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Overview of Fatty Acid Oxidation

1D: How do we extract ATP from fat? How much ATP do we produce? Created by Jasmine Rana.
Video transcript
what I've drawn here is the chemical structure for a try Cecil with the ride and recall that this chemical structure is commonly what we are referring to when we talk about the type of fat found in our food as well as how fat is stored in our body now the question I want to begin to answer in the figures how do we extract ATP the chemical energy from this molecule because you've probably heard that fats are a very rich source of energy but how exactly do we get a TV from a structure like this well the first thing i want to point out if that ninety-five percent of the chemical energy that we can extract from this molecule comes from these carbon hydrogen rich chains that we usually refer to as fatty acid chains I'm gonna put under herbicide that ninety-five percent of our chemical energy i'll just make a symbol here of the energy that we can extract comes from these fatty acid chains of course that means the remaining five percent of chemical energy that we can extract from this molecule come from the glycerol backbone right here so this tiny portion of the model of molecules not going to really contribute a lot and you know it essentially can enter actually glycolysis potentially and where it can be oxidized further to produce a little bit of chemical energy so because these fatty acid chains are contributing to the bulk of the energy that we are extracting we're going to focus on how we extract ETP from these fatty acid chains in particular and that helped us kind of get a bird's-eye view of how we're able to extract ATP from the fatty acid chains I've actually went ahead and drawn out a 16 carbon saturated fatty acid that our body can synthesize which is called palmitic acid now if you think back to how we extracted chemical energy or ATP from glucose you might remember that we oxidized glucose we essentially stripped it of its electrons we transferred those electrons to electron carrier molecules to form reduced intermediate like nadh and fadh2 and these these carried the electrons found in that glucose to the electron transport chain where we were able to produce ATP quite efficiently ultimately we just simply want to do the same thing with our fatty acid we want to be able to oxidize it extract all of those electrons transfer them to those electron carrier molecules nadh and fadh2 to be able to be used to produce ATP in the electron transport chain and from a birth I view I think the big picture take away is to realize that what we wanted to do is essentially the reverse of fatty acid synthesis we want to be able to take this long string of carbons and hydrogen's and essentially break them down into two carbon subunits each and as we break them up into these two carbon subunits were also simultaneously oxidizing them to release all of this energy and ultimately what we're doing is we're breaking out this large fatty acid into single molecules of acetyl co a and if you remember the structure of acetyl co a look something like this so two carbons one attached to an oxygen and of course we have our coenzyme a group here which I'm abbreviating like this now notably the energy extraction process doesn't stop there remember that acetyl co a is quite a versatile metabolites when it comes to metabolism remember that this is what can enter the Krebs cycle so it can enter the Krebs cycle in the mitochondria and when enters the kreb cycle even more electron carrier molecules like any deets and fadh2 can be produced by further oxidizing this molecule and so all together you can see that the amount of ATP that's going to be produced can be enormous because we're getting electron carrier molecules both from the direct oxidation into acetyl co a as well as acetyl co is own oxidation in the kreb cycle and to give you an idea of how much ATP were really talking about I've went ahead and calculated that for each run through the kreb cycle we can produce about a net of 1080p personal co molecule and we're producing one two three four five six seven eight each of these pairs of acetyl co wait carbons and so all together we're producing about 80 ATP in the krebs cycle alone and then add that to the amount of EGP that's produced in this direct oxidation into acetyl co and that happens to be about 27 ATP and i've calculated these numbers based on counting up how many nadh and fadh2 molecules are produced at each step and then multiplying that by a conversion factor and the commonly accepted conversion factor is that they're about 2.5 ATP per molecule of nadh produced and 1.5 ATP per fadh2 but the big point that i really want to drive home here is that in the end ultimately we are producing 80 plus 27 which is a hundred and seven ATP molecules in total just from the oxidation of 116 carbon fatty acid now compare that to the amount of ATP that we produce from one molecule of glucose one molecule of glucose gives us about thirty to thirty two molecules of ATP so that's per one molecule of glucose you can see here how much more ATP that we can extract from this fatty acid