Chloroplasts contain multiple structures, including the membrane envelope, stroma, grana, thylakoid membrane and chlorophyll. Choloroplasts are the organelles within plant cells where photosynthesis takes place.
The membrane envelope consists of an inner and outer membrane that provides a seal of sorts, enclosing the chloroplast. The stroma is the thick fluid inside the membrane envelope. This is where carbohydrates are converted to energy. The grana is a stack of thylakoid sacs, vital to the process of photosynthesis. The thylakoid membrane consists of individual thylakoids, which is where energy from the sun is converted into energy the plant can use. Chlorophyll is the structure that absorbs energy from the sun, providing food to the plant.