Red blood cells, renal medullar cells, and certain cells in the retina. Now do you see why it would be a problem if they stopped working during starvation? Hint: You'd die rather quickly.
Those cells are unable to use conventional oxidative metabolism like the TCA cycle, ß oxidation of fatty acids, oxidation of ketone bodies and most amino acids, and the electron transport chain are all mitochondrial pathways absent from those cells.
Ergo, they can only use glucose as a fuel and can only metabolize it as far as lactate (primarily via glycolysis and perhaps a little in the pentose phosphate pathway).
Another group of cells do have mitochondria but for some unknown reason do not oxidize fully glucose although they do show high rates of glucose to lactate metabolism. Maybe it's because they are sensitive to oxidative stress and mitochondrial oxidation is the main source of this.
These include enterocytes, colonocytes, immune cells, and some tumor cells. The important point about such metabolism is that it is probably continuous. Ie, there's little evidence of regulation, eg, a red blood cell will always need to do glycolysis. Since it ends at lactate (instead of pyruvate then into the mitochondria), the body is able to resynthesize glucose so it does not waste glucose! Where have we heard that before?!
That's all for now!
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