Diffusion occurs because of the movement of molecules from
the region of higher concentration to the region of lower concentration. This
movement of molecules occurs due to a thermal motion. Diffusion normally occurs
between two compartments having difference in concentration. In case of fluid
it moves from the region of higher concentration to the region of concentration
until a balance is reached. The process of diffusion is very important for the
humans as well. The oxygen that humans breathe in gets diffused with the blood.
In light-dependent reactions, the energy from sunlight is absorbed by chlorophyll and converted into chemical energy in the form of electron carrier molecules like ATP and NADPH. Light energy is harnessed in Photosystems I and II, both of which are present in the thylakoid membranes of chloroplasts.
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