Efficiency of energy use in photosynthesis is approximately

Question

The efficiency of energy use in photosynthesis is approximately

a) 0.99

b) 0.65

c) 0.3

d) 0.02

Answer 1

Chlorophyll's structure is such that it absorbs light primarily in the 400-700 nm region of the radiation spectrum, called Photosynthetically Active Radiation, which contains 50percent of the energy in solar photons. The plant itself only physically absorbs 80percent of incident photons in the 400-700 nm range, with the rest lost to reflection, transmission, and absorption by other molecules. Of this 40percent of the total incident solar energy which makes it to the chlorophyll antenna system, only 28 percent is converted to carbohydrates, the rest are lost in electron transfer and chemical steps. Thus, the maximum possible conversion efficiency from sunlight to carbohydrates is 50percent * 80percent * 28percent = 11percent. Land-based plants uses 40percent of the energy for its own metabolic needs, leaving 11percent * 60percent = 6.7percent as the portion of incoming sunlight which is stored as photosynthetic energy.

6.7 percent = 0.067