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, 680nm
b. 680nm, 700nm
c. 400nm, 500nm
d. 700nm, 800nm

Answer 1

Hint: Photosystems are present in the thylakoid membranes of algae, cyanobacteria, and plants. Photosystems consist of many pigments that help in collecting light energy and a special pair of chlorophyll molecules found at the reaction center of photosystems.

Complete answer:
- Photosystems are the protein complexes that are involved in the process of photosynthesis.
- Each photosystem has its own wavelength of light to which its reaction center is most reactive.
- The photosystem I (PSI) reaction center is known as P700 where ‘P' is the pigment and ‘700' is for the wavelength of light that is absorbed more strongly by this particular chlorophyll molecule.
- The reaction center of photosystem II (PS II) is known as P680, where P stands for photosystem, and 680 is the wavelength of light absorbed by the chlorophyll molecule.
- Photosystems consist of many pigments that help in collecting light energy and a special pair of chlorophyll molecules found at the reaction center of photosystems.

Hence, the correct answer is option (A).

Additional information:
- During the process of photosynthesis, Photosystem ll comes before Photosystem I.
- In the electron flow, Photosystem II precedes Photosystem I.
- The product of Photosystem I is ATP.
- Photosystem II produces oxygen.
- PS l absorbs the longer wavelength of light whereas PS II absorbs the shorter wavelength of light.

Note: Photosystem I and photosystem II are the protein complexes that consist of pigments that are necessary to harvest protons and they use light energy to catalyze the photosynthetic endergonic reactions producing high energy compounds. Photosystem I is used to produce NADPH which is high energy carriers. Photosystem II is responsible for oxygen evolution, plastoquinone reduction, and water splitting. Plastoquinone plays a role in photosynthesis.