10.3 Structure and Function of RNA
4 min read•june 18, 2024
is the versatile cousin of , playing crucial roles in gene expression and cellular function. From messenger RNA carrying genetic instructions to transfer RNA delivering amino acids, RNA molecules come in various forms with diverse responsibilities.
RNA's unique structure allows it to fold into complex shapes, enabling catalytic and regulatory functions. Unlike DNA, RNA can serve as genetic material for some viruses and may have been the original basis for life in the "RNA world" hypothesis.
RNA Structure and Function
Structure and role of ribonucleotides
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- serve as the building blocks of RNA molecules
- Consist of three components: a , a pentose sugar (), and a
- Nitrogenous bases in RNA include (A), (G), (C), and (U) which replaces thymine (T) found in DNA
- Ribose sugar contains an additional hydroxyl group (-OH) at the 2' position compared to deoxyribose in DNA enabling RNA to fold into various functional shapes
- are linked together by forming a single-stranded RNA molecule with a 5' to 3' directionality
- Bonds form between the 3' hydroxyl group of one ribonucleotide and the 5' phosphate group of the next
- RNA can form secondary structures through base pairing interactions
- Adenine (A) pairs with (U) via two hydrogen bonds while guanine (G) pairs with cytosine (C) via three hydrogen bonds
- Base pairing allows RNA to fold into various functional shapes such as and
- RNA molecules can also form complex tertiary structures through additional interactions between different regions of the molecule
RNA vs DNA: Key features
- Similarities between RNA and DNA:
- Both are composed of monomers containing the nitrogenous bases adenine (A), guanine (G), and cytosine (C)
- Both have a with 5' to 3' directionality
- Differences between RNA and DNA:
- Sugar component: RNA contains ribose while DNA contains deoxyribose
- Nitrogenous bases: RNA uses uracil (U) instead of thymine (T) found in DNA
- Strand number: RNA is typically single-stranded while DNA is double-stranded
- Stability: RNA is less stable than DNA due to the presence of the reactive 2' hydroxyl group
- Function: DNA primarily serves as the genetic material while RNA has diverse roles in gene expression (mRNA), amino acid delivery (tRNA), and catalysis ()
Functions of RNA types
- carries genetic information from DNA to for
- Produced through where synthesizes a complementary RNA strand from a DNA template
- Consists of a , coding region containing that specify amino acids, and 3'
- Undergoes to remove introns and join exons before
- acts as adapter molecules that translate the genetic code from mRNA into amino acids
- Contain an loop that base pairs with the complementary codon on mRNA
- Undergo where they are "charged" with their corresponding amino acids by
- serves as the main structural and catalytic component of
- Ribosomes are composed of a large (50S) and small (30S) subunit in prokaryotes, each containing specific rRNAs (23S and 16S respectively)
- rRNAs facilitate ribosome assembly and catalyze formation during protein synthesis
RNA as genetic material
- Some viruses use RNA as their genetic material instead of DNA
- Single-stranded RNA viruses (, , ): genome serves as both genetic material and mRNA for protein synthesis
- viruses (): genome segments are transcribed into mRNA for protein synthesis
- (HIV): single-stranded RNA genome is into DNA, integrates into host genome, and is transcribed to produce viral proteins and new RNA genomes
- proposes that early life relied on RNA as both genetic material and catalytic molecule before DNA and proteins emerged
- RNA can store genetic information and catalyze chemical reactions supporting its crucial role in the origin and evolution of life
Regulatory and Catalytic RNA Functions
- (ribozymes) can perform enzymatic functions, such as self-splicing introns and formation in ribosomes
- (RNAi) is a regulatory mechanism that uses small RNA molecules to silence gene expression
- Small nuclear RNAs (snRNAs) play a crucial role in pre-mRNA splicing as components of the spliceosome
- MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression by binding to target mRNAs and inhibiting translation or promoting degradation
Key Terms to Review (56)
5' Cap: The 5' cap is a modified guanine nucleotide added to the 5' end of a mature eukaryotic messenger RNA (mRNA) molecule. It plays a crucial role in the structure and function of RNA, as well as in the process of protein synthesis (translation).
