Flat discs inside chloroplasts that are arranged in stacks are called (2) (3) are light-absorbing substances that are inside chloroplasts. They absorb light of different (4) . The green pigment in plants that is essential for photosynthesis is (5) . Light energy absorbed by this pigment excites (6) . They are transferred to a(n) (7) . Then they move down an electron transport chain.

Flat discs inside chloroplasts that are arranged in stacks are called (2) __thylakoids_. (3) __Pigments__ are light-absorbing substances that are inside chloroplasts. They absorb light of different (4) __wavelenghs__. The green pigment in plants that is essential for photosynthesis is (5) __Chlorophyll __. Light energy absorbed by this pigment excites (6) electrons___. They are transferred to a(n) (7) _Electron Carrier_. Then they move down an electron transport chain.

Explanation:  

The chloroplasts are limited by an outer membrane and an inner one.  In the middle of the two membranes, there is a space left called intermembrane space. In the interior of the inner membrane, there is another space known as the stroma. Within the stroma, there is the third system of membranes, known as thylakoids. They are disk-shaped structures, limited by a membrane, and in their interior, there is a space named thylakoid space.

Thylakoids are arranged as piles, receiving the name of grana. Grana connect to each other by a longer thylakoid membrane. The photosynthetic pigments are placed in the thylakoids, where it occurs light-dependent reactions. These molecules are in charge of light absorption. The most common pigment is chlorophyll, which provides the typical green color of plants. When sunlight reaches the pigments, electrons get excited and move along the electron transport chain, places in the thylakoid membrane.  This process occurs during photosynthesis, while new electrons provided by water molecules replace the excited ones. The final products are oxygen, ATP, and NADPH.  

In the stroma, it takes a place the Calvin cycle.