Question

In $PS \, I$ , the reaction centre Chl $a$ has absorption maxima at ______________ ; whereas in $PS \, II$ , the reaction centre Chl $a$ has absorption maxima at ________________.

• A. $700 \, nm, \, 680 \, nm$
• B. $680 \, nm, \, 700 \, nm$
• C. $400 \, nm, \, 500 \, nm$
• D. $700 \, nm, \, 800 \, nm$

Answer 1

Answer: (A)

In the light reaction of photosynthesis, several complexes and pigments are involved that are organised in two distinct light-harvesting complexes, called photosystems I and II. Each photosystem has a single reaction centre (a specific type of chlorophyll a molecule) and various other pigments, that help in the absorption of a wide range of wavelengths of light. They are called antennae molecules. The antennae molecules are made up of many pigment molecules bound to proteins. The antennae molecules increase the efficiency of absorption of different wavelengths of light.
A photosystem is an assembly of 250–400 pigment molecules bound to proteins. Each photosystem has a particular molecule of chlorophyll a that acts as a reaction centre and various other pigment molecules that function as antennae.
In PS I, the reaction centre is P 700 while in PS II, the reaction centre is P 680.