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biochem qbank question - drgirl21
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03-24-2006, 10:28 AM
A person eats cookies made with coconut oil.The predominant fattyacid contained in it is lauric acid, which is saturated 12 carbon fatty acid.Starting with free lauric acid,what is the net energy yield in high energy phosphate bonds from each molecule of lauric acid.
a) 83 b) 93 c) 95 d) 97 e) 110
03-24-2006, 10:51 AM
C. 97
Divide the number of carbons in the FA by 2 to get the number of acetyl CoA produced...i.e 6 Acetyl CoA. Each acetly CoA gives 12 ATP... Thus 12 x 6= 72 Subtract 1 from the number of acetyl CoA produced to arrive at the numuber of NADH and FADh ... this gives 5 of each Each NADH produce 3 ATP and each FADh gives 2... i.e we get 15 and 10 ATP respectively... Then Add 72,15, 10 to get 97...
03-26-2006, 01:16 PM
Oh.. really.. how does this come up then?...The calculation I used is based on Golgian HY note... drgirl ..Does your source give explaintion for the answer?
03-26-2006, 08:07 PM
kebi, can you please explain the NADH and FADH2 part again?
Why do we substract 1 from 6(No. of acetyl coAs)?
03-26-2006, 09:30 PM
kebi herez the explanation. Its a Qbank biochem question. Even i thought the answer was 97 but after a lot of reference I accept this
 . We forget that we need 2 ATP to activate a Fatty acid.Lauric acid... 12 carbon fatty acid. IT undergoes B oxidation 5 times to produce 6 Acetyl coA To activate Fattyacid to Fattyacyl coA 2 atp are needed. ( - 2ATP) For 1 B oxidation 1 FADH( 2 ATP) 1 NADH2 ( 3ATP) are produced.So for 5 B oxidations 5*5=25 ATP are produced For 1 AcetylcoA in TCA cycle 12 ATP are produced.3NaDH2(9 ATP), 1 FADH ( 2 ATP),1 GTP so for 6 Aceylcoa 6*12= 72 ATP are produced So in total 25+ 72 -2 = 95 ATP.
03-27-2006, 04:20 AM
thanks for good explanation. but dont you feel this is too complecated to do in 1 min in the real exam?
03-27-2006, 06:17 AM
friends, this is my quick self made short cut to solve it and any related questionn in less than 20 secs.....
my formular is... n carbon=(nx12coA)+(nx5Fatty acids)-2(atp). note: n carbon is for any no of carbon given and the first n is half of the given carbon while you subtract 1 from the last n . so using this...12carbon=(6x12)+(5x5)-2 =72+25-2=95atp. so for 14 carbon=(7x12)+(6x5)-2atp =84+30-2=112atp. I HOPE IT MAKES IT EASIER.
03-27-2006, 07:40 AM
tanother way to do is know this formula..
For Even chain FA ATP=(8.5xC)-7 For Odd Chain FA ATP=8.5(C-3)+3 C=carbon |
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