whatever energy and carbon sources are available, prokaryotes have been able to adapt to every kind of environment.
Prokaryotes enhance the many niches on the Earth, including nutrient cycles such as cycles of nitrogen and carbon, dead organisms decomposing, and living organisms, including humans, flourishing inside it.
Since they have varied metabolic processes, the very wide range of environments that prokaryotes occupy is possible.
In order to group prokaryotes, two major nutritional requirements are involved. These are (1) the metabolism of carbon, the source of carbon for the construction of organic cell molecules, and (2) the metabolism of energy, the source of energy used for growth.
Based on carbon metabolism, they are of two types- heterotrophs and autotrophs.
Based on energy metabolism, they are of six types- phototrophs, chemotrophs, photoheterotrophs, chemoheterotrophs, photoautotrophs, and chemoautotrophs.
Metabolic activity in prokaryotes:
As a result of their varied metabolisms, prokaryotes play vital roles in several biogeochemical cycles such as sulfur cycle, nitrogen cycle, carbon cycle, and so on.
There are metabolic pathways for some bacteria that enable nitrogen and sulfur to be metabolized in unique pathways not known to the eukaryotic cells.
Deep-sea ecosystems nurture several prokaryotes that can metabolize sulfur.
Hydrogen sulfide from steaming hot hydrothermal vents can oxidize certain prokaryotic species.
In a process called chemosynthesis, the inorganic carbon which is present in the water molecules is fixed using energy to synthesize carbon as sugars and other organic molecules.
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