Question

Which of the following is the characteristic of PS-1?
A. It is active only up to 680nm of light
B. The reaction center of PS-1 is P680
C. PS-1 is reduced by electrons released in the photolysis of water
D. PS-1 is involved in non-cyclic photophosphorylation

Answer 1

Both PS1 and PS2 systems absorb the different wavelengths of light. Both PS1 and PS2 work the same as mitochondria of animal cells in which electron transport occurs via the electron transport system resulting in the formation of ATP.

Complete answer: The lamellar membrane of chloroplast have 2 pigment-protein complexes:
Photosystem-1
Photosystem-2
PS-I is located in non-appressed regions of grana and stroma thylakoids while PS-II is found only in appressed regions of grana thylakoids. The PS1 is the pigment-protein complex which in presence of light can induce a weak oxidant that oxidizes plastocyanin and also induce a strong reductant that transfers electrons to ferredoxin. The core complex of PS-I is made up of a special type of pigment molecules similar to chlorophyll-P700 which absorb the wavelength of 700 nm, two iron-containing chlorophyll proteins similar to ferredoxin, called Fe-S proteins. Thus core complex of PS-I contains P700, which represents its reaction center. Photophosphorylation is the process by which chlorophyll produces ATP when exposed to light. Photophosphorylation involves 2 pathway cyclic and non-cyclic.
Option-A-It is active only up to 680nm of light: In PS1, the absorption of light energy takes place by pigment molecules that absorb wavelength exceeding 680nm. So it can not be up to 680nm because they contain pigments that can only absorb above 680nm wavelength.
Option-B-The reaction center of PS-I is P680: The reaction center of PS-I is P700 and the reaction center of PS-II is P680.
Option-C-PS-I is reduced by electrons released in the photolysis of water: Photolysis of water occurs in PS-II. This is the process in which water lysed by unknown compound Z which produces electron for the reaction center of PS-II.
Option-D-PS-I is involved in noncyclic photophosphorylation: Non-cyclic photophosphorylation involves both PS-I and PS-II.
So, the right answer is, Option-D-"PS-I is involved in non-cyclic photophosphorylation"

Note: PS-I and PS-II pigment systems were known after the discovery of the Emerson effect. Emerson had shown that the simultaneous application of light of shorter and longer wavelengths, increases the rate of photosynthesis.