Bacteria have no membrane-enclosed organelles. however, some still generate atp through cellular respiration. where is the electron transport chain found in these organisms?

Plasma membrane.

Explanation:

Bacteria plasma membrane is made up of phospholipids bilayer, and have all the general functions such as permeability barrier for molecules, for the molecules serving the location into the cell, and helps to store the energy in the form of ATP.

In bacteria electron transport chain helps in transfer electrons with the help of redox reaction from electron donors to electron acceptors, and couple this with the transfer of protons across the plasma membrane. This process creates an electrochemical proton gradient which helps in the synthesis of ATP.