In purple and green bacteria, oxygen is not evolved during photosynthesis because hydrogen donor is

Options

(a) H₂O
(b) NH₃
(c) H₂S
(d) CH₄

Correct Answer:

H₂S

Explanation:

Purple and green bacteria are photoautotrophic bacteria which respectively have bacteriochlorophyll and bacteriophaeophytin as photosynthetic pigments. These bacteria perform anoxygenic photosynthesis i.e. no O₂ is evolved during photosynthesis because of this water is not used as a source of reducing power, instead hydreogen is obtained either directly (some purple bacteria) or from various types of inorganic and organic compounds, e.g., H₂S (green bacteria).
H₂S → 2(H) + S