The potato first might become skinless. Then you denature it's DNA, essential enzymes with high heat as you cook it.
Then it goes into your mouth as salivary amylase begins breaking down the starch into disacharride (2 sugar) units.
You chew and mash it up, and the bolbus travels down the esophagus into the stomach, it gets hit with acid and becomes chyme/neutralized as the Pancreas do their thing secreting maltase and sucrase to break down the two carbon sugars into glucose, which will then either be metabolized for energy/converted into fatty acids or stored in the liver as glycogen. At this point, within the body, the potato's fate is no different than an animal whose carcass has become nutrition for the earth. Anything not broken down goes back into the S.I, then water is taken out in the L.I, and then out the rectum/anus as poop/constipation because you didn't drink enough water as you ate the potato. (lol [MENTION=3998]niffer[/MENTION])
my short answer to this is that when it gets to the point where its unique chemical make up is no longer so, it is no different than other strarch-based foods to be digested.