(a) : Photosynthesis occurs in chloroplasts that contain photosynthetic pigments - chlorophylls, carotenoids etc. The light energy required for photosynthesis comes from sunlight. The sunlight travels in the form of small particles called photons. Each photon has a quantum of energy. This quantum of energy is absorbed by a single antenna chlorophyll and then migrates from one molecule to the other till it reaches the reaction center of photosystems. The reaction center is also P700 chlorophyll molecule that releases electron as a result of transferred energy. This electron is transferred between various acceptors and generates ATP and NADPH ‌2 in the light reaction of photosynthesis.