Final answer:
Photosynthesis takes place in the chloroplasts of autotrophic eukaryotes, where the chlorophyll-containing thylakoid membranes perform the light reactions to produce energy-rich molecules.
Step-by-step explanation:
In which organelle does photosynthesis take place? The answer is that photosynthesis occurs inside an organelle called the chloroplast. Chloroplasts are specific to autotrophic eukaryotes, such as plants and algae. They contain a double membrane envelope consisting of an outer and an inner membrane. Additionally, chloroplasts have a third membrane that forms structures called thylakoids, which are stacked into grana. These thylakoids contain chlorophyll, the green pigment that absorbs light and initiates the process of photosynthesis. The light reactions of photosynthesis take place within the thylakoid membranes, leading to the production of ATP and NADPH, which store chemical energy temporarily.