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Post by biology_06er » Sat Oct 28, 2006 8:18 am

Hi there

Looking at a calculation in my book for efficiencies of TAG's (triacylglycerides) vs glygogen it says...

1g of glucose requires 0.033 mol of O2
and 1g of palmitic acid requires 23mol of 02

so does this mean glucose is a more efficienct fuel as it needs LESS O2 per gram?

Also another calculation which I am not sure how they got...its in regard to amount of ATP produced


monomer molecular weight=162 (just adding up atomic mass for each atom present right?)

net yeild of ATP (38+1)=39.....how did they work that out?

Same thing for Tripalmitin they said net yeild of ATP is 409 (129*3) but I don't see how they got it...I'm not really sure if we are supposed to know how to get that-or just the fact that a fatty acid yeilds more ATP?-but better to know I guess!

Thanks in advance

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Post by weesper » Sat Oct 28, 2006 2:05 pm

No it doesnt; efficiencies are usually expressed as the amounts of calories gained from burning a certain amount of x vs a certain amount of y ( be that grams or moles or whatever). Fats are more efficient in the sense that fats store more calories per whatever than sugars, this is unrelated to the amount of oxygen consumed in burning something (i.e generating ATP in oxidative phosphorylation that is of course).

Secondly, the 39ATPs are calculated from the degradtion of glucose during glycolysis during one complete cycle going through all the steps to the breakdown to pyruvate and then through the citric acid cycle. Depending on several factors in the citric acid cycle the amount can come down to 36, 38 or 39 ATPs. This might seem confusing but it all depends on whether endproducts are used in other cycles as well, if they're used for anabolism the final yield will of course be less since this consumes ATP. Just remember that breakdown of glucose through oxidative phosphoryylation yields about 36-39 ATPs, much less than just breaking down glucose to lactic acid.

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