Fatty Acid Oxidation Explained: Beta Oxidation Steps, Carnitine Shuttle & Energy Yield

all engineers in this video we're going to talk about fatty acid oxidation so if you guys have already watched our video

on the mobilization of fat that's going to really help you understand where we're going from here so we said in the

mobilization of uh specifically the fats where we were breaking down the triglyceride into its components

glycerol and fatty acids we were taking those fatty acids into different tissue cells what can those tissue cells be

that were taking it to again we said three really important ones were going to be heart

muscle so the heart muscle was going to be a big one so The myocardium of the heart the skeletal

muscles and even the liver okay so even the liver many many different tissues will utilize these fatty acids for

energy but the big ones are going to be your muscle and some of even the liver and you're going to see why the liver is

really important because it can generate these structures called Ketone bodies but we'll talk about

that okay so now we brought the fatty acids into this actual cell now let's just say that this is some general cell

and we're going to bring fatty acids into it all right so let's show here our fatty acids let's show these in blue

okay here's our fatty acids we bring these fatty acids from out here so again here's going to be our free fatty

acids what's going to happen is let's take for example these free fatty acids and say that they're specifically

longchain fatty acids so these are specifically longchain fatty acids so approximately about 16 carbons

long Okay so let's say we bring in a specific type of one and one of the more specific 16 carbon fatty acids is called

Palma toic acid so it's a 16 carbon chain what I'm going to do is is I'm going to zoom

on on some of those carbons I'm not going to look at all 16 carbons so what I'm going to do is I'm going to put an R

Group here and then I'm going to have a couple special carbons so let's say here is my fatty acid portion so here's my

carboxy and right next to that I'm going to have another carbon and that's going to be my Alpha carbon and then I'll have

one more carbon next to that one which is going to be my Beta carbon and then next to that I'll have many many other

carbons so in this case this would be one two three the rest of them would be how many 13 carbons long so if I wanted

to I could continue to put all the way down 13 carbon long but I'm just going to make it an R

Group now the first thing that's going to happen with these free fatty acids is we have to prevent this fatty acid from

getting out of the cell so in order to do that we're going to U utilize a special enzyme so what's going to happen

is this free fatty acid is going to be acted on by a special enzyme this enzyme is called

fatty AAL COA

synthetase and what this enzyme is going to do is is it's going to trigger the conversion of this fatty acid because

this is a fatty acid okay we need to make sure that we know that this is specifically a

fatty acid nothing on this guy but then this fat AAL COA synthetase enzyme is going to stimulate this reaction and in

order for this reaction to occur we have to utilize energy this is going to cost energy to add that COA on

so I'm going to add a CO enzyme a into this reaction but in order for me to do that it's going to cost energy what is

that in the form of ATP so I'm going to break down ATP into ADP and inorganic phosphate and by doing that I release

energy from the breaking of those bonds which adds the COA onto this fatty acid as a result then what am I going to have

over here then so now let's draw the resulting product so I'm going to have my R Group here so here's my R Group I'm

going to have my ch2 ch2 and then right next to this I'm going have my carboxy group but

specifically bound to that carboxy group is going to be a uh coenzyme a so right next to this I'm going to have a

coenzyme a right there and usually this is having some type of tho group okay now this new molecule that we just

synthesized in this first step of this reaction is called a fatty a seal COA so a

fatty a seal COA now here's the next problem so the

first thing that we had to do is we had to put a COA on this guy and let's make this a different color uh for the sake

of it let's make this one green since we had green there for COA let's stay consistent there so here's our co-enzyme

a and again it has some specialized style group on it not necessarily important in this but if you remember we

couldn't get this guy we couldn't keep it in the cell unless we put a COA on it okay well now we put a COA on it now we

got another problem we can't get this molecule into the mitochondria because of the COA now I got to do something

specific that can actually transport it in okay there's another molecule this molecule is coming from

this specific transporter this guy right here is adding on a special molecule to this guy okay what is this molecule that

he's adding on to him he's adding on a molecule which is called carnitine okay so carnitine is going to

combine with this fatty AAL COA and look what happens here so I'm going to bring this fatty ailco down through and then

what happens is this fatty ail COA is going to combine with what the carnitine when it combines with the

carnitine it gets rid of the COA so now that COA is going to be lost okay so we did that reaction just to get rid of the

