RNA Study Guide

Youtube Guide:

Lesson Objectives

  • Understand the importance and structure of an RNA molecule.
  • Understand the functions of the three different types of RNA in a cell.

Ribonucleic Acid (RNA)

Let’s start with the basics. You’ve probably heard of DNA before (deoxyribonucleic acid). It carries our genetic code–the textbook from which all the information we need to grow, survive, and reproduce originates. DNA is found in the nucleus in the form of either chromatin or chromosomes. It’s composed of a sequence of nucleotides that link together into one long double-stranded molecule. The order of these nucleotide bases determines our genetic blueprint, kind of like how the order we put the letters of the alphabet in determines our words.

Thinking about DNA in terms of language is actually pretty useful. It has all of our genetic information written down in its own language, but unfortunately, the rest of the cell doesn’t speak it. Seems like a pretty big oversight in terms of communication (who even designed this thing?), but luckily, there’s another molecule in the mix who can help translate: ribonucleic acid, also known as RNA.

RNA and DNA are two of the three most important macromolecules necessary for life. The third one is proteins, which DNA and RNA work together to produce. In the simplest terms possible, DNA makes RNA, and RNA makes proteins. There are three types of RNA involved in protein synthesis: messenger RNA, transfer RNA, and ribosomal RNA. We’ll talk about what they do in a minute after we briefly touch on what makes DNA and RNA different, besides the first letter of their name (LOL) (so funny!) (aren’t we funny?) (tell us we’re funny).

How is DNA Different from RNA?

DNA and RNA are actually pretty similar in terms of both structure and function. They’re both nucleic acids made of nucleotides, and those nucleotides are almost the same, but not quite. DNA uses the bases Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). RNA uses the first three, but instead of thymine it has Uracil (U).

Another distinction is that DNA is made of two strands, while RNA is only made of one. The main difference between them though is that the nucleotides that make up RNA are composed of a nucleobase, a ribose sugar, and a phosphate group, while DNA’s nucleotides are made of a nucleobase, a deoxyribose sugar, and a phosphate group. Other than that, they’re pretty similar, so let’s move on to the different types of RNA.

The Three Types of RNA

Before we got distracted by the last section, we were talking about how RNA has three different forms– messenger RNA, transfer RNA, ribosomal RNA. They each have a special function to help out with the process of protein synthesis, which we’ll briefly go over below.

  • The first step of making proteins is to translate DNA into a message that the rest of the cell can read. This message comes in the form of Messenger RNA (mRNA), which is then transferred from the nucleus to the cytoplasm.

  • Once in the cytoplasm, the small subunit of a ribosome attaches to the mRNA and translates it for the large subunit, which synthesizes a polypeptide chain of amino acids–the base form of a protein. Transfer RNA (tRNA) delivers the amino acids to the ribosomes as they synthesize these chains.

  • Ribosomes are composed of proteins and Ribosomal RNA (rRNA), our final type of RNA. Once the polypeptide chain has been assembled, the ribosome transports it to the rough endoplasmic reticulum, embeds itself into its membrane, and releases the chain so that it can be folded into its final, functional protein form.

trna mrna rrna

💡 Summary

  • DNA is the carrier of our genetic information.

  • RNA translates DNA so that it can be used to create proteins.

  • DNA and RNA are mostly similar, with a few key differences. DNA is double-stranded, while RNA is single-stranded. DNA is composed of the nucleotides A, C, G, and T, while RNA is composed of the nucleotides A, C, G, and U. Lastly, the sugar used in the backbone of RNA is ribose, while the sugar in DNA is deoxyribose.

  • There are three types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

  • Messenger RNA translates DNA and transfers it from the nucleus to the cytoplasm.

  • Once in the cytoplasm, ribosomes use the mRNA to synthesize a string of amino acids called a polypeptide chain. Transfer RNA delivers the amino acids to the ribosome.

  • Ribosomes are composed partially of ribosomal RNA.


1. What is the purpose of tRNA?

Transfer RNA is responsible for delivering amino acids to the ribosome as it synthesizes a polypeptide chain.

2. What is the difference between DNA and RNA?

  • RNA is made of a sugar called ribose. DNA contains a slightly varied sugar called deoxyribose.

  • RNA has the nucleobase named uracil, while DNA contains the nucleobase thymine.

  • DNA is double-stranded, while RNA is composed of a single strand.

3. What is the purpose of rRNA?

Ribosomal RNA, along with proteins, make up the composition of ribosomes, the organelle respomsible for protein synthesis.

4. What is the purpose of mRNA?

DNA is translated into Messenger RNA, which is then transported from the nucleus to the cytoplasm where it delivers instructions to ribosomes for protein synthesis.

5. What do the two subunits of a ribosome do?

The small subunit uses mRNA to provide instructions to the large subunit, which is responsible for building polypeptide chains to synthesize proteins.

6. Why is DNA better genetic material as compared to RNA?

The deoxyribose sugar of the DNA is composed of one less oxygen-containing hydroxyl group. DNA is thus a more stable nucleic acid. RNA contains a ribose sugar, which is more reactive than DNA. Thus DNA is a better genetic material as compared to RNA.

We hope you enjoyed studying this lesson and learned something cool about RNA! Join our Discord community to get any questions you may have answered and to engage with other students just like you! Don’t forget to download our App and check out our awesome VR room for this guide – we promise, it makes studying much more fun 😎


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