Nucleoside and Nucleotide Formation - Online Tutor, Practice Problems & Exam Prep

Nucleosides form when a ribose or deoxyribose sugar creates a glycosidic bond with a nitrogenous base through a condensation reaction, losing water. Nucleotides consist of a nucleoside linked to a phosphate group at the 5' carbon. This process involves the bonding of the phosphate's oxygen to the sugar, completing the nucleotide structure. Understanding these formations is crucial for grasping nucleic acid synthesis and function in biological systems.

Nucleoside and Nucleotide Formation Concept 1

Now when it comes to nucleoside formation, we're going to say that our sugar and base form a glycosidic bond between the anomeric carbon, which is carbon number 1 of a sugar, and the nitrogen of our nitrogenous base. If we take a look here, we're going to say this sugar has an OH group on Carbon number 2. So this means that this represents a ribose sugar. Here, it's reacting with our nitrogenous base. Based on the memory tools that we learned from our previous topic, we know that this nitrogenous base would represent uracil. Now, here what's going to happen is we're going to have the anomeric carbon, this carbon here with its OH interacting with the hydrogen of this nitrogenous base. So, we're going to see that this represents a condensation reaction type reaction, where we're going to lose water. So just think of it like this, we have this OH, we have this H, we're going to lose water, that's gone away, but we need to basically replenish the bonds that we lost. Carbon lost the bond to an OH, nitrogen lost the bond to an H. So, they're going to bond to each other. Doing that helps us to create our glycosidic bond. And what do we have at the end? Well, we have a pentose sugar or pentose ring here, and we have our nitrogenous base. Remember, those two components help to make a nucleoside. And then here goes the water that we lost.

We come down here, what's the difference now? Well, here we no longer have an OH on carbon number 2, we've lost it. We still have an H there that's invisible, remember? Carbon still wants to make 4 bonds. Because we lost an oxygen, this represents a 2-deoxyribose sugar. And then, here, we're looking at this purine, and we know that this purine, based on the memory tools that we've learned earlier, this sugar here, well, this nitrogenous base here represents adenine. Again, think of it as a condensation reaction where we lose H, N, and OH in the form of water. And carbon and nitrogen now, bond to each other. So, we make our glycosidic bond right here. Again, we have our pentose ring with an nitrogenous base. So, again, we've made a nucleoside. So, just remember, this basically is what we deal with when it comes to nucleoside formation where we have the anomeric carbon interac... Environment remains undefined.

Nucleoside and Nucleotide Formation Concept 2

Now remember, the three components that make a nucleotide are a phosphate group, a pentose ring, and a nitrogenous base. Here, we're going to say that nucleotide formation occurs when we have a phosphate group binding to carbon number 5, so 5′ of a nucleoside. Here, we have our nucleoside, which is our pentose ring with our nitrogenous base, and here we have our phosphate group. We're going to bring in our phosphate group and connect the oxygen of the phosphate to this carbon 5′. Carbon needs to make four bonds; it's making one to this oxygen, one to carbon 4, one to this hydrogen, so it needs one more. So, this is actually a CH₂ group. Here, what do we have? We have our phosphate group, our pentose ring, and our nitrogenous base. So, at the end, we have our nucleotide that has been formed. Remember, we've learned about the components of nucleosides and nucleotides earlier, but now we're just trying to see how they form these different types of chemical bonds to create their structures. Right. So keep that in mind when we're talking about nucleoside formation, or in this case, nucleotide formation.

Nucleoside and Nucleotide Formation Example 1

Here in this question, it says, draw a nucleotide formed from the following sugar and base. Alright. So pay attention. It's not saying nucleoside, it's saying nucleotide. That means that we need to bring in a third component at the end, which is our phosphate group. Now, first, let's make our nucleoside, which is just our sugar and base connecting. To do that, we have our carbon 1' here, interacting with the NH group of our nitrogenous base. Remember what's going to happen here is we're going to lose water because it's a condensation. So these will be lost. So what we'll get here is, here is our ring still. Here's the OH that's attached to it. Now we're going to have our glycosidic bond being formed; here goes our nitrogen. That's still part of this ring. And we have this metal here. And then, this is just our nucleoside right now. We need to draw a nucleotide so we need to bring in our phosphate group. So remember here, we'd still have a CH₂ group. Now, what we're doing is we're bringing in the phosphate group. So I'm going to draw the phosphate group, here goes the oxygen of the phosphate group and that's connected to our phosphorus which is single bonded to these oxygens here and then double bonded to this oxygen here. Well, this will represent the structure of our nucleotide, which again remember is our phosphate group connected to a pentose ring connected to a nitrogenous base.

