The Urea Cycle - Video Tutorials & Practice Problems
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1
concept
The Urea Cycle Concept 1
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In this video, we take a look at the urea cycle in terms of an overview. Now, here we're going to say the urea cycle converts the ammonium ion to urea using ornithine as a carrier. Now, here we're gonna say the carbon source comes from carbon dioxide, which again comes from the mitochondrial matrix. We're gonna say our nitrogen atom source comes from the ammonium ion as well as aspartate. And we're gonna say here that the energy cost of the process is four A TPS. We'll see why that is. Now if we take a look here, we have our orine acting as our carrier and we're gonna say, remember the ammonium ion, we're going to have to use carbon dioxide from the mitochondrial matrix as well as the consumption of A TP in order to change it into our carbo mo phosphate. Now, here to do that, we use two A TPS which produces two AD PS. We're going to say here our carbon oil phosphate is created and that goes into the urea cycle. We're gonna say we're gonna go through these different steps of the urea cycle, which we'll talk in greater detail later on but we know that at the end of it, we're gonna produce as a byproduct's which is produced within the cy assault. One important thing is, remember we have our phase A and our phase B, phase A is our preparation phase. And then here, when we're talking about phase B, we're talking about our conversion phase. This is where we're gonna produce our urea from our carbo oil phosphate and aspartate. If we look here, a TP is also consumed in this step two here. But here A TP becomes a MP. So we've lost two inorganic phosphates in this process and then um aspartate comes into the cycle so that we can make urea at the end. So just remember we are utilizing how many A TP molecules 32 here and one here. And we are releasing how many inorganic phosphates as a result? Well, were you releasing two inorganic phosphates? Here, each one of these A TP here releases one of them together. That's two. And over here, we're still releasing two inorganic phosphates, but it's coming from one A TP. Instead of going from A TP to AD P, we're going from A TP to A MP, right? So again, this is just a quick overview of the area cycle before we go into greater details, which each of the steps involve
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example
The Urea Cycle Example 1
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Here, it says give the number of A TV molecules consumed in the cycle and the actual energy cost of the process. Now, if you can recall the overview of the cycle, remember we saw two A TPS when we're talking about the ammonium ion being converted into the carbon oil phosphate group. So we know we have two A TPS. We also know that another A TP molecule is involved with aspartate incorporating itself into the urea cycle. So that would be a total of three A TP molecules. So it means our answer is gonna be either B or D. So the number of A TV molecules is three. But what is the actual energy cost of the process? If we think of the energy cost involved in releasing our inorganic phosphate groups, how many inorganic phosphate groups are released? Well, remember we have two A TPS becoming two ad PS. So that means we'd have to release two inorganic phosphates. We'd have to cut those bonds in order to release those inorganic phosphates. And then we also have that one A TP molecule, but it itself becomes a MP, it loses two inorganic phosphate groups as well. So that's four and organic phosphates that are produced, that shows us the actual energy cost involved. So the actual energy costs would be four. So that would mean option D is our final answer.
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Problem
Problem
Which amino acid provides the NH4+ for the formation of carbamoyl phosphate?
A
α-ketoglutarate
B
Glutamine
C
Glutamate
D
Aspartate
4
Problem
Problem
Which of the following amino acids is not a part of the urea cycle?
A
Asparagine
B
Argininosuccinate
C
Arginine
D
Ornithine
5
concept
The Urea Cycle Concept 2
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Here we have phase A which deals with preparation. Here, we're gonna have the synthesis of our carbo oil phosphate which will abbreviate AC P from the ammonium ion and carbon dioxide and it represents an energy consuming step. Now, we've heard that mitochondria is the energy powerhouse of the cell. The mitochondria also is a site of the creation of carbon dioxide. Remember through pyruvate oxidation as well as the citric acid cycle or creb cycle, we have the generation of carbon dioxide. This serves as our source of the carbon atom. Here we're going to say the enzyme have a moil phosphate synthetase catalyzes the reaction. Remember a synthetase is going to help to link molecules together through the use of energy. We're gonna say that two A TP molecules are hydrolyzed to produce two AD PS as well as one in organic phosphate. Now, here we are creating two bonds. One of them being a highly energetic bond. That's why two A TPS are required. One A TP would not supply enough energy in order to convert our ammonium ion with the incorporation of carbon dioxide into our carbon oil phosphate group. So here if we take a look, we have our ammonium, we have carbon dioxide to the use of our enzyme, which again is the substrate name followed by the class of enzyme which is in this case, a synthese because we're making links between molecules to the use of energy. We have to use this class of enzyme. We'd have our two A TP which become two A P as well as our inorganic phosphate. So here we would write the inorganic phosphate within this little box. All right. So this will give us our carbon oil phosphate. This will represent the beginning of phase A in terms of preparation.
