# How do chemical equations for respiration and photosynthesis compare?

Jan 18, 2017

Well, one is the reverse of the other..........

#### Explanation:

AS you know, photosynthesis is the production of simple sugars from water and carbon dioxide:

$6 C {O}_{2} \left(g\right) + 6 {H}_{2} O \left(g\right) + \Delta \rightarrow {C}_{6} {H}_{12} {O}_{6} \left(a q\right) + 6 {O}_{2} \left(g\right)$

And dioxygen is also produced as a bonus......

On the other hand, respiration involves combustion of sugars with dioxgen:

${C}_{6} {H}_{12} {O}_{6} \left(a q\right) + 6 {O}_{2} \left(g\right) \rightarrow 6 C {O}_{2} \left(g\right) + 6 {H}_{2} O \left(l\right) + \Delta$

Because the combustion reaction involves the formation of strong $C = O$ bonds, this reaction is exothermic. And fixation of carbon dioxide, where strong $C = O$ bonds are broken is endothermic. From where does the energy come? Have green plants an energy source that we cannot utilize?