Answer the following question given this paragraph: 

The chloroplast is the site of photosynthesis. Part of the photosynthesis reactions occur in an internal membrane within the organelle. The chloroplast contains many of these internal membranes, making photosynthesis very efficient. These internal membranes stack on top of each other, just like a stack of pancakes.


Q: What structure, containing many internal membranes, is the site of photosynthesis?


A:
chloroplast