Cyclic-photophosphorylation results in the formation of

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 $+\mathbf{H}^{+}$.