They may be chloroplasts, chromoplasts, and leucoplasts. A chloroplast is a plastid that contains high amounts of green pigment, chlorophyll. The chlorophyll pigments may be chlorophyll a, chlorophyll b, chlorophyll c, chlorophyll d, and chrlorophyll f. Chlorophyll a is present in all chloroplasts. Other pigments that may be present (particularly in algal cells) are carotenoids and phycobilins. The chloroplast has at least three membrane systems: outer membrane, inner membrane, and thylakoid system. The thylakoids are disk-shaped structures that function as the site of photosynthesis. It is because embedded in the thylakoid membrane is the antenna complex consisting of proteins, and light-absorbing pigments, including chlorophyll (the green pigment) and carotenoids.