Question

2. In cyclic photophosphorylation, it is estimated that two electrons must be passed through the cycle to pump enough protons to generate one ATP.

a) What is what complexes and what processes are involved in “cyclic photophosphorylation”?

b) What is the first consequence of the electrons movement?

c) Assuming that the deltaGo' (delta G naught prime) for hydrolysis of ATP under conditions existing in the chloroplast is about -50 kJ/mol, what is the corresponding per-cent efficiency of cyclic photophosphorylation, using light of 700 nm?

Answer 1

a). complexes needed during cyclic phosphorylation- complexes are protein molecules which act as electron transporter, such as - ferrodoxin, plastoquinone, cytochrome b and cytochrome f, and plastocynine. Six turn of cyclic phosphorylation is required to produce one glucose molecules because six turn of cyclic phosphorylation will produce total 12 ATP.

the process of cyclic phosphorylation includes, firstly photoexcitation of photosystem 1 , which get excited at 700nm. secondly flow of electron which is carried by electron transport chain and the electron is finally returned back to PS 1, and lastly formation of ATP molecules.

b). In cyclic phosphorylation only one antenna molecule is involve (photo system- 1), when sunlight falls on PS 1 , the electron get excited and return back to PS 1 via series of electron transport chain, such as cytochrome B & F.

c). >50%