Intro to Nucleic Acids - Online Tutor, Practice Problems & Exam Prep

Intro to Nucleic Acids Concept 1

Hey, everyone. Before we talk about nucleic acids, it's important to discuss what a nucleotide is. A nucleotide represents a monomer, or single unit, of a nucleic acid. Here, a nucleic acid is just a polymer of nucleotides that store and encode genetic information. When we talk about nucleotides, we're going to say there are two types: we have DNA and we have RNA. DNA represents deoxyribonucleic acid and RNA represents ribonucleic acid. With DNA, we're going to say that it stores genetic information of cellular organisms. RNA transfers this genetic information from DNA in order to create proteins later on.

Since we have identified these two types of nucleotides, it's important to discuss the components of a nucleotide. However, before we can discuss a nucleotide, we need to talk about its precursor, which is the nucleoside. A nucleoside consists of two things: a pentose sugar and a nitrogenous base. If we take a look here at this structure, before the arrow, on the left side of the arrow, we have our pentose sugar and our nitrogenous base, thus forming a nucleoside. A nucleotide consists of this nucleoside plus a phosphate group. As we follow the arrow towards the right side, we've attached a phosphate group to our setup. So, a nucleotide's three components are a phosphate group, a pentose sugar, and a nitrogenous base. Remember these key terms when discussing nucleotides, nucleosides, and nucleic acids overall.

Intro to Nucleic Acids Concept 2

In this video, we'll talk about RNA nucleotides versus DNA nucleotides. Now here we're going to say that our pentose sugar in RNA is ribose, and when it's DNA, it's 2-deoxyribose. Now, here is some important terminology. When we say deoxy, deoxy just means without oxygen. So if we take a look at the image on the left side, we're going to say that this here will represent our RNA nucleotide. We're going to say here that our RNA nucleotide has a phosphate group. It has its pentose ring, and it has its nitrogenous base. Remember, those three components make up a nucleotide. Here, though, because it's RNA, the pentose ring is a ribose sugar. Because it's a ribose sugar, it has an OH group right here. When we talk about DNA, so here we're looking at the DNA nucleotide. It's a nucleotide, so it still has the 3 components that make it up, which is a phosphate group, a ring, a pentose ring, as well as a nitrogenous base. But because it's DNA involved, we're not going to have an OH here, we're going to have just an H with lost Oxygen. So that's why we're going to call this a deoxyribose sugar. Right? So just remember, these are the key differences between DNA and RNA.

Intro to Nucleic Acids

In this example question, it says, select the correct statement describing nucleotides. Here, the sugar in DNA has an extra OH group than the sugar in RNA. Now remember, deoxyribose sugar is indicative of DNA. That means we've lost an oxygen. So we wouldn't have an extra OH group. All nucleotides contain a nitrogenous base. This is true. Remember, nucleotides have 3 components: a phosphate group, our pentose ring, as well as a nitrogenous base. So this is true. Here, the sugar in DNA contains one less carbonyl group than the sugar in RNA. So remember, what's the difference between RNA and DNA? We have one less oxygen in DNA. That's why deoxyribose sugar is involved. Here, not all nucleotides contain ribose sugar. This is not true. DNA represents a sugar or it represents a nucleotide, actually. And DNA does not have a ribose sugar. It has a deoxyribose sugar because it has one less oxygen. So here, the only statement that's true is option B. All nucleotides contain a nitrogenous base.