Adenine: Adenine is a nitrogenous base that is one of the five main nucleobases found in the nucleic acids DNA and RNA. It is a crucial component of these biomolecules, playing a vital role in their structure and function.
Aminoacyl-tRNA Synthetases: Aminoacyl-tRNA synthetases are a class of enzymes responsible for attaching specific amino acids to their corresponding transfer RNA (tRNA) molecules. These enzymes play a crucial role in the process of protein synthesis by ensuring the accurate pairing of amino acids with their cognate tRNA, which is essential for the proper translation of genetic information into functional proteins.
Aminoacylation: Aminoacylation is the process by which an amino acid is covalently attached to its corresponding transfer RNA (tRNA) molecule. This critical step is essential for protein synthesis, as it prepares the amino acid to be incorporated into the growing polypeptide chain during translation.
Anticodon: The anticodon is a sequence of three nucleotides on a transfer RNA (tRNA) molecule that is complementary to the codon on a messenger RNA (mRNA) molecule. It plays a crucial role in the translation process, where it facilitates the incorporation of the correct amino acid into the growing polypeptide chain.
Catalytic RNA: Catalytic RNA, also known as ribozymes, are RNA molecules that can act as enzymes, catalyzing specific chemical reactions without the need for protein cofactors. These self-cleaving or self-splicing RNAs play important roles in various biological processes, particularly in the structure and function of RNA within the cell.
Codons: Codons are the fundamental units of the genetic code, consisting of three consecutive nucleotides in a messenger RNA (mRNA) molecule that specify the amino acid to be incorporated into a polypeptide chain during protein synthesis. Codons are essential for the translation of genetic information into functional proteins, a critical process in the structure and function of RNA as well as the overall functions of genetic material.
Cytosine: Cytosine is one of the four primary nitrogenous bases found in nucleic acids, specifically DNA and RNA. It is a pyrimidine derivative that plays a crucial role in the structure and function of these genetic materials.
DNA: DNA (Deoxyribonucleic Acid) is the hereditary material in almost all living organisms, carrying genetic information essential for growth, development, and reproduction. It consists of two strands forming a double helix structure.
Double-stranded RNA: Double-stranded RNA (dsRNA) consists of two complementary strands of RNA that form a helical structure. It plays crucial roles in cellular processes, including antiviral defense and gene silencing mechanisms.
Guanine: Guanine is a purine nucleobase that is one of the four main chemical building blocks of DNA and RNA. It is a key component in the genetic code and plays a vital role in the structure and function of nucleic acids.
Hairpin Loops: Hairpin loops are secondary structures that form in single-stranded RNA molecules when complementary base pairs within the same strand interact, creating a U-shaped loop. These structures are an important feature in the overall folding and function of RNA.
Influenza Virus: The influenza virus is a type of RNA virus that causes the contagious respiratory illness known as the flu. It is a member of the Orthomyxoviridae family and is a significant public health concern due to its ability to cause seasonal epidemics and occasional global pandemics.
Messenger RNA (mRNA): Messenger RNA (mRNA) is a type of RNA that carries genetic information from DNA to the ribosome, where it serves as a template for protein synthesis. mRNA sequences are transcribed from DNA and translated into amino acid sequences.
MicroRNA (miRNA): microRNA (miRNA) are small, non-coding RNA molecules that play a crucial role in regulating gene expression by targeting and binding to messenger RNA (mRNA) molecules, leading to their degradation or translational repression. These tiny RNA fragments are essential for various cellular processes and are closely linked to the structure and function of RNA in living organisms.
Nitrogenous Base: A nitrogenous base is a type of organic compound that contains at least one nitrogen atom and is a key structural component of nucleic acids, such as DNA and RNA. These bases play a crucial role in the storage and transmission of genetic information within living organisms.
Nucleic Acids: Nucleic acids are macromolecules that serve as the genetic material in living organisms, carrying the instructions necessary for cellular function and replication. They are composed of monomeric units called nucleotides and play a central role in the storage, transmission, and expression of genetic information.
