AP BIOLOGY

Detailed explanation-1: -Inside a chloroplast, thylakoid has two structural forms. One is stroma thylakoid (stroma lamellae), which is a membrane-bound structure embedded into the stroma of chloroplast. The other is granum, which is a well-packed stack of thylakoids (see Figure 1).

Detailed explanation-2: -Thylakoids are pouch-like sacs that are bound to a membrane in the chloroplasts of a plant cell. They contain a pigment, called chlorophyll, that absorbs light. The light absorbed is used in photosynthesis and other processes that are light-dependent. Thylakoids are stacked inside the chloroplast.

Detailed explanation-3: -The thylakoid membranes contain chlorophyll and other pigments arranged in antenna arrays to capture light energy for two photosystems called photosystem I and photosystem II. However, the thylakoid membranes do not contain the Calvin cycle enzymes.

Detailed explanation-4: -The main difference between thylakoid and stroma is that thylakoid is the flattened sac inside the chloroplast where photosynthesis occurs whereas stroma is the fluid-filled, internal space of the chloroplast. Thylakoid and stroma are two important structures of the chloroplast.