Photosynthesis is a vital and complex biochemical process that occurs in the reaction centers of the chloroplast thylakoid membranes in plants. There are two reaction centers – PSII and PSI. PSII establishes proton gradient, creates oxygen and releases electrons that are subsequently transferred to PSI. Photosystem protection mechanisms allow a balanced energy transfer between reaction centers and an optimal electron flow. Due to its built PSII is susceptible to oxidation that leads to a loss of function. Accessory and protective pigments such as carotenoids have a great contribution in stopping oxidation. Carotenoids were first developed in early bacteria and now they are present in all domains, both in photosynthetic and non-photosynthetic organisms. Carotenoids, chlorophylls and proteins together form antenna complexes that are used to harvest light and transfer its energy on the reaction centers. The role of carotenoids in antenna complexes is that of accessory pigments harvesting energy and transferring it on chlorophyll a molecules. Besides being accessory pigments, as protective pigments they have a role in protecting reaction centers from oxidation. Due to their linear molecular structure that contains multiple conjugated double bonds, called piconjugated system, they can either transfer absorbed energy toward chlorophyll a reaction center molecule or accept excess reaction center energy. They can also stop the damage from reactive oxygen species on reaction centers and thylakoid membranes due to their antioxidative abilities. Protection from oxidative damage of photosystem is mainly provided by xanthophyll cycle. Main components of the cycle are quite known but the actual biophysicalmechanism is not yet derived.