Amino Acid Catabolism: Carbon Atoms - Online Tutor, Practice Problems & Exam Prep

Amino acid catabolism involves the breakdown of amino acids into carbon skeletons, which can either synthesize glucose through gluconeogenesis or ketone bodies via ketogenesis. Amino acids are classified as glucogenic, ketogenic, or both. Key intermediates include pyruvate, oxaloacetate, and acetyl-CoA, which play crucial roles in energy production. Memory tools can aid in recalling the amino acids associated with these intermediates, enhancing understanding of metabolic pathways and their significance in energy metabolism.

Amino Acid Catabolism: Carbon Atoms Concept 1

In this video, we're going to take a look at amino acid catabolism in relation to carbon atoms. Now, here amino acids can be categorized based on whether they synthesize glucose or ketone bodies. Remember, in amino acid catabolism, when we talk about the carbon skeleton, we have 2 fates. One that deals with the citric acid cycle and gluconeogenesis, where we have the creation of glucose, or we have ketogenesis, which deals with the creation of ketone bodies. Now here, when we talk about our amino acids, we have our glucogenic and ketogenic amino acids. Glucogenic amino acids only synthesize glucose. Ketogenic amino acids only synthesize ketone bodies. If we take a look at our chart here, we have glucogenic versus ketogenic amino acids. The ones in blue, these are strictly our amino acids that are glucogenic in nature. Then we have those that are ketogenic and then those that are both.

Luckily, we have a memory tool to help us recall how to organize these different types of amino acids. And our memory tool is simply FIT. So FIT, F-I-T-T-T. So, triple T, we're dealing with Threonine, Tryptophan, and Tyrosine, our 3 amino acids that begin with T. I, I here is Isoleucine, our amino acid that begins with I. And here we're dealing with Phenylalanine. If you sound it out, Phenyl sounds like an F. So F-I-T. These are our amino acids that are both glucogenic and ketogenic in nature.

Alright, so we've figured out those. Next, ketogenic. This one is also easy to remember because our ketogenic ones are the only ones that begin with L. So Leucine and Lysine are 2 ketogenic amino acids. That would mean that all the other amino acids have to be glucogenic in nature. Right? So just remember FIT. FIT helps us to remember we're dealing with Phenylalanine, we're dealing with Isoleucine, and then our 3 T's, Threonine, Tryptophan, and Tyrosine. When it comes to ketogenic, it's only the amino acids beginning with L. Everyone else will be glucogenic in nature. Alright. So keep that in mind when trying to organize these different types of amino acids.

Amino Acid Catabolism: Carbon Atoms Example 1

In this example, it says, label each amino acid as Glucogenic (G), Ketogenic (K), or both with (B). Alright. So remember when it comes to both, we use the memory tool of fit, FITTT. F here is Phenylalanine. I here is Isoleucine. T are only 3 Amino Acids beginning with T. So we could say Threonine, Tryptophan, and Tyrosine. So, if we take a look at our options, here goes Tryptophan (T), this has to be the one with both. We don't see Phenylalanine anywhere. We don't see Isoleucine anywhere. We don't see another amino acid beginning with T. So this is the only option that has both as an answer. Right. So then we're left with, Serine, Lysine, and Glutamine. Remember, Lysine begins with L. Only the Ketogenic Amino Acids begin with L. Lysine is one of them. Leucine would be the other one. So this is K. Serine doesn't start with an L. Glutamine doesn't start with an L. Neither one is part of our memory tool of fit. Therefore, they can't be ketogenic in nature and they can't represent both. So by default, they are glucogenic. So both of them will get G as their answer. Alright. So this is how we'd sort out these different types of amino acids being glucogenic, ketogenic, or both in terms of nature.

Identify amino acid that is considered to be glucogenic but not ketogenic.

