The body is not
different FROM any other machine.
A motorcar
engine,for example, needs fuel IN the form of petrol.
It is burnt INSIDE
the engine to produce the energy which drives the car.
But
petrol,gas,coal,wood or any other form OF fuel can only burn IN the presence of
oxygen. Thus, all machines and body cells are alike BY requiring oxygen to burn
their fuel and thereby producte the energy needed to perform their functions.
Fuel or nutrients
and oxygen are carried IN the blood to all parts of the body.