FIGURE 12-37 Structure of leaf and chloroplast. Like mitochondria, plant chloroplasts are bounded by two membranes separated by an intermembrane space. Photosynthesis occurs on a third membrane, the thylakoid membrane, which is surrounded by the inner membrane and forms a series of flattened vesicles (thylakoids) that enclose a single interconnected luminal space. The green color of plants is due to the green color of chlorophyll, all of which is located within the thylakoid membrane. A granum is a stack of adjacent thylakoids. The stroma is the space between the inner membrane and the thylakoids.

[From Katherine Esau, D-120, Special Collections, University of California Library, Davis.]