Metabolism | The Krebs Cycle

All right, ninja nerds. In this video, we're going to talk about the KB cycle. So, you can also call it, you know, the triricaroxyic acid cycle.

You can call it the citric acid cycle. So, there is other names for it. It was actually founded and developed by the guy named Hans Krebs.

That's that's where it came from. Okay. So, now when we go through the Kreb cycle, we've already gone over in great detail.

But we've already gone over the glycolysis pathway. We have actually gone over all the glut transporters. We've gone over the glycolysis pathway of converting what is this molecule right here.

This is glucose right here. We've converted glucose into pyuvate. And how many pyuvates have we actually made?

Technically, we made two of these, right? Because we split this sixcarbon fragment into two threecarbon fragments. So, we've actually made two pyuvates.

And during that process, you guys already know that we generated two NADHs and two net ATP. And then you know that we've already gone into detail. Whenever there's oxygen present, we can take this pyuvate, bring it into the mitochondria, and we can transition it, right?

We can get ready to transition to the KB cycle. And in that transition step or that preparation step, what did we do? We added a co-enzyme A into this reaction, right?

And then what else did we do? We generated two NADH's and we produced two CO2s by decarboxilation and that was done through this whole pyuvate dehydrogenase complex with the E1, E2 and E3. We already gone we already went over that in great detail and all the mechanisms.

Now we're going into this next thing which is the KB cycle. So we formed acceto COA from the transition step, right? This molecule here is our acetal COA.

Now what we're going to do is we're going to convert this acetto COA. We're going to fuse it with this fourcarbon fragment right here. This fourcarbon fragment is actually referred to as oxaloacetate.

So again, this guy right here is called I'm going to denote it. I'm going to abbreviate it O A. Oxalloacetate is going to combine with the acetto COA.

When these two substrates combine, they fuse together and the presence of this enzyme and we'll talk about this enzyme in a second. But OA is a fourcarbon structure combining with a twocarbon structure. And again, what is this this red structure coming off of the acettoa?

That's the co-enzyme A. When this acetal COA and when this OA combine with this enzyme, they form a sixcarbon molecule. Look 1 2 3 four five six.

What is this molecule called? This is called citrate. You know what's really interesting?

You know citrate is Krebs starting substrate for making oxaloacetate. What did I just do? I gave you guys a little quick pneummonic to be able to remember all of this.

So, it's an easier one to be able to do. Okay. So, how do I remember?

I again oxalo acidate and acceto come together in the presence of this enzyme to form citrate. And then I like to remember this citrate is Kreb's starting substrate for making oxaloacetate. Well, what is is for?

Is is for iso citrate. So, let's get all these intermediates out of the way. It's an easy way to be able to remember them because that's what we long for.

All right. Sometimes they just get it out of the way, the memorization, right? Krebs is for alpha keto gluterate.

I might refer to it as a kg whenever you guys see it like that. Starting is for sueninal COA. Suinal COA.

Substrate is for suxenate. This is suxenate. Four is fumemerate.

And then the last one is making which is going to be malate. And the last one is oxaloacetate. So again it goes citrate is Kreb's starting substrate for making oxaloacetate.

Just a little quick pneummonic. I thought that would help out to just memorize, you know, the basic intermediates. Now that we've done that, really there's nothing crazy else that we have to know other than just the regulatory steps and what's happening in between.

Okay, cool. So, let's do that. Now that we know the intermediates, let's focus on the enzymes and what's produced and what's happening in each step.

So, acetto coa and OA or oxaloacetate. When these two are fusing, there's a special enzyme. And what is this enzyme doing?

It's forming citrate. It's synthesizing citrate. So, what would that enzyme be called?

you call it citrate synthes. So there's a citrate synthes enzyme. This citrate synthes what is he doing?

He's taking the oxaloacetate in one part, taking the acetto clay in the other part, fusing them together and making citrate. Now the question is this enzyme is extremely very highly regulated. So it's going to control this step.

So acetylco going into citrate with oxaloacetate. This is not a reversible step. This is a one-way reaction.

So what does citrate synthes have to be regulated by? Okay, it's going to go on and on what you guys are going to see throughout a series of these biochem videos. Think about this.

