Biology Terminologies

a. Compare mitochondria and chloroplasts with prokaryotes:

There are many physiological evidences showing that mitochondria and chloroplast have a common ancestor with nowaday bacteria. Some of the most plausible evidences are: both mitochondria and chloroplasts have their own protein synthesis mechanism, which is very similar to that of bacteria: they have their ownDNA in the form of a circular loop floating in their internal matrix, both have 70S ribosomes as in bacteria, not the same as the ribosomes in the cytosol of the cell. The outer membranes of Gram-negative bacteria contain porin, which is also found in the outer membrane of chloroplasts and mitochondria.Mitochonria and chloroplasts can only arise from existing structures, because nuclear DNA only codes for a number of proteins required for the formation of them. Those evidences have lead to a hypothesis that mitochondria and chloroplasts originated from acient bacteria via endosymbiosis with acient eukaryotic cells.


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