Question

Light reaction is called the Z scheme because
a. It links the two photosystems in a way that resembles the letter z
b. All members are placed according to redox potential value
c. Splitting of H$_2$O takes place here
d. PS II take participate first than PS

Answer 1

Hint: In plants, photosynthesis occurs in presence of sunlight and water, and during photosynthesis, light-dependent reactions take place on the surface of the membrane, whereas inside the membrane called the lumen, and the surrounding called stroma, in those areas, a light independent reaction takes place.

Complete answer:
- For the light-dependent reactions to take place, it has 4 complexes, they are Photosystem I, Photosystem II, and Cytochrome b56, and ATP Synthase, and all these together creates the production of ATP and NADH.
- In the light reaction, the chlorophyll absorbs the photos of the light, where this light energy is converted to chemical energy, in the form of ATP and NADPH.
- This light energy is utilized in both of the photosystems such as I and II in the thylakoid membrane of the chloroplast.
- The energy splits the water and extracts the electrons from it, these electrons are formed in the photosystem II move from that system to cytochrome b6 and to Photosystem I.
- This whole process of electrons or energy transfers from one photosystem to another photosystem in the form Z symbol. It links the two photosystems in form Z.

Hence, the correct answer is option (A).

Note: In the cyclic photophosphorylation, cytochrome b6 utilizes energy from both photosystems I and II, but in the noncyclic photophosphorylation, cytochrome b6 utilize the energy from the photosystem I only to form the energy products and the oxygen as a byproduct.