Question

Read the following four statements a, b, c and d and select the right option having both correct statements.
(a) Z- scheme of light reaction takes place in presence of PS I only.
(b) Only PS I is functional in cyclic photophosphorylation.
(c) Cyclic photophosphorylation results in the synthesis of ATP and NADPH.
(d) Stroma lamellae lack PS II as well as NADP.
A. (b) and (d)
B. (a) and (b)
C. (b) and (c)
D. (c) and (d)

Answer 1

Cyclic photophosphorylation is the photophosphorylation process that results in cyclical motion of the electrons in order to synthesize ATP molecules.

Complete answer:
The method of using light energy from photosynthesis to turn ADP into ATP is photophosphorylation. In the presence of light, the phosphate group is moved to the ADP molecules to be synthesised, energy-rich ATP. There are two distinct forms of photophosphorylation: cyclic photophosphorylation and non-cyclic photophosphorylation. In aerobic and anaerobic cases, cyclic photophosphorylation occurs. Living organisms have only two sources of energy: sunlight, and redox reactions. ATP, the universal energy currency of life, is provided by all species. In photosynthesis, photolysis or photo-dissociation of water and a steady unidirectional transfer of electrons from water to the photosystem II are generally involved. Light energy is used to generate a high energy donor and a lower-energy recipient of an electron in photophosphorylation. Electrons then spontaneously travel from the donor through an electron transmission chain to the recipient.

Photosystem I is used independently to perform cyclic photophosphorylation. This method is carried out in the membrane of stroma lamellae. There is no need for an external electron source. Oxygen is not developing because it is not compatible with water photolysis. Only ATP is produced by cyclic photophosphorylation. Cyclic photophosphorylation is not transferring electrons to NADP; instead electrons are returning to PS I. ATP formation results but no $NADPH_2$. The result is PS I only is available for stroma lamellae, but PS II and NADP reductions do not occur.

Thus, the correct answer is option A. i.e., (b) and (d).

Note: In cyclic photophosphorylation, plant cells only perform the ADP-ATP for immediate cell energy. Typically, this is achieved with a Photosystem I and Chlorophyll P700 in the thylakoid membrane. The electrons are returned from the electron acceptor to P700 during cyclic photophosphorylation, rather than going into NADP. This downward movement of electrons from the receiver to P700 allows ATP molecules to form.