Mitochondria and thylakoid membranes are both responsible for the synthesis of energy in the form of adenosine triphosphate, commonly referred to as ATP. Mitochondria are present in all living cells, and they produce energy through the citric acid cycle. Thylakoid membranes are present within chloroplasts found in plants and produce energy through a process called photosynthesis.
Mitochondria and chloroplasts are both organelles found within living cells. All living organisms contain mitochondria, but chloroplasts are only present in plant cells. Animals produce energy by breaking down the glucose found within food sources. Cells then transport the broken-down components to the mitochondria and incorporate them into the citric acid cycle to generate electrons, which then pass to the electron transport chain to create a proton gradient that ultimately generates water and ATP. Scientists call this process oxidative phosphorylation. The ATP generated provides fuel for the cell.
The light reaction of photosynthesis occurs within the thylakoid membranes of chloroplasts in plant cells in a similar fashion to oxidative phosphorylation. In the light reaction, the cell absorbs a photon and passes the electrons to two photosystems present within the thylakoid membranes. The excited electron then undergoes a oxidation-reduction reaction that ultimately generates ATP and molecular oxygen.