Answer:
I started out as glucose, got converted to pyruvate, after which I got oxidised by Oxygen to become CO2
Step-by-step explanation:
My name is CO2, and I started out as glucose from pure honey. I got eaten by a little child when I was two weeks old, and I had to go through the dreadful process of aerobic respiration in the child's body.
My glucose molecules were broken down into pyruvate, and I stayed that way for a while, as I made my way to the mitochondria of the child's cells. Once I got to the mitochondria, I met my old friend oxygen, who reacted with me to turn me into the molecule I am today - C02.
If you want to know how I escaped the child's body, that's easy - I simply snuck out his nose while he was breathing one cold dark night.