If our body is having a lot of metabolism, so it's occurring a lot, a lot of metabolism, a lot of KB cycle, a lot of electron transport chain activity. I'm making a lot of ATP. If I'm making a lot of ATP, do you think I'm gonna want to keep having the KB cycle going on making more NADHs and FADH2s?

No. Because I already have too much of it. This is going to inhibit it.

That's going to aloststerically inhibit this enzyme. Same thing in the KB cycle. You'll see that will generate a lot of what's called NADH that you see here.

NADHs, if there's too many of them, it's also basically telling this enzyme, there's a lot of energy supply within the cell. We don't need anymore. shut down.

Don't do this anymore. Okay. Then we have another one.

Citrate himself. You know, whenever there's actually too much citrate, citrate can actually come back and inhibit this enzyme. So, citrate himself can come back and inhibit this enzyme.

So, citrate can say, "Okay, there's way too much of me. " Because generally, what's going to happen when you make citrate? It'll automatically get converted into isocitrate.

Generally, some of this citrate can also get converted into the basic units for fatty acids called malano qua and we'll see that. But generally, it should be progressing somewhere. It shouldn't be building up.

When it's building up, it's letting the citrate synthes know, don't make any more of me. Stop working. And then there's another one.

He's all the way down there though. It's called suinal COA. So suinal COA is also an alossteric inhibitor.

He's just a little bit more downstream and he's just telling this enzyme, hey, before you even think about making citrate, there's already too much of me. So, shut down and stop making more citrate and making more of me, making more NADHs, more ATP. Just stop doing that.

And these are generally the main aloststeric regulators of this citrate synthes. Now, what would be a stimulator? We've already talked about this so many times, but it's a good good way to keep continuously reviewing.

ATP gets broken down into what, guys? it gets broken down into ADP and inorganic phosphate. If you're breaking down a lot of ATP, you're going to build up a lot of ADP.

And this is going to signify that you are actually not having a lot of ATP within the cell. If there's not a lot of ATP in the cell, that's not good because ATP is needed for transport mechanisms, for metabolic pathways, for DNA synthesis, so many different things, ion channels. So ADP would be a very powerful alossteric stimulator of this enzyme.

It would let this enzyme know, hey, there's not a lot of ATP. You need to continue to keep going through the KB cycle making more NADHs and FADH2s and make more ATP. So that would be that guy.

So generally this is how we're going to aloststerically regulate this googlyide enzyme. Okay? Because this googlyide enzyme is involved in this step right here, converting the acetto into citrate.

very very highly regulated step. Okay, so we're done with that one. Okay, so now we got this Betty White enzyme.

Okay, this Betty White enzyme with the perm going on is converting citrate, which is a sixcarbon molecule into what? Okay, one, two, three, four, five, six. It's still six carbons.

So what's really happening? It's just an isomerization reaction. In isomerization reactions, all you're doing is you're just shuffling around the hydrogen's and the carbons, but there should still be the same number of carbons and hydrogen's and oxygen in this guy as there is carbons, hydrogen's, and oxygen in this guy.

So, it's just shuffling things around. Not a crazy crucial step, but the enzyme controlling this step, as you guys can see, is doing what? It's able to move in the reverse direction.

So, whenever there is too much isoccitrate, you can convert it back into citrate. It is possible and it actually does happen and you'll see this whenever we talk about this in fatty acid synthesis but the enzyme that's controlling this is called aonotase ac okay aonotase enzyme. So there is you know just because it's not controlling it's not highly regulated and is reversible doesn't mean that this enzyme isn't important.

You know, there's a rat poison. Um, in rat poison, there's a chemical that's present called fluo acetate. And what happens with this fluo acetate is it's kind of acting like acceto.

You know, acetate is just basically another fancy word for saying it's a twocarbon structure. All it has is just a florine attached to it. So, it's going to get actually converted.

It's going to act like fluoroacetate. So you know how you're going to have acetto coa here you're going to have this fuo acetto coa which gets converted into fuo citrate and that fuocitrate binds onto the aonotase enzyme and what is it eventually going to do it's going to inhibit this enzyme and this enzyme once it's inhibited it can't convert citrate and isoccitrate so you can't you won't be able to generate eventually NADHs FADH2s and ATP and that is a very very bad thing so fluoroacetate can actually cause inhibition of this aonotase enzyme and again it's within rat poison so if you you somehow terribly take on too much rat poison for whatever reason, uh, it can inhibit this enzyme. All right, cool.

