<human>:  With respect to carotenoids, how many different types of carotenoids are there?
<bot>: There are about 600 different carotenoids. They are all derived from the same basic structure, but they vary in the number of double bonds they have. Some of the most common carotenoids are beta-carotene, alpha-carotene, lycopene, lutein, and zeaxanthin.