Question

Plants use two photo-systems (PSII and PSI) to conduct photosynthesis whereas both purple bacteria and green-sulfur bacteria only use one photo-system because

Group of answer choices

plants need to use photosynthesis to produce both NADPH and ATP whereas the bacteria only need to use photosynthesis to produce ATP

plants need to use photosynthesis to produce both NADPH and ATP whereas the bacteria only need to use photosynthesis to produce NADPH

Plants use visible light for photosynthesis whereas the bacteria use UV and high energy invisible light for photosynthesis

Plants are more sophisticated than the bacteria so that plants have built in redundancy in photosynthesis system.

None of the above

Answer 1

Ans : Option 1

$\odot$ Plants need to use photosynthesis to produce both NADPH and ATP whereas the bacteria only need to use photosynthesis to produce ATP.

Reason : Both green and purple sulfur bacteria perform anoxygenic photosynthesis. Non-oxygenic bacterial photosystems usually operate a cyclic electron transport (cyclic photophosphorylation) involving the photosystem and a cytochrome complex. In cyclic electron flow, a Q cycle involving plastoquinone and the cytochrome complex is thought to transport two additional protons into the lumen for each pair of electrons transported by a mechanism similar to the analogous process in oxidative phosphorylation. Thus a greater pH gradient is generated by cyclic electron flow permits the synthesis of additional ATP, but no NADPH is produced. PSII is not involved, and no O₂ evolves. During cyclic electron flow, PSI is used to generate a pH gradient and ATP. This is not the case for oxygenic photosynthesis performed by plants. They usually operate a non-cyclic electron transport (non-cyclic photophosphorylation) involving both photosystems (PS I and PS II) in series for the synthesis of ATP and NADPH.