The bacteria conducting an anoxygenic photosynthesis use which of the following compounds as an electron donor?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. Hydrogen sulphide.
Bacteria that perform anoxygenic photosynthesis use compounds other than water as electron donors, because this type of photosynthesis does not produce oxygen. Common electron donors include hydrogen sulfide (H₂S), hydrogen gas (H₂), ferrous ions (Fe²⁺), and organic compounds. For example, purple sulfur bacteria and green sulfur bacteria use H₂S, producing elemental sulfur instead of oxygen.
Other options:
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Water (H₂O): Used in oxygenic photosynthesis by plants, algae, and cyanobacteria, producing oxygen.
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Carbon dioxide (CO₂): Acts as a carbon source, not an electron donor.
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Oxygen (O₂): Not used as an electron donor; it is the final product in oxygenic photosynthesis.