Well, it's got to be done. You can't ignore fatty acid oxidation. It may not be as ancient a pathway as glycolysis, but its where most of the living get there energy. (Especially these days, let's just say, obesity isn't the problem it used to be...)
So, just a quick recap, for those of us who have forgotten what fatty acid oxidation is all about. Which is fair enough I guess, learning how to hotwire cars, pick locks and shoot, doesn't leave much time to revise biochemistry!
Fatty acid oxidation, the pathway which allows us to use fats as fuel, takes place in the mitochondrial matrix, produces shed loads of acetyl CoA, reduced coenzymes, and not much else. The key thing is that, in order to generate any ATP at all, you need oxygen for the electron transport chain and the citric acid cycle. We'll come to these later, if I survive. If I can be bothered.
So, if zombies don't have functioning circulatory systems, can they be carrying out oxidative metabolism? My honest answer - I haven't a clue.
Arguments in favour:
It's hard to believe that they could manage without fat oxidation. Protein reserves and glycogen can only take you so far. In addition, with their diet of mostly entrails, they are eating a lot of fat. And I don't recall seeing any fat zombies, do you? So they must be using it, don't you think?
Arguments against:
But how could they do it without a circulatory system? It just isn't possible to oxidize fats without oxygen? Although its true that they eat a lot of fat, they might use it for something else - the black, viscous fluid that they seem to be full of perhaps?
Theory:
Now this is just completely off the wall thinking, but what if that 'black gunk' is like, concentrated haemoglobin or something? What if the integrity of their tissues is so weak that oxygen just diffuses right through them? I think they can use oxidative metabolism, because they just don't have enough carbohydrates to do without it. And where the tissues are more intact, glycolysis can suffice. Perhaps this is why they rot - to increase aeration in the tissues? Our initial hopes were that they would eventually rot away, but they only decomposed to a certain point, and since then, they haven't changed much. So my theory is that the decomposition only occurred until the damage to the tissues sufficiently increased oxygenation, so that sufficient amounts of oxidative metabolism could occur. I also believe that the dark viscous fluid somehow sustains their metabolism. Perhaps testing their respiratory quotient isn't such a bad idea...
