Photosynthesis Question 47
47. Which one occurs both during cyclic and noncyclic modes of photophosphorylation?
[1994]
(a) Involvement of both PS I and PS II
(b) Formation of ATP
(c) Release of $O_2$
(d) Formation of NADPH
Show Answer
Answer : b
Hints & Solution
(b) Cyclic photophosphorylation can be used to produce a steady supply of ATP in the presence of sunlight. However, ATP is a highly reactive molecule and hence cannot be readily stored within the cell. Non-cyclic photophosphorylation produces NADPH in addition to ATP (this requires the presence of water). In the Z-scheme, electrons are removed from water (to the left) and then donated to the lower (non-excited) oxidized form of P680. Absorption of a photon excites P680 to P680*, which “jumps” to a more actively reducing species.
