Anatomy of Chloroplasts

In plants, photosynthesis takes place within the leaf's dense mesophyll cell layers where the highest number of chloroplasts is contained.

Scattered throughout these specialized double membrane organelles are another set of compartments. Fluid filled membranous sacs called thylakoids, which are interconnected and form into multiple stacks called grana.

On the outer edges of each granum, embedded within the thylakoid membranes, are multiprotein complexes such as the photosystems. These structures contain the antenna proteins bound with numerous pigment molecules, like chlorophylls, to absorb light and begin the first stage of light dependent reactions.

Meanwhile the second stage, the Calvin cycle, takes place in the stroma, the aqueous cavity outside of the thylakoid's lipid bi-layer. With both processes working together, plants produce their own food thanks to the biochemical factories found in the chloroplast.