Answer: cellular respiration reverses the overall photosynthetic reaction, but less efficiently. The useful energy output of respiration is less than the energy input required for photosynthesis.
Step-by-step explanation:
overall photosynthetic reaction
Light energy + 6CO2 + 6H2O —> C6H12O6 + 6O2
cellular respiration
C6H12O6 + 6O2 —> 6CO2 + 6H2O + energy (as ATP and heat)