Here's why:

* Chloroplasts are organelles found in plant cells and some algae.

* They contain chlorophyll, a green pigment that absorbs sunlight.

* Photosynthesis takes place within the chloroplast, where sunlight is converted into chemical energy in the form of glucose (sugar).

While other cell parts play roles in supporting the process, like the cell membrane for transporting materials and the nucleus for DNA, it is the chloroplast that is specifically responsible for the actual process of photosynthesis.