Well, time for Wikipedia, to uncover the definition of a "trans fat." I'll try to find the time. To my mind a "trans" fat was an unsaturated fat, which was "hydrogenized" to create a "saturated" fat. So a trans fat is a saturated fat (saturated with hydrogen atoms) that was previously an unsaturated fat.
But, it really isn't the "trans fats" per se, according to Thomas Smith (healingmatters.com). THere is something he refers to as "cis." Something caused by the nickle that is used as a catalyst to create the trans fats during processing. Its been a while since I've read his web site, but he places most of the blame for the cell membrane disturbance in Type II on a residue from the manufacturing process.