- Combustion is relatively fast and can be controlled only by
the amount of fuel and oxygen available. The energy products of
combustion are light and heat, which can be intense. Some of the
heat of combustion can be converted to other forms, such as mechanical
motion (as in a steam engine). Carbon dioxide is a major product
of combustion.
- Respiration is relatively slow and controlled. The energy products
of respiration include heat and the fuel for life processes, including
growth, reproduction, and movement. The heat of respiration must
be maintained within strict limits if it is not to damage the
living tissues within which it occurs. As with combustion, carbon
dioxide is a major product of respiration.
Just about any compound with carbon will combust. Complex compounds
like carbohydrates, fats, and proteins will burn, as any careless
cook knows. However, only simple carbon-containing substances can
take part in respiration. The chemical equations for combustion and
for respiration are identical.
Combustion of a carbohydrate
(CH2O) + O2 -> CO2 + H2O + Energy (Heat and Light)
Respiration of a carbohydrate
(CH2O) + O2 -> CO2 + H2O + Energy (Heat and Fuel for Life Processes.)