COA hm that's weird we'll see why y so now we release the Coen a and we add in the carnitine as a result I'm

going to form a molecule called fatty AAL it's no longer COA it has a carnitine onto it carnitine so it's

called fatty AAL fatty AAL carnitine that fatty AAL carnitine can be transported through this structure this

transluc case and again what's going to come out on this side the molecule that we have on this side is going to be

specific spefically look I'm going to have my carbon Here and Now what's going to be bound to

it carnitine carnitine will be bound to this what is this molecule here called this molecule here is

called fatty AAL carnitine but here's the next

problem having this fatty ail carnitine it can easily go back out through that transc case because this is a

bidirectional transc case so to prevent from him from getting back out guess what I have to do I have to rip that

carnitine off and then add another co-enzyme a back onto it okay so how do I do that you see this guy right here

this enzyme this enzyme is going to take a COA so let's say he takes this COA here he takes that COA coenzyme a and he

adds that co-enzyme a onto this fatty ail carnitine so he adds this Co enzyme a onto this fatal carnitin but at the

same time he rips off that carnitine so look what he does this enzyme is going to break this Bond here and rip off that

carnitine and then he's going to add on this COA and look what we get as a result of this reaction let's do this in

pink here because this is an important step here as a result what are we going to

get then now the result is going to be again a fatty a seal group with a co-enzyme a so now let's draw that so

we're going to have our our group ch2 ch2 carbon double bond oxygen and then again it's going to be bound to a

co-enzyme a over here now let's put our a there now next thing what happens to

that carnitine that we ripped off the fat ail carnitine it's going to get pushed back out so this fatty AAL

carnitine guess what's going to happen he can get pushed back out here and recycled now the question at hand is

what the heck are these molecules that are doing this process this one right here they has two

names this one right here on the outer membrane because you know this is the mitochondrial Matrix so we call this the

mitochondrial Matrix and then out here this is the outer membrane of the mitochondria out

here is the cytool on the cytosolic side of the mitochondria you have this

transporter this transporter here is called carnitine a

seal transferase type one okay so again what is this molecule here called this molecule here is called

carnitine AAL transferase type 1 you know they also have another name for it since we're dealing with 16 carbon fatty

acids they can call it carnitine pulati specifically carnitine pulati transporter type one so you can see it

as cat one or cpt1 just in case you see it in the literature it can be references as carnitine AAL

transferase um type one or carnitine pulo transferase type one just in case you see it in different literatures and

that way right okay so what is he doing he's adding carnitine onto the fat AAL COA getting rid of the COA and then this

fat AAL carnitine structure is getting transported through this transc case into the mitochondrial Matrix once in

the mitochondrial Matrix to prevent him from getting back out he has to be acted on by this enzyme who rips the carnitine

off and pushes that carnitine back out into the the cytool Via this translocase and then he this enzyme or transporter

adds on a co-enzyme a what is this transporter called This is called carnitine acal transferase type two or

again cartine pomor transferase type two now that we've done that what have we formed we're not even close to done and

it's crazy we formed this fatty a seal COA so from this step we formed a fatty AAL

COA that now we're going to undergo this next step so what was this first step that we just performed the first step

was getting the fatty acid into the cells the next thing was activating it so this step right here is called

Activation so again what is this step right here called let's denote this this step right here holy crap this step

right here is called Activation so you're activating the fatty acid by adding a co-enzyme a and

converting ATP into ADP in our inorganic phosphate and this reaction is catalyzed by fatty COA synthetase the second step

is going to be the transport so how we're actually getting this specific fatty COA into the

mitochondria so that we can undergo this next step this next step where we'll spend most of the time is going to be

called beta oxidation okay so now we're going to

take this fatty AAL COA through a series of reactions the first thing that we're going to do

we need to denot the nomenclature of this molecule so you see this carbon right here this is our number one

