Final answer:
The antenna complex of a photosystem captures light energy and transfers it to the reaction center's chlorophyll a molecules, initiating the light-dependent reactions of photosynthesis.
Step-by-step explanation:
The antenna complex of a photosystem serves a crucial role in the process of photosynthesis by capturing light energy. Each photosystem contains a light-harvesting complex, which includes multiple antenna proteins that contain a mixture of 300-400 chlorophyll a and b molecules as well as other pigments like carotenoids. The main function of the antenna complex is to capture light energy and transfer it to two special chlorophyll a molecules in the reaction center. This energy is then used to excite an electron from the chlorophyll a pair, which is subsequently passed to the primary electron acceptor. While the antenna complex itself does not convert this energy into chemical form, nor does it extract electrons from water or pass electrons to the photosynthetic electron transport chain, it does play an essential role in the initial steps of the light-dependent reactions of photosynthesis by ensuring the necessary energy is provided to drive these reactions forward. In short, the correct option is c) It captures light energy.