Chloroplast are lens shaped cell organelles located in the mesophyll cells. The chloroplast is bounded by a double membrane separated by the intermembrane space. The centre encloses a homogeneous gel-like fluid called stoma or matrix. It has 50% of the chloroplast proteins, Ribosomes, DNA and enzymes of dark reaction.
The matrix has a system of lamellae differentiated as grana lamellae made of flattened sacs called thylakoids arranged as a stack of coins. The thylakoid membrane has an outer stromal surface and an inner luminal surface in contact with the thylakoid lumen. Some of the lamellae are unstacked and connect the grana called stroma lamellae or inter grana lamellae. The grana lamellae form the site for light reaction and stroma form the site for a dark reaction.