• A. Phenylalanine
• B. Leucine
• C. Tyrosine
• D. Aspartate
• E. Lysine

Amino Acid Catabolism: Carbon Atoms Concept 2

Here in this video, we're going to continue our discussion of amino acid catabolism in relation to carbon atoms, and we're going to pay attention to the fate of amino acid carbon atoms. But first, recall that transamination produces an Alpha Keto Acid. It produces a new amino acid as well, but we're concerned with the Alpha Keto Acid. Here, this represents the amino group that's been left out. So we're looking at our Carbon Skeleton. The carbon atoms of an alpha keto acid are converted to one or more of the seven energy-producing intermediates. Now as a disclaimer here, your professor may not require you to memorize all the intermediates involved in the amino acids connected to them. But if you are supposed to memorize all the intermediates and the amino acids connected, we do have memory tools we'll go over later to help you memorize them. Now, here we're going to say that the Citric Acid Intermediates can be used to synthesize Glucose through gluconeogenesis. And we're going to say Acetyl CoA and Acetyl Acetyl CoA can be used to synthesize ketone bodies through ketogenesis. Now based on metabolic pathways, some amino acids can synthesize both. Remember, we've talked about this before. We have our amino acids that are glucogenic, ketogenic, or a combination of both. When it comes to both, we remember fit. Which remember is f I t t t. Or we have Phenylalanine, we have Isoleucine, and then three amino acids beginning with T. Remember that our ketogenic ones are the ones that begin with L which are Leucine and Lysine and then all the other remaining amino acids are glucogenic in nature. This means that a vast majority of the amino acids, they're trying to create glucose. Now, if we take a look at this large structure here, we have in blue our pyruvate, we have Oxaloacetate, we have Alpha Ketoglutarate, we have Succinyl CoA, fumerate, and again back to oxaloacetate. These are the citric acid cycle portions that we have. Now remember, what's in the blue boxes represents our glucogenic amino acids. What's in these kind of like fuchsia pinkish boxes? Those are our ketogenic ones. Remember, those are the only ones that begin with L, so Leucine and Lysine. And then both would be the purple one here. If we take a look here, we can see that Alanine and all these amino acids, they help to make pyruvate here. Pyruvate itself can do one of two things. Pyruvate can go towards Acetyl CoA, which in itself is in a reversible reaction with Acetyl Acetyl CoA. These can help to make ketone bodies. Here, that makes sense because we have these in the purple boxes, which can be ketogenic or glucogenic in nature and then these that are only ketogenic in nature. So, everything here is Ketogenic because they're going to help to make Acetyl CoA and Acetyl Acetyl CoA which eventually can help make Ketone bodies. Now, here Pyruvate can also be changed into Oxaloacetate, which is part of the Citric Acid Cycle by utilizing the enzyme Pyruvate Carboxylase. Now, this Oxaloacetate itself, it is important because it can lead to the generation of glucose. And through the digestion of glucose, we can help make high energy ATP as our final molecule. Now here, Acetyl CoA itself, if we look, it could feed in the Citric Acid Cycle. But here, Acetyl CoA would combine with Oxaloacetate and that would feed directly into Alpha Ketoglutarate. Because of this, we're going to say that when it comes to Acetyl CoA, it cannot create glucose because it uses oxaloacetate at the beginning of the citric acid cycle. So it'll use an Oxaloacetate in order to go through the Citric Acid Cycle and produce an Oxaloacetate at the end. So the net gain is zero. Now, here if we take a look, we can see that again, these are ketogenic in nature to help make ketone bodies. And then a vast majority of the other amino acids, they come in later on in the citric acid cycle. So, here they can help moving this way create Oxaloacetate which again can lead to the generation of Glucose. Glucose, from this image, we can see again a vast majority of the amino acids they're trying to make glucose. Glucose can lead to high energy production ATP later on through digestion. Right? So, here, this is just a way of organizing how some of the amino acids line up and what kind of intermediates they help to make in the continuation of the generation of either ketone bodies or glucose. Alright. So here we're going to utilize this chart in terms of answering a sample of example and practice questions.

