What enzyme phosphorylates ADP to make ATP

Is it Pi? Is that even an enzyme? Thanks

There are a few that phosphorylate ADP into ATP, but one of the more significant ones is the enzyme called (creatively enough) ATP Synthase, which is located in the Electron Transport Chains of both the inner mitochondrial membrane for cellular respiration and in the thylakoid (I think?) membrane in chloroplasts right after Photosystem II.

Pi is NOT an enzyme, Pi just stands for "inorganic phosphate" and it is what is added to ADP (adenosine DIphosphate) to become ATP (adenosine TRIphosphate). When you phosphorylate something, you are adding Pi.

There are many enzymes that catalyze the phosphorylation if ADP to produce ATP. The main production of ATP occurs during oxidative phosphorylation in the mitochondrion during which the enzyme ATP synthase catalyzes the reaction with energy input from a proton motive force. A similar process also occurs in the chloroplast of plants during photosynthesis. ATP is also produced in glycolysis with the reaction catalyzed by phosphoglycerate kinase and pyruvate kinase.