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concept
The Urea Cycle Concept 3
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Here in phase B, we deal with conversion. Here, we're going to say the urea cycle is a cyclic pathway consisting of four reactions. We're gonna say reaction one happens within the mitochondrial matrix. Here we have carbo moy phosphate being changed into cr reactions. 23 and four occur within the cytosol itself with the end reaction helping us to produce urea. Now, here the cycle basically utilizes three nonprotein amino acids in order to function. So just remember when it comes to urea cycle, we have phase A which deals with preparation and then phase B where we have these four reactions. That is where we talk about conversion, right. So here that we know the general overview of the urea cycle will go deeper in terms of these different types of reactions.
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concept
The Urea Cycle Concept 4
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In this video, we'll talk about reaction one when it comes to phase b of the urea cycle. Here, we're dealing with transfer in it. The carbon oil group is transferred from CP or carbon oil phosphate to ornithine to produce citrine. Now, here it's catalyzed by the enzyme OTC. For short, it's a mouthful. So it's easier to call it OTC which is ornithine trans carbo oil ace. So we're gonna repeat that just to OTC. So if we take a look at this reaction, we have our ornithine which remember represents our carrier. We have our carbon oil phosphate, it will release our inorganic phosphate group. We have our enzyme being used otc tralene. Here. Again, it's going to gain the carbon oil group, which is basically what's shaded here in green. So now the nitrogen is gonna be connected to the carbon that carbonel is still connected to its NH two group. This represents our citroen. Now cen itself is transported outside the mitochondria into the cytosol so that we could continue with reactions 23 and four
8
example
The Urea Cycle Example 2
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Here it says name the amino acid form when ornithine reacts with carbon oil phosphate. Now remember what happens here is that we're gonna have our ornithine going to gain the carbon oil group doing this will help to create the only amino acid in reaction one that's produced, which would be croly citrine is then transported outside of the mitochondria into the cytosol so that we can continue with the urea cycle which encompasses reactions 23 and four. Remember at the end of reaction, four, our final product will be the urea which is then excreted out in our urine. So here, the only answer is option B.
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The Urea Cycle Concept 5
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Here, we're going to say that reaction to a phase B of the cycle is dealing with condensation. Here, citrine undergoes condensation with aspartate to produce geno succinate. Now here this is catalyzed by the enzyme Argen succinate synthese. Again, remember energy is being used in order to do this or we have molecules that are being linked together. So synthetase is the class of enzyme required. The name itself. Remember is the substrate followed by the class of enzyme. Now, in this process, one A TP is hydrolyzed to one A MP and two inorganic phosphates. This is equivalent to saying you have two A TP becoming two AD P. If we take a look here, we have our tralene, it gained this carbo oil group from our ortin molecule and reaction one. If we take a look here, we have our aspartate, we utilize a TP in order to produce a MP and two inorganic phosphates, we have our enzyme that's being utilized. We're gonna say as a result of this, we're gonna create our connection of Argen Argen succinate. Basically, we're gonna have this carbon here single bonding itself to nitrogen nitrogen here. Ideally wants to make three bonds in order to stay neutral. So it's just gonna be an NH group. So this represents our Argen uh succinate group. And then here, succinate, remember itself, it is the deproteinate form. The part that the carbolic acids have given away the H plus, it's a di carbolic acid that's given away, it's two acidic hydrogens. So we have two carboxylate ends here. So this represents our succinate molecule.
