The best replacement for chloroplasts is mitochondria.

The best alternatives to chloroplasts are rated as following:
★★★★★  mitochondria
★★  chlorophyll
★  mitochondria first
★  mitochondria which came first
  chromoplasts
  nuclei larger
  mitochondria chemiosmosis
  plastids
  unboiled chloroplasts
  amyloplasts
  mitochondrion

Your alternative for chloroplasts is not listed? Suggest!
Speaking about chloroplasts, one probably shouldn't forget about chlorophyll.

Other search terms related to chloroplasts and their ratings are:
★★★★★ chlorophyll
You have in mind a companion for chloroplasts and it is not yet here? Propose!



Google Trends

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chloroplasts
mitochondria
chlorophyll