Question

Which of the following is not related to photosynthesis in purple sulphur bacteria?
A. Requirement of a hydrogen donor
B. Requirement of light
C. Release of oxygen
D. Use of atmospheric carbon dioxide

Answer 1

Hint: The change in reducing agent can change the end product. Purple sulphur bacteria use hydrogen sulphide as a reducing agent instead of a compound that is used by normal plants for the process of oxidation and reduction.

Complete step by step answer: Purple sulphur bacteria are a type of proteobacteria that are dependent on light for the process of photosynthesis. They are phototrophic in nature. They are anaerobic organisms and are commonly found in hot springs or stagnant water bodies such as lakes and ponds. The bacterial photosynthesis is similar to the normal photosynthesis in plants. They also use hydrogen for the process of photosynthesis like plants do. But in case of bacterial photosynthesis, hydrogen sulphide acts as a hydrogen donor. They do not need water for the process of oxidation and reduction, and therefore, do not release oxygen. It is a type of chemosynthesis in which organisms use the energy released by chemical reactions to produce sugar.
Hence, the correct answer is option C.

Note: Under anaerobic conditions, purple sulphur bacteria use simple molecules such as organic acids or hydrogen sulphide as hydrogen donors. The electrons that are released from these hydrogen donors are pumped by some electron carriers. During pumping of electrons, a proton gradient has generated that helps to generate ATP by ATP synthase.