Now we come into this next one. So, we're going to convert isoccitrate into alpha ketoglutarate. All right, cool.

How many carbons is this guy? Six carbons. How many is this guy?

One, two, three, four, five. Okay, cool. Five carbons.

That means I lost a carbon somewhere. Whenever you guys hear that, whenever you see a carbon missing, automatically assume that you lost that carbon in the form of CO2. What is that called?

I know we've talked about it, but what is it called whenever you lose a carbon in the form of CO2? What do they call that? They call it d caroxilation.

Okay, so decarboxilation is the the actual reaction in which you're removing a carbon in the form of CO2 primarily a caroxil carbon. Well, we're losing that. Okay.

Now, in this reaction, we have a very very important enzyme. This enzyme is called iso citrate de hydrogenase. Right away bells should start ringing in your head once you hear dehydrogenase automatically know that you are going to be converting NAD positives into NADH's okay automatically once you guys see that automatically think oh I'm going to make NADH's in this step so what happens in this reaction NA positive is reacting in the step to generate Na DH okay that's what's happening in this step.

I'm taking NAD positive and converting it into NADH. Cool. Now, you see how this step is one direction.

It's not birectional. So, this is not a reversible enzyme. It can only be moving in one direction.

Usually, any enzyme that forms CO2 is generally usually irreversible. Isoccitrate dehydrogenase has three pockets on it. Look, it's got this pocket, this pocket, this pocket.

What is going to happen here? Okay. Again, realize that whenever we're actually having high amounts of ATP, you guys can automatically think that whenever there's high amounts of ATP, this little Snoopy dog has three binding sites.

Okay, three binding sites. What's going to happen to this little Snoopy dog or the isoccitrate dehydrogenous enzyme? If there's too much ATP, ATP will inhibit this enzyme.

And that should already make sense because there's too much energy production. We want to slow it down. Whereas, think about the opposite effect.

If I'm breaking down a lot of AD ATP and generating a lot of ADP, that should stimulate this enzyme. And that it does, my friends. Okay.

And for the last one, this one's kind of going to be like, what the heck? Where'd that come from? Calcium is another strong stimulator of this enzyme.

And this should actually make sense. Think about this in the muscles. In muscles, calcium is acting as a nice important type of signaling molecule to activate the the crossbridge formation within the skeletal muscles or even cardiac muscle, right?

He's important for that because we need calcium in order for our muscles to contract. But another thing that we need for our muscles to contract is ATP. If this enzyme is stimulated, he's going to help to generate NADH's, which will take those hydrides to the electron transport chain and generate ATP.

So calcium is helping to stimulate this enzyme till we can make more ATP so we can have more contractions because he knows ATP is needed to detach the meosin from the actin for the crossbridge formation right so calcium is kind of letting this enzyme know make more ATP we're not we don't have enough ATP in the cell we need to make more ATP is an inhibitor because it's saying we have too much stop making more simple nothing crazy about that okay now we're going to move on to this next enzyme this next enzyme is extreme extremely important. We really need to remember this enzyme. This enzyme right here, look at this.

She's got, you know, locks here. This is called alpha. I'm going to do that.

Ketoglutarate KG D hydrogenase enzyme. This is an extremely extremely crucial enzyme. Okay, count how many carbons we have again.

One, two, three, four, five. For alpha ketoglutarate for sueno COA, how many do I have? One, two, three, four.

Okay, that means I must have lost the carbon. Oh, yeah. Cool.

So, there must have been decarboxilation. I must have lost a carbon in the form of CO2. So, there must have been another decarboxilation reaction.

Oh, wait. Zach said whenever I have a dehydrogen, automatically think NAD positive to NADH. Okay, so that's not bad.

This reaction is kaput. It's done. That's it.

It's not that bad because all you got to remember is okay five to four loss of CO2 decarboxilation NAD positive to NADH because there's a dehydrogenase enzyme. That's it. Now we have to remember look this she's got three pockets here in her dreads.

Okay, what's going to happen? Same thing. Now think about this one.

It's going to be a little tricky. Nothing crazy. You see soxenyl coa?

He's just sitting here. He's going to tell this enzyme if there's too much of him and if this enzyme needs to stop. So look, look what suininal COA can come over here and do.

