Question

Photosynthetic pigment phycobilin is not associated with
A) PS- II
B) Cyanobacteria
C) PS- I
D) All of the above

Answer 1

Hint:PS-I and PS-II stand for photosystems 1 and 2 respectively. The Phycobilins are unique among the photosynthetic pigments in that they are bonded to certain water-soluble proteins, known as phycobiliproteins.

Complete Answer:
1) Phycobilins are the group of photosynthetic pigments found in red algae and cyanobacteria. They are protein linked pigments hence, are called phycobiliproteins. Like chlorophylls, phycobilins are tetrapyrroles but do not contain magnesium and phytol chains. These are found inside sub-microscopic structures called phycobilisomes attached to thylakoids. The light energy harvested by these pigments is not directly utilized but is transferred to chlorophyll a in the manner similar to carotenoids.
2) Phycobilisomes are responsible for splitting of water and produce oxygen by passing light energy to photosystem II. While many photosynthetic eubacteria possess photosystem I to oxidize reduced molecules such as H2​S, only cyanobacteria have photosystem II. The evolution of photosystem II apparently occurred in cyanobacteria.
As we can see, the pigment phycobilin doesn’t take part in the biochemical processes in photosystem-I.

Hence, the correct answer is option C (PS- I).

Additional information:
Green plants have two types of photosynthetic units called photosystems or pigments systems I and II. Each photosystem contains 250–400 pigment molecules. The pigments are organised into two light harvesting complexes or antennae within photosystem I and photosystem II.
The pigments help to make photosynthesis more efficient by absorbing the different wavelengths of light. The single chlorophyll a molecule forms the reaction centre

Note:In PS II, the reaction centre chlorophyll a absorbs 680 nm wavelength of red light which excites the electrons. They jump into an orbit farther from the atomic nucleus.