amplification of signal (biological signals)

Fire: Fire is an example of one sort of amplification. Naively amplification of heat, we give a little heat and it get's amplified. Heat is one kind of energy so it's wrong to say amplification of energy. We can think of it as one kind of signal amplification. The existence of fire indicates the existence of initial activation energy. Flammable substances are systems for amplifying a signal namely activation energy. Initial activation energy may be very low to notice but it is transformed to fire which contain large amount of things and light to be noticed.
Production of fire involves chain reaction as shown below.
















In every step the energy released is not completely used in transforming substrate to product, the extra energy is added as the reaction goes on and it gets hot and bright.

Enzymes: Enzymes transform one type of substance to other. One enzyme molecule can easily transform a large amount of substances. This is one sort of amplification.


In biological system one excited enzyme molecule can transform thousands of other molecule in small time. This way signal which excite or activate a single molecule can be amplified. Fire usually amplifies in uncontrolled way but biological signal amplification is controlled.