It can come and bind onto this enzyme and it will inhibit this enzyme and tell this enzyme don't keep converting alpha ketoglutate to suininal COA. We don't need to do that anymore. There's either too much ATP, there's too much NADH, there's too much energy produced in the cell.

Stop. Okay. Now the next ones are the next one's a little weird, but it's not crazy.

You see these NADH's if you start generating too much NADH's that can also tell this enzyme to shut down. So this NADH can actually come over here. And what can it do?

Look, here's our NADH. If there's too much NADH's, what will it do to this enzyme? It will inhibit this enzyme.

Tell this enzyme, don't keep converting me alpha ketoglutate into sueninoquake because there's already too much NADHs. We need to stop making as much and that will inhibit this enzyme. And the last thing is super simple because we already talked about him calcium, right?

Calcium is also going to work in this step too. So you're going to have NADH who's going to be inhibiting this enzyme. Sucks in a COA which is going to be inhibiting this enzyme.

And then what else is going to be working in this step? Calcium. Calcium is going to be doing what in this step?

calcium is going to be stimulating this enzyme here. Okay, so now that should make sense now, right? Because we we generated CO2 by decarboxilation.

We generated uh some NADH's out of this reaction because we had the alpha ketoglut dehydrogenase. But then we need to be able to regulate this enzyme to control how much activity is going on. If there's too much succininoa from too much KB cycle activity, it's going to inhibit this enzyme to stop this this KB cycle from continuing to occur.

If there's too much NADHs that are being generated, it'll also inhibit this enzyme, tell it not to continue to occur because we already have too much NADHS and too much ATP. But then again, calcium, think of the muscles. Calcium is going to try to do what?

Helps to be able to form that, you know, allow for the muscle contraction. But we need ATP in order for the muscles to contract. So without the ATP, the muscles won't be able to contract.

So calcium is helping to activate this enzyme so we can speed up the ATP production. All right, cool. Now why did I want to mention this enzyme and say it's extremely important.

Okay, in your body alpha ketoglutarate is an integral component of an enzyme called histone demethylase. And this histone demethylase basically what histone demethylaces do is let's say here's the DNA here I have a sequence of DNA or something like that right and you know DNA is wrapped around histone proteins and histone proteins are basically very important for being able to control the organization of these DNA the gene expression and stuff like that. So these histone proteins are actually going to be having the DNA wrapped around them.

What histone demethylaces do is you might have methyl groups on these guys here which are basically controlling you know gene modification epigenetics and stuff like that. This hyone demethylace will come over and remove those methyl groups. Alpha ketoglutarate is a co-factor.

It's a co-actor for this hyone demethylase. Right in our body we have that enzyme right? So what was making the alpha ketoglutarate?

If you guys remember we were taking what we were having this alpha ketoglutarate which is going to be an important component of this step right here right helping to synthesize you know being a component of the histone demethylace if this alpha ketoglutarate right so remember we had the isoccitrate the isoccitrate was actually being converted what isoccitrate was being converted into alpha ketoglutarate right and that was done by the isoccitrate dehydrogenase enzyme but then alpha ketoglutarate is getting converted converted into what it's getting converted into sueninocoa through what alpha ketoglutarate dehydrogenase in a condition in which there is a mutant form of that alpha ketoglutarate dehydrogenase specifically the one which is having NADPH's involved with it not NADs NADPH's in a condition in which there is some type of mutation in this enzyme with the NADPHs it can actually convert instead of converting it into sueninoa and actually getting a lot of this alpha ketoglutarate you can get another molecule here and it's called two hydroxy glutarate why am I telling you this because two hydroxylutarate will come in and do what it'll bind and prevent this alpha ketoglutarate from being able to bind if alpha ketoglutarate can't bind onto the histone demethylis can you control the gene expression no if gene expression isn't controlled it can lead to tumors It can lead to uncontrolled cell growth primarily super dangerous one. You guys have probably heard of it called glycomomas. Glymomas are basically tumors that are occurring within the gile cells in the brain.

One of the really really dangerous ones is the astroytoomas or the glyopblastoma multiiform. So GBMs which are very very dangerous. You usually have an 80% uh metastatic rate and you're usually malignant and can cause you know unfortunate death.

