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One of my bio textbooks has told me a few intriguing tidbits:
1) Cells get an enormous amount of energy from metabolizing glucose. One molecule of glucose can allow a cell to produce something like 36 molecules of ATP. (That counts glycolysis, the Krebs cycle, and all the chemiosmosis stuff in the mitochondrial membrane.)
2) If we have an excess of glucose we can make fat and store it, but we cannot then make glucose from fatty acids. (We can, though, make acetyl CoA, and I presume that gets dumped right back into the Krebs cycle as if it came from glucose.)
3) "If our main fuel reservoir had to be carried as glycogen instead of fat, body weight would need to be increased by an average of about sixty pounds." Whoa.
I'm starting to realize how efficient fat is. The fatty acid oxidation process is WAY EFFING POWERFUL. Every turn of the crank gets me an acetyl CoA (plus a couple of bonus bits for the electron transport chain), and there are LOTS of turns of the crank for each of those long carbon chains in one fatty acid tail. Coooooooool.
But I'm still weirded out that we can't digest cellulose. HELLO! STARCH! Er, polysaccharide anyway! Full of tasty powerful lovely GLUCOSE! Except it's chained at the wrong corner of the glucose's carbon ring, and *poof*, we can't do squat with it. Cells are weird.
Oh, an interesting dietary carb note: there are glycogens in meat. After all, that's where we store a bunch of 'em: muscle tissue. We hydrolyze those just fine if we eat meat. I wouldn't have thought of that before. Now I get to try to figure out why there's less protein in your average plant cell. Eukaryotic cells friggin' RUN on proteins. I know there's some in there.
1) Cells get an enormous amount of energy from metabolizing glucose. One molecule of glucose can allow a cell to produce something like 36 molecules of ATP. (That counts glycolysis, the Krebs cycle, and all the chemiosmosis stuff in the mitochondrial membrane.)
2) If we have an excess of glucose we can make fat and store it, but we cannot then make glucose from fatty acids. (We can, though, make acetyl CoA, and I presume that gets dumped right back into the Krebs cycle as if it came from glucose.)
3) "If our main fuel reservoir had to be carried as glycogen instead of fat, body weight would need to be increased by an average of about sixty pounds." Whoa.
I'm starting to realize how efficient fat is. The fatty acid oxidation process is WAY EFFING POWERFUL. Every turn of the crank gets me an acetyl CoA (plus a couple of bonus bits for the electron transport chain), and there are LOTS of turns of the crank for each of those long carbon chains in one fatty acid tail. Coooooooool.
But I'm still weirded out that we can't digest cellulose. HELLO! STARCH! Er, polysaccharide anyway! Full of tasty powerful lovely GLUCOSE! Except it's chained at the wrong corner of the glucose's carbon ring, and *poof*, we can't do squat with it. Cells are weird.
Oh, an interesting dietary carb note: there are glycogens in meat. After all, that's where we store a bunch of 'em: muscle tissue. We hydrolyze those just fine if we eat meat. I wouldn't have thought of that before. Now I get to try to figure out why there's less protein in your average plant cell. Eukaryotic cells friggin' RUN on proteins. I know there's some in there.
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But cows can, because they have bacteria in their stomachs which can. Is that interesting or what? Bacteria can do all sorts of odd stuff that multicellular critters can't. The diversity of where they can live, how they can live, and on what they can live is really neat.
For bonus fun, check -this- out. You are entirely correct about if a critter metabolizes glucose completely, the critter gets a whopping 36 ATPs out of one molecule of glucose. This is a pretty good yield. But, the Krebs cycle requires oxygen to run as a pathway. So, if you were an anaerobic bacterium (which I'm glad you are not!) you can't access the Krebs cycle because of lack of access to oxygen. You could only do glycolysis, which gives you a teensy amount of ATP compared to glycolysis AND the Krebs cycle. And this is why anaerobes tend to grow so slowly, i.e., have such long ass doubling times.
It's not very often that molecular observations actually nicely line up with a measurable macro level phenomenon, but when they do I love it and I love to share it!
Have fun.
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I admit I have to wonder: if I ate the kind of bacteria cows carry, would I a) get sick, b) never notice - just metabolize them like food, c) start a colony in my stomach and be able to digest cellulose? I'm guessing b, with nothing more to base my guess on than that the human stomach is a nasty place.
Speaking of aerobic and anaerobic pathways, I think yeasts are the coolest things ever because they swing both ways. I may have to try my hand at making wine or mead just because yeasts are so nifty.
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