Chloroplasts - found only in plants and algae. they convert solar radiation energy to chemical energy usable for the cell's metabolism.
mitochondria - found in both plants and animals, they produce energy (in the form of ATP - chemical compound) by decomposing sugars and fats. they use up oxygen to do it.
They train our immune system so it's ready when our bodies are attacked, and they aid in digestion and supply us with vitamins. ... Scientists and doctors can even utilize prokaryotes to help the human body.