One of the early steps in the urea cycle by which ammonia is...

One of the early steps in the urea cycle by which ammonia is excreted from the body is the reaction of bicarbonate ion $\left(\mathrm{HCO}_{3}^{-}\right)$ with ATP to yield carboxy phosphate. Write the reaction, and draw the structure of carboxy phosphate. You can check your answer in Figure 20.4

Key Concepts

Bicarbonate Ion Activation

Bicarbonate ion (HCO3–) plays a critical role in metabolism by participating in reactions where it is activated by ATP. This activation forms reactive intermediates like carboxy phosphate, which are essential for incorporating inorganic carbon into organic molecules during processes such as the urea cycle.

Carboxy Phosphate Intermediate

Carboxy phosphate is a high?energy acyl phosphate intermediate formed when ATP reacts with bicarbonate. This intermediate contains a mixed anhydride bond that stores significant energy, which is then harnessed to drive further reactions in metabolic pathways, including the subsequent steps of the urea cycle.

Urea Cycle

The urea cycle is a metabolic pathway that converts toxic ammonia into urea, a less harmful compound that is excreted from the body. This process is essential for nitrogen detoxification in mammals, primarily occurring in the liver, and involves several enzymatic reactions that incorporate components like ammonia and bicarbonate.

ATP Hydrolysis and Phosphoryl Transfer

ATP (adenosine triphosphate) serves as the primary energy currency in cells and is involved in many biosynthetic reactions. Its hydrolysis releases energy that drives reactions by transferring a phosphoryl group to substrates, thereby activating them for subsequent chemical transformations.

Transcript

00:01 So we have the following reaction here.

00:03 We're given arginosuxinate, and when treated with base, we get the following products.

00:07 We get arginine and fumarate.

00:09 So the question asks us to propose an aeropushing mechanism for something that could explain what's going on here in this biochemical reaction.

00:18 So what's going to happen here is we're going to have an elimination reaction.

00:22 More specifically, we're going to have an e1cb type elimination reaction.

00:27 We're actually going to form a carb anion.

00:29 So i'm going to go ahead and show our base coming in and deprotonating this hydrogen, and then the electrons are going to get pushed towards this carbon to form the carb anion, and we're going to get the following structure.

00:45 All right, it's going to be a long one here, like that.

01:12 So now this carbon has a lone pair here, and it has a negative charge.

01:18 So now it's a carb anion.

01:30 Okay, and then this nitrogen has a hydrogen on it.

01:34 And then we also have ammonium coming, going away from us here, which has a positive charge.

01:43 And then we have hydrogen coming towards us here.

01:52 All right.

01:52 So i believe that's everything there.

01:54 And so the next step in this reaction here is that this loan pair is going to form a bond here.

02:01 It's going to get pushed towards the carbon -carbon bond here.

02:04 And subsequently, oops, sorry...