Draw a nucleoside formed when ribose and cytosine form a glycosidic bond.

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• B.
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• D.

Draw a nucleotide formed when deoxyribose and guanine form a glycosidic bond.

Here it says we need to draw a nucleotide when deoxyribose and guanine form a glycosidic bond. Alright. So, a nucleotide means that we'd also have to incorporate a phosphate group. So, actually, let's draw the deoxyribose sugar with the phosphate group attached. Here we have our pentose ring. Deoxyribose means that carbon number 2, which is this carbon, doesn't have an OH. There's still an OH on carbon 3. We're going to say carbon number 5, which is the CH2 group, is going to be connected to our phosphate group. Equals our phosphate group. And then we need to form our bond, our glycosidic bond, to the nitrogen of the guanine. Remember, guanine here represents a purine, so it's 2 fused rings. So if we drew guanine over here before we connected it, it would look like this. And we'd have our 6-membered ring. So, there goes our guanine. And remember, there was an OH here, and we'd lose this H and this OH through condensation as water. And that carbon and the nitrogen from guanine will connect. So let's show that connection. So there goes the nitrogen we're connected to. It is part of this ring, which is connected to the 6-member ring. So there goes our structure here. So we have our nucleotide which is our phosphate group connected to our pentose sugar in the form of deoxyribose sugar, and then guanine which is our nitrogenous base. So this will be the way we would represent this particular nucleotide.

Here’s what students ask on this topic:

What is the difference between a nucleoside and a nucleotide?

A nucleoside consists of a pentose sugar (either ribose or deoxyribose) bonded to a nitrogenous base via a glycosidic bond. In contrast, a nucleotide is a nucleoside that has one or more phosphate groups attached to the 5' carbon of the sugar. The addition of the phosphate group(s) is what differentiates a nucleotide from a nucleoside. Nucleotides are the building blocks of nucleic acids like DNA and RNA, playing crucial roles in cellular processes such as energy transfer and signal transduction.

How is a glycosidic bond formed in nucleosides?

A glycosidic bond in nucleosides is formed through a condensation reaction between the anomeric carbon (carbon 1) of a pentose sugar and a nitrogen atom of a nitrogenous base. During this reaction, a molecule of water is lost. Specifically, the hydroxyl group (OH) from the sugar and a hydrogen atom (H) from the nitrogenous base combine to form water (H₂O), which is then removed, allowing the carbon and nitrogen to bond directly, creating the glycosidic bond.

What are the components required for nucleotide formation?

The components required for nucleotide formation are a pentose sugar, a nitrogenous base, and a phosphate group. The pentose sugar and nitrogenous base form a nucleoside through a glycosidic bond. Then, a phosphate group attaches to the 5' carbon of the sugar, completing the nucleotide structure. This attachment involves the oxygen of the phosphate group bonding to the 5' carbon, forming a phosphoester bond.

What is the role of condensation reactions in nucleoside and nucleotide formation?

Condensation reactions play a crucial role in both nucleoside and nucleotide formation. In nucleoside formation, a condensation reaction occurs between the anomeric carbon of the sugar and the nitrogen of the nitrogenous base, resulting in the loss of a water molecule and the formation of a glycosidic bond. In nucleotide formation, another condensation reaction occurs when a phosphate group attaches to the 5' carbon of the nucleoside, again resulting in the loss of a water molecule and the formation of a phosphoester bond. These reactions are essential for building the structures of nucleic acids.

How does the structure of ribose differ from deoxyribose in nucleosides?

The primary difference between ribose and deoxyribose in nucleosides is the presence of a hydroxyl group (OH) on the 2' carbon of ribose, whereas deoxyribose has only a hydrogen atom (H) at this position. This difference is crucial because it affects the overall structure and function of the nucleic acids they form. Ribose is found in RNA, making it more reactive and less stable, while deoxyribose is found in DNA, contributing to its stability and resistance to hydrolysis.