carbon this is our number two carbon but sometimes we refer to the number two carbon as the alpha carbon and this is

our number three carbon but sometimes we refer to the third carbon as the beta carbon and then you'll go on and on and

on and on now here's what's going to happen in the first step of this reaction I'm going to remove a hydrogen

from this guy and a hydrogen from this guy and an extra electron what do you call that whenever you have a hydrogen a

proton plus two electrons it's called a hydride so I'm going to pull hydrides off of this molecule who's going to do

that F A so let's show this reaction here so look what's going to happen here in this step right

here I'm going to have fad come in so f a d is going to come in and pick up a hydride from this guy and a hydride from

this guy and then that's going to turn into F A dh2 what enzyme is catalyzing this step

this is a fatti a seal COA so they call this a seal COA and you know how you're having a specifically some type of

co-enzyme involved that are picking up hydrides usually that's a dehydrogen so this is an AC COA de

hydrogenase okay when this happens you're going to rip that hydrogen off that hydrogen off and you're going to

form a double bond to stabilize that molecule so now what am I going to have here I'm going to have a double bond

between my Alpha and my Beta carbon so let's show that as a result this is the first step so this is step

one then as a result I'm going to have a CH here double bond here let's make that double bond a different color so that we

very very are particular with distinguishing the difference here so now let's go ahead and put this in this

color here this is our double bond there okay okay then on the other side I'm going to have a

CH and then a carbon doubly bonded to an oxygen who's still bound to a co-enzyme a okay that was the first step not too

bad in the Second Step I'm going to do something weird I'm going to take and I'm going to add water across that

double bond but in order for me to add water across that double bond I'm going to need an enzyme who can help me do

that in other words I'm going to need an enzyme who can hydrate this so how do you do that so let's do this next step

the next step of bit oxidation step two is I'm going to hydrate this guy how am I going to do

that I'm going to add water into this reaction so I'm going to take water and I'm going to add water into

this reaction but in order for me to do that I need an enzyme who can facilitate that reaction just like AC COA

dehydrogenate stimulated this step I need an enzyme who can stimulate this step that enzyme is called

o COA hydrase now you're probably wondering

where the heck did this Eno COA come from that's what this molecule here is called this molecule is called Eno

COA so this molecule is called Eno COA but we have have to be even more specific this hydrogen here really

should be poking upwards this hydrogen here should really be poking downwards so now this double bond

is having the hydrogen's on opposite sides that's trans so technically and this is on between what this is the

first carbon this is the second carbon that's the third carbon so we denote double bonds whenever we're doing

nomenclature according to like IUPAC that that's going to be where I put my double bond I name it like that way so

they call this trans because the hydrogen's on opposite side Delta 2 to signify that there a double bond between

the second and the third carbon so they call this molecule technically trans Delta 2 in oil

COA then once we have this trans Delta 2 in oil COA what's going to happen he's going to get acted on by this Eno COA

hydrase this Eno COA hydrase is going to add water across this double bond and then you're G to have an O here and

you'll have an H there that's all that's going to happen because when you add water you add an O to one side and an H

to the other side so now let's draw the resulting molecule as a result here I'm going to

have R let's actually bring this up a little bit let's actually bring this reaction up a little bit here let's

bring this Arrow this way guys and that's a little better okay this is again the second step now we're

getting ready to enter into the third step so now we're going to have the again R Group carbon hydrogen

and then we're going to have that double bond I'll put that double bond in just a second carbon hydrogen and you're again

you have the carbonal group and again what is bound to that carbonal group co-enzyme a with a

thol what is going to happen in this step here okay so since we added the water

now what should be the result I should get rid of that double bond that double bond should go away because I added

water across it when I add water across it let's actually make this double bond like that now now let's put different

colors on this that water I'm going to add an oh to this side to the beta carbon and I'm going to

add a hydrogen to the alpha carbon so again what is this carbon right here this is

number one carbon Alpha Beta carbon because the hydroxy group is on the beta carbon of this fatty COA we

call it beta carbon so the beta carbon of the Third carbon beta hydroxy AC COA that's all you call it so it's not a