Nucleotide: A nucleotide is the fundamental building block of nucleic acids, such as DNA and RNA. It consists of a nitrogenous base, a pentose sugar, and a phosphate group. Nucleotides play a crucial role in various biological processes, including energy production, cellular signaling, and the storage and transmission of genetic information.
Peptide bond: A peptide bond is a covalent chemical bond formed between two amino acid molecules. It occurs when the carboxyl group of one amino acid reacts with the amino group of another, releasing a molecule of water.
Peptide Bond: A peptide bond is a covalent chemical bond that is formed between the carboxyl group of one amino acid and the amino group of another amino acid, resulting in the creation of a polypeptide chain. This bond is crucial for the structure and function of proteins, which are essential macromolecules in living organisms.
Peptidyl transferase: Peptidyl transferase is an enzyme that forms peptide bonds between adjacent amino acids during protein synthesis. It is a critical component of the ribosome's large subunit.
Peter Moore: Peter Moore is a molecular biologist known for his research on the structure and function of ribosomal RNA (rRNA) and its role in protein synthesis. His work has significantly advanced our understanding of rRNA's three-dimensional structure.
Phosphate Group: A phosphate group is a molecular structure consisting of a central phosphorus atom covalently bonded to four oxygen atoms. This functional group is ubiquitous in biological systems, playing crucial roles in the structure and function of lipids, DNA, and RNA.
Phosphodiester Bonds: Phosphodiester bonds are covalent chemical bonds that link the phosphate group of one nucleotide to the sugar (deoxyribose or ribose) of the next nucleotide, forming the backbone of nucleic acids like DNA and RNA. These bonds are essential for the structural integrity and function of these genetic molecules.
Poliovirus: Poliovirus is a highly contagious virus that primarily infects the gastrointestinal tract and can lead to the debilitating disease polio. It is a member of the Picornaviridae family and is the causative agent of the viral infection known as poliomyelitis.
Poly(A) tail: The poly(A) tail is a sequence of adenine (A) nucleotides added to the 3' end of a mature eukaryotic messenger RNA (mRNA) molecule. This post-transcriptional modification is crucial for the stability, localization, and translation of the mRNA transcript.
Protein synthesis: Protein synthesis is the biological process by which cells generate new proteins. It involves transcription of DNA into mRNA and translation of mRNA into a polypeptide chain.
Retroviruses: Retroviruses are a unique class of viruses that use RNA as their genetic material and employ a reverse transcriptase enzyme to convert their RNA into DNA, which is then integrated into the host cell's genome. This distinctive life cycle and genetic structure allows retroviruses to persistently infect their hosts and utilize the cellular machinery for their own replication.
Reverse Transcribed: Reverse transcription is the process by which a single-stranded RNA molecule is used as a template to synthesize a complementary DNA (cDNA) strand. This process is the reverse of the typical DNA-to-RNA transcription, hence the term 'reverse transcribed.'
Ribonucleic acid (RNA): Ribonucleic acid (RNA) is a nucleic acid that plays crucial roles in coding, decoding, regulation, and expression of genes. It is typically single-stranded and composed of ribonucleotides.
Ribonucleotides: Ribonucleotides are the basic building blocks of RNA, consisting of a ribose sugar, a phosphate group, and a nitrogenous base. They play essential roles in coding, decoding, regulation, and expression of genes.
Ribonucleotides: Ribonucleotides are the building blocks of ribonucleic acid (RNA), which is a nucleic acid that plays a crucial role in the storage and expression of genetic information within cells. Ribonucleotides consist of a ribose sugar, a nitrogenous base, and a phosphate group, and they are the fundamental units that make up the structure and function of RNA.
Ribose: Ribose is a type of monosaccharide, a simple sugar that serves as the structural backbone of ribonucleic acid (RNA). It is an essential component in the structure and function of RNA, which plays a crucial role in various biological processes, including the storage and expression of genetic information.
Ribosomal RNA (rRNA): Ribosomal RNA (rRNA) is a type of RNA that, along with proteins, makes up the ribosomes. Ribosomes are the cellular structures where protein synthesis occurs.
