In photosystem II of purple bacteria, electrons flow through cytochrome bc, coupled to pumping of protons and the proton potential drives synthesis of ATP. The cytochrome bc complex transfers the electrons back to bacteriochlorophyll P870. This type of ATP synthesis is called
A) reverse electron flow.
B) membrane potential.
C) noncyclic photophosphorylation.
D) cyclic photophosphorylation.
E) proton motive force.

Question

Quizplus · Accepted Answer

This type of ATP synthesis, where electrons flow through cytochrome bc and then back to bacteriochlorophyll P870, is characteristic of cyclic photophosphorylation. In contrast, noncyclic photophosphorylation involves the transfer of electrons from water to NADP+ through both photosystems, with the generation of a proton gradient and ATP synthesis via ATP synthase. Reverse electron flow refers to a process where electrons flow in the opposite direction of typical electron transport, often used by bacteria to generate reducing power for biosynthesis. The proton motive force is a term used to describe the electrochemical gradient generated by the transfer of protons across a membrane, which can drive ATP synthesis. While membrane potential is related to the proton motive force, it is a broader term that includes any electrical potential difference across a membrane, not just those generated by proton gradients.

In Photosystem II of Purple Bacteria, Electrons Flow Through Cytochrome