# of ATPs per 18-Carbon fatty acid

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Specializes in Operating Room.

I'm making a new thread for this because there are several classes that cover this.

I have to figure out the # of ATPs that are generated by the complete oxidation of an 18-carbon fatty acid.

I came up with 144 ATPs, but looking at different websites I see different amounts. I don't know where they are coming up with the extra ATPs.

I need a firm answer, with explanation if I'm not correct. Can anyone help??

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Specializes in Operating Room.

*bump*

Anyone know if this is correct???? Hello...anyone out there?????? :rolleyes:

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Specializes in Ante-Intra-Postpartum, Post Gyne.
*bump*

Anyone know if this is correct???? Hello...anyone out there?????? :rolleyes:

Awww ,man! This is summer and I just finnished chem hell!! :chuckle I'll try to find out for you. Let me us some of that stuff they call brain power. Gotta pull out the ol brain and rub all the sun tan lotion off, its been out of use for since June :chuckle

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Specializes in Operating Room.

lol.... thanks :)

Awww ,man! This is summer and I just finnished chem hell!! :chuckle I'll try to find out for you. Let me us some of that stuff they call brain power. Gotta pull out the ol brain and rub all the sun tan lotion off, its been out of use for since June :chuckle
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Specializes in Ante-Intra-Postpartum, Post Gyne.

Sorry this is so late. I spent the afternoon with my parents since my husband is out of town. (The baseball team he is coaching is on a tournament) and then right after a came home a friend came by...but here you go:

What they usually say is that we get 44 ATP for every 6 carbons

of a fatty acid, so presumably it should be 134, although it is

possible that there are a few more or fewer. Does that help?

(Remember, that for a 6 carbon sugar, the total is 36 ATP, although

they used to say 38, but anyway, fat is more efficient than sugar with

respect to ATP production.)

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OK, now I'm curious. I'm supposed to be reviewing A&P these last few weeks before school anyway, so I'm going to check this out today. I'll let you know what I come up with.

So sad what gets me excited......

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Here's what I remember..

Every 2 carbon chain from a fatty acid that goes through the TCA cycle will generate 17 ATP. 12 from the TCA cycle, and 5 from ETS (Electron transport System).

So, according to what we were taught, the answer would be 153.

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Specializes in Operating Room.

Thanks HeartsOpenWide, but now I'm really confused....lol

This is how I came up with the 144:

The 18-carbon fatty acid is fragmented into 9 2-carbons resulting in 9 AcetylCoAs.

These enter the Kreps cycle resulting in 2 ATPs per 2 AcetylCoAs. (2X4=8 ATP also 8 FADH2s)

Then it enters the ETC resulting in 34 ATPs per 2 FADH2s. (4X34=134 ATP)

134 + 8 = 144 TOTAL ATPs

Am I just completely wrong in figuring this way??

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Specializes in Ante-Intra-Postpartum, Post Gyne.
Thanks HeartsOpenWide, but now I'm really confused....lol

This is how I came up with the 144:

The 18-carbon fatty acid is fragmented into 9 2-carbons resulting in 9 AcetylCoAs.

These enter the Kreps cycle resulting in 2 ATPs per 2 AcetylCoAs. (2X4=8 ATP also 8 FADH2s)

Then it enters the ETC resulting in 34 ATPs per 2 FADH2s. (4X34=134 ATP)

134 + 8 = 144 TOTAL ATPs

Am I just completely wrong in figuring this way??

I checked with my friend that has a PHD in Microbiology, Physiology and one more that I can not remember.

How about this?:

acetyl CoA=

# of fatty acid carbons

___________________________

2

ex: a 10 carb fatty acid would produce 10/2 or 5, CoA molecules. Every trip through the fatty acid spiral porduces one NADH plus H+ molecule and one FADH2 molecule:

# of trips= molecule NADH=molecule FADH2

The number of trips equal one less than the number of acetyl CoA molec porduced (because the last trip of the spiral produces 2 molecules of acetly CoA) Thus, for a 10-carbon fatty acid above, 5 aceytyl CoA molec are produced during four trips. Also, the four trips oruduce f our NADH plus H+ molecules for each FADH2 molec. Sooooooo.... since our head is now spinning :chuckle :

(5 acetyl CoA) times 10 = 50 ATP

(4 NADH plus H+) times 2.5 = 10 ATP

(4 FADH2) times 1.5 = 6 ATP

Activation step = -2

Total ATP = 64

You can your problem by using 18 in the places I use the 10 carb fatty in my example. ( so put 9 where I had 5 acetyl CoA and so on...)

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Specializes in Operating Room.

Wow. I didn't think this would be such a confusion....so many answers!?!?!?!?!?!

Maybe it all depends on what you learn, maybe different books state different amounts??????

Thanks for everyone's help.

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LOL OMG I feel for you. My answer would have been different as well- yikes!

In fact I did it 3X and came up with 2 different answers - geez ha ha!

Good luck!

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Specializes in Operating Room.

Hopefully if that question is on the lecture test it will have values like A) 2000 B) 3 C)144 (or close to it)

LOL :)

LOL OMG I feel for you. My answer would have been different as well- yikes!

In fact I did it 3X and came up with 2 different answers - geez ha ha!

Good luck!

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