In which part of the chloroplast do photosynthetic pigments primarily occur?

Photosynthetic pigments, such as chlorophyll, primarily occur in the thylakoid membranes of the chloroplasts. These membranes are organized into structures called thylakoid sacs, which are stacked to form grana. The thylakoid membranes play a critical role in the light reactions of photosynthesis, as they house the pigment molecules that capture light energy.

When light is absorbed by chlorophyll and other pigments located in these membranes, energy is transferred to the photosystems, which are involved in the conversion of solar energy into chemical energy. This process leads to the synthesis of ATP and NADPH, which are essential for the subsequent reactions of the Calvin cycle that occur in the stroma.

While the stroma is the fluid-filled space surrounding the thylakoids and contains enzymes for the light-independent reactions of photosynthesis, the pigments themselves do not occur there. Chlorophyll is a specific type of photosynthetic pigment found within the thylakoid membranes. Granum refers to the stacks of thylakoids and is not a location of pigment concentration per se but rather a structural feature within the chloroplast.