Granum is a structure found within the chloroplasts of plant cells. It consists of stacked thylakoid membranes, which contain chlorophyll, the pigment responsible for capturing light energy during photosynthesis. The arrangement of granum allows for efficient light absorption and energy conversion. In the process of photosynthesis, granum plays a crucial role in the light-dependent reactions. Here, sunlight is converted into chemical energy in the form of ATP and NADPH, which are then used in the light-independent reactions to produce glucose. This process is essential for the growth and energy needs of plants and other photosynthetic organisms.