Question

Why do purple sulfur bacteria need to use reverse electron transport, but green sulfur bacteria do not?

A) Purple sulfur bacteria lack photosystem I.
B) Green sulfur bacteria do not perform photosynthesis.
C) Purple sulfur bacteria use hydrogen sulfide as an electron donor.
D) Green sulfur bacteria use water as an electron donor.

Answer 1

Purple sulfur bacteria need to use reverse electron transport because they lack photosystem I and use hydrogen sulfide as an electron donor, while green sulfur bacteria have photosystem I and use water as an electron donor.

Step-by-step explanation:

Purple sulfur bacteria need to use reverse electron transport because they lack photosystem I, which is responsible for generating reducing power (NADPH) needed for carbon fixation. In contrast, green sulfur bacteria do not need reverse electron transport because they have photosystem I and can generate NADPH directly. Additionally, purple sulfur bacteria use hydrogen sulfide as an electron donor, while green sulfur bacteria use water as an electron donor.