11. Per the radical pair mechanism photopigments absorb a photon, which elevates it to the singlet state. 12. It is yet unknown how the animals that gain a new photopigment are perceiving the new color. 13. The human peripheral retina senses light at high intensities that is best explained by four different photopigment classes. 14. "' Photopigments "'are unstable pigments that undergo a chemical change when they absorb light. 15. The reaction of this single photopigment will give the same quanta for 400 nm light and 700 nm light. 16. Carotenoids and photopigments both indirectly act as photo-protective pigments, as they quench oxygen free-radicals. 17. The xanthophyll cycle takes place, along with other photopigment reactions, in the membranes of thylakoids within chloroplasts. 18. Photopigments exist as transmembrane proteins within these disks, which provide more surface area for light to affect the pigments.19. Cryptochromes, a class of photopigments known from plants and related to photolyases, have been suggested as receptor molecules. 20. The encoded protein is called red cone photopigment or long-wavelength sensitive opsin ( LWS opsin or L opsin ).
