Question

The wavelength of blue light is about 470 nm and for red light is about 700 nm. About 7 kcal/mol is released when ATP is hydrolyzed into ADP and inorganic phosphate (under standard state conditions). Compare the energy of the photons absorbed by plants to the energy of ATP hydrolysis.

Answer 1

We know that there is an energy () equivalent associated to wavelength () which is expressed as

  

here, h = Planck's constant and c = speed of light. So, when a light of particular wavelength is incident the corresponding energy will be absorbed. The above relation also suggests that higher the wavelength lower will be the energy.

For blue light, the wavenght = 470 nm = 60.83 Kcal/mol

and for red light, the wavelength = 700 nm = 40.84 Kcal/mol

Given that the energy of ATP hydrolysis = 7 Kcal/mol

which is far less than that of the energy absorbed by blue/red light.