November 2005 (UTC)

Fat is never converted to Glc, not at least in humans according to the textbooks.  

Let me add few things. First, Glc enters/leaves the cell through a proces called facilitated diffusion. Which means that as soon as the Glc concentration inside the cell is somehow increased, Glc will start leaving the cell - which by the way happens in hepatocytes during glycogenolysis. Second, even if there was a way to keep Glc inside the cell, say through active transport, Glc poses a danger to the cell integrity as Glc is a highly osmotically active compound. The cell solves these two issues with a single solution by synthesizing glycogen from Glc - the enormous glycogen molecules can't leave the cell, and by having osmotically inert glycogen instead of Glc, the cell avoids the osmotic shock.  13:55, 30