Did the ancestral eukaryotic cell with its nucleus and other organelles evolve first and then some eukaryotes got mitochondria or did the ancestral eukaryotic cell have mitochondria, according to SET?
According to SET mitochondria evolved first and the fact that almost all eukaryotes have mitochondria supports this suggestion
It is believed that bacteria (prokaryotes) form a symbiotic relationship with eukaryotic cells. Theses small prokaryotes became a part of eukaryotes becoming the powerhouse. The powerhouse of the cukaryotic cells are known as mitochondria.
According to the Serial Endosymbiotic Theory (SET), the ancestral eukaryotic cell did not have mitochondria initially. Instead, SET proposes that mitochondria originated from free-living bacteria that were engulfed by an ancestral host cell in a process called endosymbiosis.
To explain how the ancestral eukaryotic cell acquired mitochondria, let's break it down into steps:
1. Step one: The first eukaryotic cell, which had a nucleus and other organelles, originated through a process called endosymbiosis. This involved the engulfment of a smaller prokaryotic cell by a larger host cell, leading to the establishment of a symbiotic relationship.
2. Step two: The prokaryotic cell that was engulfed eventually evolved into what we now call the mitochondrion. This symbiotic relationship between the host cell and the engulfed prokaryote was mutually beneficial. The host cell gained energy and metabolic benefits, while the engulfed prokaryote gained a protected and stable environment.
3. Step three: Over time, the engulfed prokaryote and host cell became increasingly interdependent. The prokaryote specialized in providing energy-related functions, such as generating ATP through cellular respiration, while the host cell provided protection and nutrients to the prokaryote.
4. Step four: Through a process of genetic integration, the ancestral host cell and the engulfed prokaryote developed a cohesive unit, where the prokaryote's genetic material was incorporated into the host cell's nucleus. This integration allowed for the coordination of cellular functions and the evolution of a more efficient eukaryotic cell.
In summary, SET proposes that ancestral eukaryotic cells did not possess mitochondria originally. Instead, mitochondria were acquired through endosymbiosis, where a prokaryotic cell was engulfed and eventually evolved into the mitochondrion we see in eukaryotic cells today.