Answer:
On the inner portion of the plasma membrane
Explanation:
Prokaryotic cells lack nucleus and membrane-bound organelles such as mitochondrion, nucleus and chloroplasts. ATP is necessary for the existence of all living organisms and it is synthesized during the process of respiration.
In eukaryotic cells, ATP is synthesized on the inner membrane of the mitochondrion known as cristae. Because prokaryotes lack mitochondrion, ATP generation is carried out on the inner portion of the plasma membrane. It contains all the relevant enzymes for ATP production and adjusts its shape to do so when necessary.