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concept
The Urea Cycle Concept 6
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Now, reaction three deals with cleavage. Here, we have Argentino succinate lying and it catalyzes the cleavage of Argen nino succinate to produce arginine or arginine. Now, remember alys here can be utilized within an additional elimination reaction. Here's gonna help to sever the link between a carbon atom and an element that is not carbon. In in this case, it's gonna sever this connection here between this carbon and this nitrogen. So here we have our Argentino succinate. We're utilizing our enzyme here when we sever that link nitrogen needs to continue to make three bonds. So it's gonna become an NH two, we're gonna say here that our aspartate carbon chain is lost as a fumarate. So when we sever this connection in our reactants, we create arginine and our fate as two products, right? So again, this represents our cleavage where we're cutting, cleaving our Argen succinate to form arginine and umer as products
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concept
The Urea Cycle Concept 7
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The funnel reaction deals with a hydrolysis reaction. Four. Here, the enzyme arginase hydrolyzes arginine to ornithine and urea. So here we have our arginine, we're gonna utilize our Argena. We're gonna bring in water in order to do this hydrolysis. Remember, we're utilizing water in a hydrolysis reaction. When we do this, we're going to create are ornithine and aurea. Remember, aurea is a carb connected to two NH twos, right? So if we take a look here, we're severing the connection here. This carbon here is this carbon here. It possesses its two NH two groups still. And it's gonna gain a carbon yield in order to make urea as our by-product that's excreted through our urine. The ornithine that's created, it's transported back to the mitochondrial matrix to begin the urea cycle again. So here, the ornithine in this step is being regenerated. We had it earlier in terms of this cyclic process and now it's recreated in reaction four, right. So, reaction four, here we're doing hydrolysis in order to create our carrier ornithine once again, as well as our waste product in the form of urea, which again is excreted through our
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example
The Urea Cycle Example 3
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Here it says which of the following statements explains the structure of the carbon oil group accurately. All right. So our carbon oil phosphate, well, it is a carbonyl and it has an NH two group attached to it. And then we'd say that that carbon carbon is connected to an oxygen as well as an inorganic phosphate. This is what our CP is our carbon oil phosphate group. But here they're not asking for AC P. They're just asking for the carbon oil group. Carbon oil group would just be this portion. Here, we're not looking at the oxygen with the inorganic phosphate portion. So if we take a look, which one best describes it here, two NH two groups bonded to the carbon group. No, that is a definition or a description of the urea molecule. So that doesn't work two age groups bonded to a carbonel group. That also doesn't describe this an NH two group bonded to a carbon group. All right. So here's our NH two group connected to a carbonel group. That is what a carbon oil group is. So this is our answer. But let's look at D just to make sure a carbon group bonded to one NH two group and 10 group. That doesn't describe what a carbon oil group is. So here, the best answer would be option C.
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Problem
Problem
What is the function of aspartate in the urea cycle?
A
Produces CO2 for carbamoyl phosphate synthesis.
B
Provides –NH2 group as ammonium ion.
C
Produces succinate for citrulline formation.
D
Provides the second nitrogen atom for urea.
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Problem
Problem
Which one of the following sentences is an incorrect description of a reaction in the urea cycle?
A
Citrulline condenses with aspartate to produce argininosuccinate.
B
Hydrolysis of arginine produces urea and regenerates citrulline.
C
Transfer of carbamoyl group from carbamoyl phosphate to ornithine produces citrulline.
D
Argininosuccinate undergoes cleavage to produce arginine and fumarate.
