Answer:
The electron transport system is located in the cell membrane in bacteria, while in eukaryotes it is located in the mitochondrial cristae
Explanation:
Endosymbiosis is the hypothesis that complex organelles ( chloroplast and mitochondria) within the cell came from other living organisms. That is, they originated because one cell ingested another cell. A proof of this is that these organelles have their own genome and their own transcription and translation system. Their genome is independent of the genome within the nucleus of the cell.
The genome of the mitochondria is specialized in the electron transport system. The ingestion of a cell (i.e. bacteria) with such genome could bring evolutionary advantages to the to the ingesting cell over other cells without the mitochondrial genome.