But again understanding how something so small that you would think you know oh this just metabolism it can have such an amazing effect on your body. So again any type of mutation this alpha ketoglutarate dehydrogynase particularly with the NADPH1 instead of the NADH H1 can lead to the formation of a byproduct called two hydroxylutarate which can inhibit the alpha ketoglutarate from binding to the histone demethylase inhibiting this enzyme inhibiting gene expression and leading to uncontrolled cell growth and tumor formation. Okay.

Now we got that out of the way, let's move on to the next one. Now we got to take this sueninoa and I'm going to convert it into suenate. Okay, what happened here?

Okay, somewhere in this reaction. Oh, look at that alpha ketoglutarate going to suinico. What did we miss over here?

We had that COA. I should have a COA on this guy. What does that mean?

That means I added a COA onto this step. Let's add that in there. So there must have been a co-enzyme A being added into this step.

You know this alpha ketoglutate dehydrogenase. If you guys remember the pyuvate dehydrogenase complex, this enzyme functions in the exact same mechanism. So if you guys remember that enzyme, you'll remember how this enzyme functions.

Anyway, we add the COA in. Then look what happens. We we get rid of the COA.

So then we lose the COA in this step. But it's all for good reason. Just sometimes we might not like why it does this.

Well, what's happening here? Something really funky is happening. When we release the COA, it generates a little bit of energy, a little bit of potential energy that our body uses to take GDP and an inorganic phosphate and fuse that to form GTP.

Okay, it's cool. But then you know who comes in? ADP.

ADP is like, "Oh man, I'm gonna pit pocket this guy so hard. " So what does he do? ADB comes over here and steals the phosphate from the GTP.

ADP when he gains the phosphate, what does he turn into? He gains another phosphate. So, he turns into ATP.

Okay, that's cool. But what happens to the GTP? The GTP unfortunately goes back to GDP.

Okay, so it's a cool way of our body being able to generate ATP through what's called substrate level phosphorilation. So again, what is that called? It's called substrate phosphorilation which is completely different as compared to oxidative phosphorilation.

So substrate phosphorilation doesn't generate as much ATP as compared to oxidative phosphorilation. Okay. So that's happening in this stuff.

So we're developing ATP and that's coming because of releasing out the co-enzyme A which creates a little bit of energy to take GDP and inorganic phosphate fuse them together to make GTP. But then ADP comes over here, pit pockets that phosphate from the GTP and makes ATP which converts the GTP back into GDP. What enzyme is helping in this step?

Okay, this enzyme here converting suenyl COA into suinate. It's got a pretty cool enzyme. This is called specifically suenyl coa synthetase.

Okay, so you have the suenino coa synthetase enzyme and what this enzyme is doing is it's being involved in this step to stimulate the conversion of sueninoa into suxenate. Now, when we get that suenate, nothing crazy happens in this next step. But let's see what's happening here.

Nonetheless, okay, look, we're taking suenate and we're converting it into fumemerate. When we take suenate and convert it into fumemer, we have another enzyme. Look at this.

Look at this freak. Okay, this enzyme right here is special. You don't know why?

Look where he's actually anchored. He's anchored on the mitochondrial membrane, specifically the inner mitochondrial membrane, the christe. You know, this is actually called complex 2, enzyme complex 2.

It's a part of the electron transport chain, but we like to call it something else. We call it suinate dehydrogenase. Boom, light bulb.

What does that mean? Automatically, you should think FAD in this case to FADH2. But you guys are probably like, "Oh, dude, what?

You told me it was NAD. " any type of co-enzyme usually FAD or NAD is usually involved whenever you hear dehydrogenase. Okay.

Now because I'm forming FADH2 this is going to be helpful in energy production but you know what else is also helpful for this you know in certain conditions it's called fiochromocyto called fo chromosytoma there's some type of mutation in this enzyme an alteration or mutation this enzyme can cause a situation where you form a neuroblastoma it's usually benign meaning it's not metastatic it doesn't spread But this fiochromosytoone is usually a tumor that develops within the adrenal medulla and it causes an excessive amounts of epinephrine and norepinephrine to be produced which causes an extreme hypertensive crisis. So a very very dangerous condition but just seeing any type of mutation this enzyme can lead to this condition of fiochromosytoma. All right cool.

So again remember that this is enzyme complex 2. It's a part of the electron transport chain and it's converting FAD to FADH2 but it's also reversible. So this reaction can be reversible.