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concept
The Urea Cycle Concept 8
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Now, the urea cycle is made up of four reactions. Yes, but it has a lot involved with it. We have different types of metabolites and different types of enzymes involved to help us memorize these. We're gonna utilize two memory tools. The first memory tool is gonna help us memorize the metabolite names. So here we're gonna say when it comes to memorizing or remembering the urea cycle reaction to the Urey Cle can be remembered by memorizing the metabolite names. So before we talk about this memory tool, just a little bit of history about me. So I am Jules Bruno Junior. Uh My father's name is Jules Bruno. My father was a cab driver for nearly 30 years in Miami Florida and different times after school when he picked me up, I'd be in the cab with him. I'd hear interesting conversations with each of his fares and this kind of inspires this memory tool. So if we take a look at this memory tour, we're gonna say here that ordinary he pooling citizen and we're gonna say here as Spires Arranged, it's arranged success and it's gonna fuels arguments and otters opinions. So ordinary carpooling citizen in a cab, we're gonna say aspires, arranged success. So that can be any success of the people driving the, um, being ridden in the cab. That could mean a lot of things fuels arguments. I've heard some interesting debates between the people in the car, the people. We're on the phone with, uh, my dad talking about them, with them with different things, utters opinions, strong opinions, sometimes being uttered between people in the car. Um So it's always quite interesting but how does this fit to the urea cycle? Ok. So ordinary or we start with ornithine our carrier molecule, we're gonna say car pulling car carbo oil phosphate, carp citizen is citroen. And if we look these three, all part of reaction, one here goes one next, we've have aspires, arraigned success, aspartate aspires arranged. You were talking about Argentino succinate success. We have succinate involved. Ars Argen succinate fuels arguments, fuels fumarate arguments. Arginine. Again, if we go here, this is reaction two, which is our aspartate reaction two is our aspartate and then ar gino succinate reaction three, three is fate and arginine. And then finally reaction four otters opinions. We have ya and ornithine being regenerated for reaction four. Remember arginine, we utilize the enzyme arginase that helps to produce urea as a product that we excrete in urine and then regenerates ornithine. So again, utilize this memory tool. Think about a cabbie picking up different fares, hearing interesting conversations, hearing opinions being exchanged maybe between the cab driver and the passengers or the passengers amongst one another. Right. So this helps to frame the different types of metabolite names within the Urea cycle.
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concept
The Urea Cycle Concept 9
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Here, we're going to say the name of the enzyme can be predicted by knowing the substrate and the type of reaction here, our reaction types are transfer, condensation, cleavage and hydrolysis. And our memory tool two here will be train conductor cleans house. So train conductor cleans house. Here are hints correspond to the the different reactions. So hint one is reaction one, this will be reaction 23 and four for reaction one which relates to um hint one, we have transfer and it's catalyzed by the ornithine trans carbo Mala which is OTC and two, we have condensation, it's catalyzed uh by our synthetase cleavage. We're cleaning. This is catalyzed by our lie ace and then four reaction four hint four hydrolysis is catalyzed by our Argena. Again, use this in conjunction with your memory tools one in order to line things up so that you can know for example, hint four, which is reaction four, we're talking about our arginine becoming our orine being recreated as well as urea. So because it's arginine, we know that arginase has to be the enzyme that's being used. So again, use this memory tool in conjunction with uh memory tool one to help guide you to the different types of metabolites involved and thereby understand the enzymes needed.
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example
The Urea Cycle Example 4
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Here. In this example, it says, what are the products of the third reaction of the urea cycle? In order to answer this question, we need to think, think about memory tool. One. So reaction three deals with line three and a memory tool. Uh One, line three is fuels arguments. And if we take this portion and this portion that tells us the metabolites involved in that reaction and thus the products form. So F fuels stands for fumarate arguments. Arg is arginine. That would mean that the answer here would have to be b although he has frate as well aspartate is not arg arguments so it doesn't work. So the other option is not even close. So again, the final answer would have to be option B fumarate and arginine which corresponds to fuels arguments.
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Problem
Problem
Which of the following metabolites is hydrolyzed in the urea cycle to produce ornithine and urea?
A
Citrulline
B
Arginine
C
Aspartate
D
Argininosuccinate
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Problem
Problem
Which enzyme catalyzes the reaction of citrulline with aspartate to produce argininosuccinate?
A
Succinate dehydrogenase
B
Argininosuccinate lyase
C
Argininosuccinate synthetase
D
Arginine oxidase
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Problem
Problem
Write the total number of amino acid metabolites in the urea cycle. How many of those amino acids are not found in proteins?