Question

In context of photosynthesis, which one of the following statements is true?

• A. Photo-ionization takes place only PSI
• B. Cyclic photophosphorylation involves both PS I and PS II
• C. Photolysis of water takes place during PS I
• D. PS II preceeds PS I

Answer 1

The correct option is D PS II preceeds PS I

Photosynthesis is the process of preparing food in the presence of sunlight and chlorophyll. Photosynthesis can be divided into two stages: Light reaction and Dark reaction.

Light reaction is a light-dependent reaction and it is needed to produce energy rich molecules like ATP and NADPH by photophosphorylation.

Cyclic photophosphorylation involves only PS I and non cyclic photophosphorylation involves PS1 and PS II. In PS I, reaction centre is made up of P700​, whereas in PS lI, the reaction centre is made up of P680.

​Photolysis of water involves only PS II, in which water molecules are breakdown into hydrogen and oxygen.

Photosystem II precedes photosystem I in the electron flow of photophosphorylation.