The chemical 3-(3,4-dichloro-phenyl)-1,1-dimethylurea (DCMU) blocks the movement of electrons at the point indicated by the arrow in the figure below.
Which of the following would be an immediate effect of treating a chloroplast with this drug?

Question

The chemical 3-(3,4-dichloro-phenyl)-1,1-dimethylurea (DCMU) blocks the movement of electrons at the point indicated by the arrow in the figure below. 
Which of the following would be an immediate effect of treating a chloroplast with this drug?

Quizplus · Accepted Answer

DCMU blocks electron flow from photosystem II to photosystem I, preventing the establishment of a proton gradient across the thylakoid membrane. Without a proton gradient, ATP synthesis cannot occur, which would inhibit the light-dependent reactions. The other choices are not directly affected by DCMU.

The Chemical 3-(3,4-Dichloro-Phenyl)-1,1-Dimethylurea (DCMU) Blocks the Movement of Electrons at the Point