Amino Acid Catabolism: Carbon Atoms Example 2

Here in this example question, it says, select the correct statement about amino acid intermediates. Alright. So Tyrosine is only ketogenic because it produces Acetyl CoA. Now, remember our Ketogenic ones are the ones that begin with the letter L. So Leucine and Lysine. Based off of just that, we know that this answer cannot be true. Tyrosine doesn't begin with the letter L. Also, we know that it can only be ketogenic in nature because it is surrounded by a purple box. Also, in terms of our memory tool fit, it represents one of these amino acids beginning with T. Aspartate is considered glucogenic and ketogenic because it degrades 2 intermediates of the Krebs Cycle. So here, fit is the memory tool we use for the amino acids that are both ketogenic and glucogenic in nature. Aspartate, A, it's not one of the letters here. So it couldn't be both Glucogenic and Ketogenic in nature. Also, if you take a look at the chart, we see that it has a blue box around it meaning that it is only Glucogenic in nature. Isoleucine can be used to synthesize Glucose and Ketone bodies due to 2 different intermediates it can form. That is true. Based on FIT, I, we know that it is both ketogenic as well as glucogenic in nature, so it can form glucose and ketone bodies. And if it can produce those two things, it has to be done due to 2 different intermediates it can form. So, this statement is true. Next, Pyruvate is the product of only Glucogenic Amino Acids. Well, looking at the chart that we see that there are, Threonine and Tryptophan, which are in purple boxes. They are both ketogenic as well as glucogenic in nature. So this can't be true. It can't only be glucogenic amino acids. If it were, all those Amino Acids above pyruvate would have to be in blue boxes, which they are not. So, this is not true. So again, here the only answer that's true is option C.

Amino Acid Catabolism: Carbon Atoms Concept 3

So here, we're going to utilize some memory tools to help us recall the different types of intermediates involved as well as their amino acids. So, here we have memory tools 1 all the way down to 7.

Memory tool 1 deals with pyruvate. The amino acids attached to it are Glycine, Tryptophan, cysteine, serine, threonine, and alanine. The way we can memorize this is that we have pirates gliding in water and we're going to say 16 sirens throwing algae. So pirates, pyruvate, gliding glycine, Tryptophan, its one letter code is w, 16, 16, sirens, siren, siren close, throwing, threonine, algae, alanine.

Memory tool 2: Next intermediate is Oxaloacetate. Here, we have aspartate and asparagine. Here, we'd say that it is oxen, and we're going to say, aspire to eat asparagus. So oxin ox, oxaloacetate, aspire aspartate, to eat asparagus, asparagine.

Memory tool 3: Alpha-ketoglutarate. We have proline, histidine, arginine, glutamate, and glutamine. Here, we'd say the memory tool is Alfred eating protein to fuel his arms and both glutes. So Alfred Alpha, ketoglutarate, proline protein, histidine his, arginine arms, and both glutes. There's 2 glutes, glutamate and glutamine.

Memory tool 4: Succinyl-CoA is connected to Valine, Methionine, and Isoleucine. Here, our memory tool would be succulent, and we're going to say vanilla melon ice cream. Succulent succinol vanilla valine melonmethionine. Isoleucine is ice ice cream.

Keep going. Memory. So it's a lot. It's a lot. But these are the best tools that you can use to help you memorize the groupings of the intermediates and their respective amino acids.

Fumarate, we have Tyrosine, Phenylalanine, and Phenylalanine. So here, we'd say, furious tires flying on asphalt. So here, I like that one. So furious fumarate tires, tyrosine, flying phenylalanine, aspartate, asphalt.

Next, memory tool 6, Acetyl-CoA with its amino acids like isoleucine, leucine, threonine, and tryptophan. We have ACE is losing a third third-place trophy. So ace, acetal is losing, iso, leucine, third so losing third, leucine, third is threonine, trophy is tryptophan.

Then memory tool 7, Acetyl-CoA. We have Tyrosine, Leucine, Lysine, tryptophan, and Phenylalanine. So here, this would be a saline tying loose knots with flowers. So acetyl acetyl-CoA, acetylenes here, tying tyrosine, loose, leucine, knots lysine, with, again one letter code for tryptophan is w, phenylalanine flowers.

