Which of these was not derived from an ancestral alpha proteobacterium?
mitochondrion
kinetoplast
chloroplast
hydrogenosome
mitosome
To determine which of these options was not derived from an ancestral alpha proteobacterium, we need to understand the evolutionary origins of these structures.
The endosymbiotic theory suggests that mitochondria, chloroplasts, and some other organelles in eukaryotic cells were once free-living prokaryotes that were engulfed by ancestral eukaryotic cells. These prokaryotes eventually established a mutualistic relationship with the host cell, leading to their integration and specialization as organelles.
Mitochondria, which are involved in energy production through aerobic respiration, are generally believed to have originated from an ancestral alpha proteobacterium. Similarly, chloroplasts, involved in photosynthesis, likely originated from an ancestral cyanobacterium.
Kinetoplasts are unique structures found in certain single-celled eukaryotes called trypanosomatids. These organisms belong to the excavate supergroup and have a distinctive DNA structure within their mitochondria called a kinetoplast. However, kinetoplasts are not derived from alpha proteobacteria but rather involve specific modifications to the mitochondrial genome within these organisms.
Hydrogenosomes and mitosomes are organelles found in certain anaerobic eukaryotes. These organelles have lost most of their function and are reduced versions of mitochondria. Hydrogenosomes are involved in hydrogen production, while mitosomes are involved in specific metabolic processes. Although they share some similarities with mitochondria, they are thought to have evolved independently from mitochondria and are not derived from alpha proteobacteria.
Therefore, among the given options, the structure that was not derived from an ancestral alpha proteobacterium is the mitosome.