Question

Halobacterium salinarium uses the following for the active transport of ions to induce purple colour.

(a) Light energy

(b) ATP

(c) Voltage

(d) Chemical energy

I had been asked this question in an interview for job.

I'm obligated to ask this question of Movement of Substances Across Cell Membranes in chapter Cellular Membranes of Cell Biology

Answer 1

Right option is (a) Light energy

To explain I would say: Halobacterium salinarium is a halophilic archaebacterium, which takes on a purple colour when grown under anaerobic conditions. This is due to the presence of bacteriorhodopsin, a proton pump which depends on light energy. The absorption of light in the retinal group of bacteriorhodopsin results in conformational change and a proton from the retinal group moves to the cell exterior.