All right, cool. So that's that step. Now we're going to take the fumemerate and we're going to convert that into the mali.

Okay, this enzyme is really really simple. Nothing crazy about this enzyme. This enzyme is called fummerase.

And look, we got Humpty Dumpty. He's sitting on this reaction. Humpty Dumpty is actually going to do what?

He's going to throw some water into this reaction. He's like, "Ah, let me help out in this reaction to the best of my abilities. " And he throws water into this reaction.

But again, remember that this reaction is reversible. So what does he do in this reaction? Humpty Dumpty takes and throws water into this reaction to convert fume into mal.

Now you might be like, "Okay, simple. Must not be that important of an enzyme. " He is very important.

you know in the in a condition which there's a deficiency in this enzyme it can lead to the formation of what's called leomas or leomyomas too and leomas are usually going to be tumors that develop within smooth muscle tissue usually they're benign perfect example this one is is they also call them fibroids but it's some type of uterine very very common in the uterine smooth muscle and even in the kidneys okay so this can happen in the uterine smooth muscle and it can happen in the kidneys, but usually there's some type of leoma and again just a deficiency in this enzyme can cause that significant change. Unbelievable. Okay, so now we got malate.

Malate has this Hades looking enzyme. Look at this. Look at this freaking guy.

This guy right here is a cool enzyme. I like him. He's called malate dehydrogenase.

You guys should automatically think again NAD positive2 NADH. So what's happening here? I'm taking NAD positive and I'm converting it into NADH.

Why? Because there is a dehydrogenase enzyme present. When there's a dehydrogenous enzyme present, it's converting NAD positive to NADH in this step.

This enzyme is also reversible. So this reverse reaction can occur OA to mali. And we'll see that in throughout more videos where we cover a little bit on gluconneioenesis and even electron transport chain.

Okay, now that we've done that, we've covered all of these different enzymes that are involved in this in these steps here. Now, one other thing I want to do I want to tell you guys is is that when I'm taking this acettocoa, what am I doing, right? I'm taking this acceto I'm combining with the oxalo acetate and having it react with citrate centase to form citrate.

Citrate is reacting with a conantase to make isoccitrate. Isocitrate is going to be acted on by isoccitrate dehydrogenase to make alpha ketoglutarate. Alpha ketoglutarate gets converted into sueninoa when acted on by alpha ketoglutate dehydrogenase.

The suino sueninocoa synthetase is going to be taking sueninoa and converting it into suxenate which generate a little bit of ATP in that step and then suxenate is converting it into fumemerate and then fummerate is being converted into malate and malate back to OA. How many acetto should I really be having going through this this cycle? This is crucial.

I have two pyuvates. Well, two pyuvates get converted into two acettocoas. That means I make two turns.

Well, if I make two turns, don't I really develop two FADH2s? Don't I really develop two NADH's? And don't I develop another two NADH's right here?

And another two NADH's right here. And technically two ATP and two COAs, right? and two COAs being added.

Okay, so how many CO2s did we generate out of this? We generated two in this step and we generated two in this step. So 2 plus 2 is four.

So we got four CO2s out of this. Okay, what about NADH's? I generated six NADH's.

How did I generate six NADH's? Let's look. We generated two NADHs in this step going from Mali to oxalo acetate, right?

So that's two. I generated two NADHs in this step going from isoccitrate to alpha ketoglutarate. That's four.

And I generated two more NADHs going from alpha ketoglutarate to sueninoa. That's six. Then what was the last thing that we generated?

Two FADH2s. Okay, cool. So I got two FADH2s.

Last thing, how many ATP did I generate? Two ATP. And by what type of phosphorilation?

Substrate phosphorilation. So again, I'm generating by substrate phosphorilation. And where is that happening?

That's happening when I'm going from sueninal COA to suinate. Remember, I'm taking the GDP to GTP and having the ADP pick off that phosphate to form ATP. Two of them by substrate level phosphorilation.

So out of this, this is going to be the main products that you'll get out of this. And these NADHs and FADH2s will go and take these hydride ions to the electron transport chain. Will they be used to make ATP by oxidative phosphorilation?

All right, ninj. So, we went over a lot of information in this video. I hope it all made sense.

I hope you guys did enjoy it. If you did, please hit the like button, subscribe, put a comment down in the comment section. I nerds.