There are no chemical or physiological differences between fruit that has ripened naturally or fruit where ethylene has been used in ripening rooms to activate the process.
Ethylene is also known as the ripening hormone.
Bananas are harvested green and transported to ripening distribution centres. Heating the air to around 16-17ºC causes the bananas to respire. The combination of warm air and the release of ethylene into the chambers starts the ripening process.
Ethylene is an odourless, colourless gas produced and released by most fresh fruits and vegetables as a natural ripening agent.
Ethylene will penetrate most substances including cardboard boxes and wood, but not a well sealed ripening room!
The conversion of starch to sugar in fruit generates heat. Controlling the heat = controlling the ripening process.
When bananas are harvested they have very high levels of starch. During ripening the starch is converted into soluble sugars, which is why bananas are so much sweeter when ripe.