Botany - Respiration in Plants Question with Solution | TestHub

Cyclic-photophosphorylation involves only pigment system-I. When the photons activate PS-I, a pair of electrons are raised to a higher energy level. They are captured by primary acceptor, which passes them on to ferredoxin, plastoquinone, cytochrome complex, plastocyanin and finallyback to reaction centre of PS-I, ie, ${\mathbf{P}}_{700}$. At each step of electron transfer, the electrons lose potential energy. Their trip down hill is caused by the transport chain to pump ${\mathrm{H}}^{+}$across the thylakoid membrane. The proton gradient thus established is responsible for forming ATP (2 molecules). No reduction of NADP to NADPH $+{\mathbf{H}}^{+}$.