Alright. So here, these are the memory tools you can utilize. Again, talk to your professor. Do you need to know all the intermediates? Do you need to know all the amino acids connected to them? If you do, these are the memory tools you need to utilize to remember their groupings.

Amino Acid Catabolism: Carbon Atoms Example 3

Here it says, select the correct list of amino acids from which pyruvate can be metabolized. So pyruvate, this deals with memory tool number 1. Memory tool number 1 says, pirates lighting in water 16 sirens throwing algae. So, pirates' pee is pyruvate. Gliding, gly is glycine. In water, one letter code, W is for tryptophan. 16 is cysteine. Sirens is serine. Throwing is threonine. And then algae AL is alanine. So pyruvate or metabolite, and these are the amino acids connected to it. If we look at our options, the only one that has these groupings would have to be option C. So, option C would be our final answer.

Which intermediate can be produced from degradation of carbon atoms in glutamate?

• A. α-Ketoglutarate
• B. Pyruvate
• C. Acetyl CoA
• D. Succinyl CoA

Here’s what students ask on this topic:

What are the key differences between glucogenic and ketogenic amino acids?

Glucogenic amino acids are those that can be converted into glucose through gluconeogenesis. They enter the citric acid cycle and eventually lead to the production of glucose. Examples include alanine, glycine, and serine. Ketogenic amino acids, on the other hand, are converted into ketone bodies through ketogenesis. They are typically converted into acetyl-CoA or acetoacetyl-CoA. Examples include leucine and lysine. Some amino acids, like isoleucine and phenylalanine, are both glucogenic and ketogenic, meaning they can produce both glucose and ketone bodies.

How do memory tools help in recalling amino acids associated with metabolic intermediates?

Memory tools are mnemonic devices that simplify the process of recalling complex information. For example, to remember the amino acids associated with pyruvate, you can use the phrase 'pirates gliding in water,' which stands for Glycine, Tryptophan, Cysteine, Serine, Threonine, and Alanine. These tools create vivid mental images or associations that make it easier to remember the specific amino acids linked to each metabolic intermediate, such as pyruvate, oxaloacetate, and acetyl-CoA. This aids in understanding metabolic pathways and their roles in energy production.

What role do citric acid cycle intermediates play in amino acid catabolism?

Citric acid cycle intermediates play a crucial role in amino acid catabolism by serving as entry points for the carbon skeletons of amino acids. For instance, pyruvate can be converted into oxaloacetate or acetyl-CoA, which then enter the citric acid cycle. Oxaloacetate can lead to glucose production through gluconeogenesis, while acetyl-CoA can be used for ketone body synthesis. Other intermediates like alpha-ketoglutarate and succinyl-CoA also integrate amino acid carbon skeletons into the cycle, facilitating energy production and metabolic balance.

Why can't acetyl-CoA be used to synthesize glucose?

Acetyl-CoA cannot be used to synthesize glucose because it enters the citric acid cycle by combining with oxaloacetate to form citrate. During the cycle, acetyl-CoA is fully oxidized to CO₂ and H₂O, and no net gain of oxaloacetate occurs. Since oxaloacetate is required for gluconeogenesis, the use of acetyl-CoA in the citric acid cycle does not contribute to glucose production. Instead, acetyl-CoA is primarily used for energy production and ketone body synthesis.

What are the seven energy-producing intermediates in amino acid catabolism?

The seven energy-producing intermediates in amino acid catabolism are pyruvate, oxaloacetate, alpha-ketoglutarate, succinyl-CoA, fumarate, acetyl-CoA, and acetoacetyl-CoA. These intermediates are crucial in metabolic pathways, either entering the citric acid cycle or leading to the production of glucose or ketone bodies. Each intermediate is associated with specific amino acids, which are broken down to contribute to energy production and metabolic balance.