Structurally, the difference between the acetyl-L-carnitine (ALC) and L-carnitine (LC) is that ALC is an LC molecule that also contains an attached acetic acid group. This structural difference is small, but it produces a considerable difference in the biochemical properties of the molecule and, consequently, in its effects on metabolism.
Cracking the code on aging remains one of the biggest challenges in science today. As recently as a decade ago, the general aging theory focused on the oxidative stress model. Basically, the idea was that aging is due to the sustained accumulation of cellular damage and a lifetime of reactive oxygen species and free radicals coursing through our veins.