Login

Join for Free!
114064 members


Fatty acid Oxidation-ATP yeild

Discussion of all aspects of biological molecules, biochemical processes and laboratory procedures in the field.

Moderator: BioTeam

Fatty acid Oxidation-ATP yeild

Postby biology_06er » Sun Oct 22, 2006 10:29 am

Hi there

Can someone please explain something...you know when you calculate ATP yeild from fatty acid oxdn well say palmitic acid C16

so it is cleaved into 8 acetyl CoA i get that part-what I don't get it says (8x12) ATP produced from TCA cycle and (7x2) from FADH2 and (7x3) from NADH. BUT how is the 12 produced from the TCA cycle-from the FADH2 and NADH right?....so why have they included it twice?

Im confused -please help
biology_06er
biology_06er
Coral
Coral
 
Posts: 259
Joined: Tue Mar 21, 2006 9:33 am

Postby MrMistery » Sun Oct 22, 2006 3:59 pm

Ok, so it's very simple actually. the fatty acid is cut into groups of 2 carbons that are used to make acetyl~CoA. The process itself occurs in four steps. but that doesn't matter. all you should remember is that in the process of forming each acetyl~CoA molecule from your fatty acid, aside from the acetyl-CoA molecule itself, a molecule of FADH2 and a molecule of NADH are also produced. the the acety-CoA is run through the Krebs cycle and produces an extra one ATP directly, 3 NADH and a FADH2

So for each 2 carbons of your fatty acid you get
1 FADH2(directly)
1 NADH(directly)
1 acetyl-CoA which in turn makes
-3 NADH
-1 FADH2
-1 ATP

Considering 3 ATP/NADH and 2 ATP/FADH2 you get
2+3+(3*3)+2+1= 17 ATP molecules.
And since you took palmitic acid as an example, to find out the total ATP yield for your molecule, multiply that by 8(everything happens 8 times) and you get 136 ATP/molecule of palmitic acid.

Out
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
User avatar
MrMistery
Inland Taipan
Inland Taipan
 
Posts: 6832
Joined: Thu Mar 03, 2005 10:18 pm
Location: Romania(small and unimportant country)

Postby biology_06er » Mon Oct 23, 2006 6:31 am

Hey there

Thanks for the explanation-helped heaps

biology_06er
biology_06er
Coral
Coral
 
Posts: 259
Joined: Tue Mar 21, 2006 9:33 am


Postby sdekivit » Mon Oct 23, 2006 3:24 pm

MrMistery wrote:And since you took palmitic acid as an example, to find out the total ATP yield for your molecule, multiply that by 8(everything happens 8 times) and you get 136 ATP/molecule of palmitic acid.

Out


Not out, because it's wrong :!:

--> everything is fine until this step. Foolow the B-oxidation: every time 2 C's are cleaved to form acetyl-CoA.

Now you make THE mistake almost every students make when studying fatty acid metabolism: the last step produces 2 acetyl-CoA and thus oxidation of C16 takes place in 7 steps, not 8:

C16 --> C14 + CoA --> C12 + CoA --> C10 + CoA --> C8 + CoA --> C6 + CoA --> C4 + CoA --> 2 CoA: 7 steps B-oxidation, not 8.

Thus the nett ATP-yield of C16 is:

7 * 4 ATP = 28 ATP (FADH2 + NADH produced in B-oxidation)

10 * 8 ATP = 80 ATP (1 CoA yields 10 ATP in Krebs cycle and 8 CoA's are formed

Then you also forget the activation step.

activation = 2 ATP (formation of palmitoyl-CoA needs 2 ATP)

--> yield = 106 ATP
sdekivit
King Cobra
King Cobra
 
Posts: 586
Joined: Sat Jul 30, 2005 7:16 pm
Location: holland

Postby biology_06er » Tue Oct 24, 2006 1:23 am

isn't it 12ATP's in the krebs cycle?

Also why do you do 4*7=28ATP are you just using 2atp/fadh2 and 2atp/nadh? cos my books is 2 and 3 respectively...not think it really matters anyhow...

anyway taking the activation step into consideration and also the values from my book I get a yield of 129ATP which is quite a big difference to 136 or 106
biology_06er
Coral
Coral
 
Posts: 259
Joined: Tue Mar 21, 2006 9:33 am

Postby kiekyon » Tue Oct 24, 2006 5:21 am

biology_06er wrote:isn't it 12ATP's in the krebs cycle?

Also why do you do 4*7=28ATP are you just using 2atp/fadh2 and 2atp/nadh? cos my books is 2 and 3 respectively...not think it really matters anyhow...

anyway taking the activation step into consideration and also the values from my book I get a yield of 129ATP which is quite a big difference to 136 or 106


some book use 2.5 ATP/NADH and 1.5 ATP/FADH2.
So, 2.5 +1.5 = 4
In your case, they simply round it up to 3 and 2 ATP respectively.
Krebs cycle produce 3 NADH, 1 FADH2 and 1 ATP
Depending on which figure you use, you can get 12(3*3+1*2+1) or 10(3*2.5+1*1.5+1) ATP per cycle
kiekyon
Coral
Coral
 
Posts: 410
Joined: Thu Feb 16, 2006 6:10 am
Location: Malaysia

Postby sdekivit » Tue Oct 24, 2006 8:16 am

kiekyon wrote:some book use 2.5 ATP/NADH and 1.5 ATP/FADH2.


most biochemistry books use 2.5 ATP/NADH and 1.5 ATP/FADH2
sdekivit
King Cobra
King Cobra
 
Posts: 586
Joined: Sat Jul 30, 2005 7:16 pm
Location: holland

Postby mariaijaz » Tue Jan 01, 2013 10:10 am

Fatty acids are both oxidized to acetyl-CoA and synthesized from acetyl-CoA. Although the staring material of one process is identical to the product of the other, fatty acid oxidation is not the simple reverse of fatty acid biosynthesis. It is an entirely different process taking place in separate compartment of the cell. This allows each process to be individually controlled.

Regards
Maria
mariaijaz
Garter
Garter
 
Posts: 2
Joined: Mon Dec 31, 2012 11:28 am


Return to Molecular Biology

Who is online

Users browsing this forum: No registered users and 4 guests

cron