Chloroplasts are found in the mesophyll cells of leaves and other green parts of a plant.
- Each chloroplast is a discoid or lens-shaped structure bounded by a double membrane envelope.
- The inner space is differentiated into two regions.
- The matrix part of this organelles is called stroma and is filled with proteinaceous fluid containing 70s ribosomes, small circular DNA, osmophilic droplets dissolved salts and several enzymes.
- In the stroma, the region is found lamellar structures which are arranged one over the other like a stack of coins.
- The lamellar structures are thylakoids and this region comprising of lamellar structures is called granum.
- Each chloroplast may contain several grana which remain interconnected by stroma lamellae or frets.
- Photosynthetic pigments, chlorophyll, carotenoids are found in the grana region of a chloroplast. Hence this acts as a site of light reaction of photosynthesis.
- Dark reaction is completed in the stroma region of the chloroplast.