hard molecule to name right so again what do you call this molecule beta hydroxy

acal COA molecule and that is formed by this enoc

COA hydrase adding water across this double bond now we have another step we're going into the Third thir step

there's three there's four steps total and I'll give you aonic that helps you to remember it very

easily okay then in this third step of the reaction I'm going to bring in an enzyme

who's going to help to have NAD positive turn into nadh and what that's going to do is you see this o here and you see

this H here what this enzyme is going to do is it's going to do something very very cool this hydrogen right here I'm

going to circle this one he's going to take that one and he's going to take take this one that n positive so the N

positive is going to come over here let's say here we have a n a d positive he's going to get converted

into n a d h and he's going to pick up some hydrides when he picks up those hydride ions this carbon has no choice

but to form a double bond between that oxygen right there because I'm going to lose that hydrogen and that hydrogen as

a result what am I going to have then as a result let's let's draw it here this guy is going to have to have a double

bond carbon to I mean double bond oxygen we'll show that in a second this guy's still going to have his hydrogens we're

still going to have the carbonal and that carbonal is still going to be bound to a co-enzyme a with the Tho group but

what's the difference now now we're going to have a double bond between this oxygen here double bond between that

oxygen and this hydrogen is left alone what do you call this mod molecule okay well now there's a ketone because

there's a carbon here a carbon here so that's a ketone on the beta carbon because again this

is one alpha beta so if the Ketone group is on the beta carbon and this is a fatal group with a COA they would call

this beta keto AAL COA okay this molecule is called

beta keto isal Co a and the enzyme that's driving this step a very cool enzyme what did I tell

you guys if you ever see NAD going to nadh you always know that there's a dehydrogenase present so just say the

name of this molecule and then put dehydrogenase after that's it this enzyme is called

beta keto acal specifically beta keto AAL COA dehydrogenase

okay so we have a beta keto acoa dehydrogenase who is stimulating this step and doing what converting this

alcohol group this beta hydroxy a COA into a beta keto AC COA now we go into the fourth and final

step okay what's going to happen here is I'm going to take something a special enzyme this enzyme is very very

special this enzyme is called thas and what this thas enzyme is doing is it's doing two things in this

reaction okay one carbon Alpha carbon beta carbon right if I were to come over here for a second and I were to just

expand on that R Group for just a little bit I could technically draw another ch2 and another ch2 and then I'll just

put an R Group here for a second now this is one alpha beta carbon you know what I can technically call

these afterwards after what I'm going to do in this step here is I'm going to cleave

this bond between the Alpha and the beta that's my my goal in this step I'm going to break this Bond the bond between the

Alpha and the beta carbon when I break the bond between the Alpha and the beta carbon I'm going to release out what

acetyl COA but then the problem is I have this whole fatty acid group that is going to be you know what am I going to

do with him I'm gonna add in a COA so what happens in this step here is thas is going to cut this Bond

right here between the Alpha and the beta carbon and at the same time he's going to add a CO enzyme a but to who to

the beta carbon after this bond is broken so now look what two products we get out of this so I'm going to show one

product going up and one product coming over here so as a result I'm going to get two products

one product I'm going to show is going to be this side okay so now if I show this

side of that broken bond I'm going to have a r group ch2 ch2 and then this is going to be a

carbon with a double bond oxygen because all I'm going to do is just draw a double bond oxygen

there and then what did I say this thylas is adding that co-enzyme a onto the beta carbon after this bond is

broken so what am I going to see right here Co enzyme a with a th group this is a new fatty ail COA where is this fatty

ail COA gonna go guys let me show you this fatty ail COA is going to go back over here and

get recycled and it's just going to go through another round of beta oxidation now the question at hand is why do they

call a beta oxidation because what I was doing is I was breaking the bond between the Alpha and the beta carbon I'm

breaking that Bond and I'm releasing out a fatty a Seal Co so this is a regenerated fatty ail COA it's just two

carbons short so this is a fatty ail COA and all it is is just two carbons short but it'll go and get

broken down again and it'll go from 16 now it's going to be 14 so this is a 14 carbon fatty it'll go through it again

