BlondeCookie said:
I'm having a hard time figuring out the link between Fatty Acid Synthesis and TAG synthesis. Specifically, just wanted to know what happens to the fatty acid after it completes fatty acid synthesis.
Does it (the fatty acid made in fatty acid synthesis)...
a) get esterified to glycerol and later becomes TAG during TAG synthesis
b) is added to glycerol 3-P during TAG synthesis
c) none of the above
Please explain. I'm very confused about this problem. Thanks.
😕
In this situtation, the answer is a combination of B & C.
It's easiest to understand metabolism by thinking of the big picture (well-fed vs. starved).
Your Q is referring to an individual post-prandial, most likely on a high carb diet. Glycolysis in the
liver results in increased quantities of Acetyl-coA and Glycerol-3-P...as well as ATP and Citrate.
1)The NADH produced in glycolysis favors the conversion of DHAP --> Glycerol-3-P
2)ATP & NADH inhibit citrate synthase & Isocitrate dehydrogenase, which inhibits TCA cycle --> increased acetyl CoA --> FA synthesis
3 FA's are esterified to Glycerol-3-P --> TAG (choice B)
FA is esterified to cholesterol --> cholesterol ester (choice C)
Both are then packaged into VLDL and shipped off into the blood stream.
A very similar process occurs in the enterocyte, except the TAG and CE is packaged into chylomicrons that percolate through the lymph before reaching the thoracic duct.
Choice A would be incorrect because there isn't really a storage depot of monoacylglycerols. This would also be a highly inefficient storage form of fat as well, due to the increased need for water to hydrated the unoccupied OH groups on the glycerol molecule. 2-MAG does exist transiently in the enterocyte before it is reassembled into TAG.
I didn't include every enzyme along the pathway...if you're studying for biochem you'll need to know em, if you're studying for the step they're not HY.
