Question

The sulfur cycle differs from the nitrogen cycle in that Choose one: A. only sulfate, and not nitrate, can be used as an electron acceptor at the end of an electron transport chain. B. only nitrogen, and not sulfur, exists in multiple oxidation states. C. only H2S, and not NH3, is a substrate for photolysis by phototrophs. D. prokaryotes play an important role in nitrogen cycling but not sulfur cycling,

Answer 1

The answer is C. The sulphur cycle differs from the nitrogen cycle in that only H2S, and not NH2 is a substrate for photolysis by phototrophs. Any organism that use the mechanism of photon capture and produce complex organic compounds for acquiring energy are called phototrophs. Phototlysis is a part of light dependent reaction of photosynthesis. The formula for photosynthetic photolysis is given below.

           H2A+ 2 photons → 2 e− + 2 H+ + A

        Here the type of organism determines the chemical nature of "A". The explanation can be further confirmed by taking organism purple sulphur bacteria as example. In this case hydrogen sulphide (H2S) is oxidized to sulphur.