and make 12 go through it again make 10 you guys get the point What's the other product of this reaction because I said

there was two products okay the other product now I'm going to

show this side what's going to happen is this carbon is going to pick up a hydrogen

it'll pick up a hydrogen and you're going to get a ch3 group so that's going to be this carbon this is our Alpha and

then right next to it I'm going to have the carbonal group and what's bound to that carbonal group Co enzyme a with a

thy component what is this molecule here called this molecule you guys have seen many many times this is called

acetal COA you might not have seen him like this in this form but you've heard of him and he is a two carbon molecule

what can happen with this acetyl COA you guys already know what can happen he can do what he can go and enter into a

specific cycle what is that cycle guys the kreb cycle out of the kreb cycle what can I generate from the CB cycle so

from this guy right here this cetto COA what can I do with him I can bring him into the crab

cycle he can be reacted in the kreb cycle and then what happens you produce what

nadh's fadh2s and a little bit of ATP what can happen with these nadh is these fadh2s

they can take it to the electron transport chain and lead to oxidative phosphorilation to where the overall

result is going to be what ATP formation because remember what I told

you guys what was the original problem of why we were doing this whole beta oxidative process the whole reason we

were doing this beta oxidative process because our blood glucose levels in the blood were low if our blood glucose

levels are low it means we're fasting that means that we don't we're either not taking in enough carbohydrates into

our diet maybe due to doing a ketogenic diet or like some type of Atkins diet or maybe you're having uncontrolled

diabetes mtis and you haven't taken your insulin whatever it might be your body needs another fuel source so your

primary fuel source is carbohydrates but when that is not available your body reverts to the secondary fuel source

which is fats and so it starts breaking down fats to make what a cetto COA I can't stress how important this whole

process is because the whole overall result depends upon this right here that the whole significant purpose of beta

oxidation is is to produce two carbon fragments at a time which is going to be called acetylcoa now the last question

is if we take a 16 carbon fatty acid so let's say I take that 16 carbon fatty acid and I run it through

beta oxidation 16 carbon fatty acid and I run this 16 carbon fatty acid through beta

oxidation the question is how many coaz will this produce well I told you it chops it into two carbon fragments at a

time if it chops it into two carbon fragments at a time how many acet coaz am I going to produce then I can produce

up to eight acetal coaz wow and then with Ado imagine how many nadhs and fadh2s we can produce

we're going to do that in another video where we calculate the total energy yield of how much a 16 carbon fatty acid

how much ATP can actually produce it's insane now the next question is this sometimes gets people

how many rounds of beta oxidation actually occurred this is a tricky one some people will be like oh well you

make a to c to COA you start with 16 you do it eight times no it's seven rounds of beta oxidation the reason why is

think about it like this guys let's come over here for a second let's say I draw this for a

second so one two three so we got 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

if I start right here and I cut each one of these pieces here so this is we're going to call this the number one carbon

and this is going to be this 16 carbon all right and I'm chopping them into two carbon fragments so this is one and two

so I'm going to chop here then I'm going to go one two chop here one two chop here one two chop here you guys get the

point I'm going to chop here how many Cuts did I make I made one two three four five six seven cuts on this

molecule because when I cut this thing the seventh time let me actually do this one in a different color when I cut this

thing the seventh time what am I doing I'm breaking this four carbon fragment into two two carbon fragments so that's

why sometimes certain professors will say how many rounds of beta oxidation did you do for a 18 carbon fatty acid

just put the number of acetyl coas minus one that's how you figure it out so if they ask you you they say they take a 26

carbon fatty acid undergo beta oxidation how many acetyl coas will produce you just figure out okay if it's 26 I'm

going to divide that by two so I get 13 acetyl coas minus one that's going to give me 12 rounds of ba

oxidation okay guys in the next video we're going to talk about the energy yield and we're going to talk about

certain other types of fatty acids that being odd chain fatty acids and also there is another process of beta

oxidation that can occur in peroxy so in the next video we're going to talk about odd chain fatty acids being broken down

we're going to talk about the beta oxidation that can occur in peroxisomes and the energy yield that can come from

all of this oxidative process