Inside the Cell

Endosymbiosis refers to the process by which one organism lives inside another and both benefit from the relationship. The most significant example of this in evolutionary history is the origin of eukaryotic cells, which is explained by the endosymbiotic theory. Eukaryotic cells are thought to have evolved from a symbiotic relationship between two or more prokaryotic cells (simpler, single-celled organisms without a nucleus). These organelles—the cell within a cell—are believed to have originated from free-living prokaryotes that were enclosed by a host cell. Where one cell engulfed another, leading to the formation of organelles like mitochondria and chloroplasts. This relationship provided a massive energy boost, enabling the development of complex life forms. This energy surplus likely facilitated more frequent cell divisions and greater organismal complexity. This theory is a cornerstone of our understanding of cellular evolution.


A process—endosymbiosis—where one organism lives within another plays a crucial role in the development of life on Earth. The acquisition of mitochondria and chloroplasts through endosymbiosis marked a significant event in the history of life, as it increased internal energy availability within cells. Mitochondria, often referred to as the "powerhouses of the cell," are responsible for producing adenosine triphosphate (ATP), the primary energy currency of cells, through cellular respiration. This increased energy production allowed for the development of more complex eukaryotic cells, which have a nucleus and organelles. Chloroplasts, on the other hand, are essential for photosynthesis in plants and algae, converting sunlight into chemical energy, thus providing another source of energy for life on Earth.



The increased internal energy availability through endosymbiosis was a pivotal event in the history of life. Specifically, the acquisition of mitochondria and chloroplasts dramatically enhanced energy production and utilization, facilitating the evolution of complex eukaryotic cells. This energetic revolution provided the foundation for the rise of multicellularity, ultimately leading to the remarkable diversity of life forms that exist today.


The enhanced energy availability resulting from endosymbiosis not only advanced life's complexity but also set the stage for the ecological and evolutionary dynamics that continue to shape our biosphere. By providing a more stable and efficient energy source, endosymbiosis allowed for the development of increasingly intricate and interconnected ecosystems, enabling organisms to adapt, evolve, and thrive in a variety of environments.


It is truly remarkable to consider how this energy revolution has impacted the trajectory of life on our planet. As we continue to study the intricacies of the natural world, it is essential to recognize and appreciate the profound role that endosymbiosis has played in the ongoing story of life on Earth.




 

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The Origin of Mitochondria
By: William F. Martin, Ph.D. (Institute for Botany, University of Dusseldorf) & Marek Mentel, Ph.D. (Dept. of Biochemistry, University of Bratislava) © 2010 Nature Education
Citation: Martin, W. & Mentel, M. (2010) The Origin of Mitochondria. Nature Education 3(9):58

Mitochondria arose through a fateful endosymbiosis more than 1.45 billion years ago. Many mitochondria make ATP without the help of oxygen.
https://www.nature.com/scitable/topicpage/the-origin-of-mitochondria-14232356/

Origin of Mitochondria | Learn Science at Scitable

 The idea of endosymbiosis was first proposed by Konstantin Mereschkowski, a prominent Russian biologist, in 1905. He coined the term "symbiogenesis" when he observed the symbiotic relationship between fungi and algae (Mereschkowski 1905). The term "endosymbiosis" has a Greek origin (endo, meaning "within"; syn, meaning "with"; and biosis, meaning "living"), and it refers to the phenomenon of an organism living within another organism.
 https://www.nature.com/scitable/topicpage/the-origin-of-plastids-14125758/

The Origin of Plastids | Learn Science at Scitable