Final answer:
Chloroplasts, and specifically the chlorophyll within the thylakoid membranes, are responsible for trapping sunlight during photosynthesis.
Step-by-step explanation:
In the process of photosynthesis, the part of the plant cell responsible for trapping sunlight is the chloroplast. Specifically, molecules of chlorophyll, which are pigments located within the thylakoid membranes of the chloroplasts, absorb the energy from sunlight. This is vital for the light-dependent reactions of photosynthesis, initiating the process that ultimately leads to the production of glucose for the plant.
The light-independent reactions of photosynthesis, also known as the Calvin cycle, occur in the stroma of the chloroplasts. The stroma is the dense fluid that surrounds the thylakoid membranes within the chloroplast. It is where carbon dioxide is fixed into sugars using the energy captured by chlorophyll during the light-dependent reactions.