Ribosomes: Ribosomes are molecular machines within cells that synthesize proteins by translating messenger RNA (mRNA) into polypeptide chains. They are composed of ribosomal RNA (rRNA) and proteins, and they exist in both prokaryotic and eukaryotic cells.
Ribosomes: Ribosomes are the cellular organelles responsible for the synthesis of proteins, which are essential for the structure, function, and regulation of biological processes within cells. They are found in both prokaryotic and eukaryotic cells, playing a crucial role in the Foundations of Modern Cell Theory, the Unique Characteristics of Eukaryotic Cells, the Structure and Function of RNA, and the Functions of Genetic Material.
Ribozymes: Ribozymes are RNA molecules that have the ability to catalyze specific chemical reactions, much like enzymes. They are capable of acting as biological catalysts, playing a crucial role in various cellular processes related to the structure and function of RNA.
RNA: RNA, or ribonucleic acid, is a crucial biological macromolecule that plays a vital role in various cellular processes, including the storage and expression of genetic information, protein synthesis, and gene regulation. As a nucleic acid, RNA is closely related to DNA, sharing many structural and functional similarities, yet also exhibiting distinct characteristics that make it a unique and essential component of living organisms.
RNA Interference: RNA interference (RNAi) is a biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. This mechanism is used by cells to regulate gene expression and defend against viral infections.
RNA Polymerase: RNA polymerase is the enzyme responsible for the transcription of genetic information from DNA into RNA, a crucial step in the central dogma of molecular biology. This enzyme is essential for the synthesis of various types of RNA, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA), which are all vital for the expression and regulation of genes.
RNA Splicing: RNA splicing is the process by which introns (non-coding regions) are removed from a precursor messenger RNA (pre-mRNA) molecule, and the remaining exons (coding regions) are joined together to form a mature, functional mRNA molecule. This process is essential for the proper expression of genes in eukaryotic organisms, including those involved in the topics of viroids, virusoids, and the structure and function of RNA.
RNA World Hypothesis: The RNA World Hypothesis proposes that in the early stages of life on Earth, RNA molecules were the primary carriers of genetic information and catalysts for essential biological processes, before the emergence of DNA and proteins. This hypothesis suggests that RNA, with its ability to both store genetic information and catalyze chemical reactions, was the predominant form of life in the primordial environment.
Rotavirus: Rotavirus is a genus of double-stranded RNA viruses that are a leading cause of severe gastroenteritis in infants and young children worldwide. These viruses primarily infect the gastrointestinal tract and are responsible for a significant portion of viral infections affecting the digestive system.
SARS-CoV-2: SARS-CoV-2 is the virus that causes the disease COVID-19. It is a novel coronavirus that emerged in late 2019 and has since led to a global pandemic, significantly impacting public health worldwide.
Secondary Structure: Secondary structure refers to the local, regular, and repeating three-dimensional (3D) structure of biomolecules, particularly proteins and RNA. It describes the spatial arrangement of the backbone and side chains within a molecule, which is stabilized by hydrogen bonding and other non-covalent interactions.
Small Nuclear RNA (snRNA): Small nuclear RNAs (snRNAs) are a class of small, non-coding RNAs found in the nucleus of eukaryotic cells. They play a crucial role in the processing and splicing of messenger RNA (mRNA) by forming the small nuclear ribonucleoprotein (snRNP) complexes that make up the spliceosome, a key component of the RNA splicing machinery.
Steitz: Steitz refers to Thomas A. Steitz, an American biochemist renowned for his work in elucidating the structure and function of the ribosome, a critical component in RNA translation. His research has greatly contributed to our understanding of how genetic information is translated into proteins.
Stem-loops: Stem-loops, also known as hairpin loops, are secondary structures formed in single-stranded RNA molecules. They consist of a double-stranded stem region and a single-stranded loop region, creating a characteristic hairpin-like shape that is essential for various biological functions.
Sugar-Phosphate Backbone: The sugar-phosphate backbone is the structural framework that forms the backbone of DNA and RNA molecules. It is composed of alternating sugar (deoxyribose or ribose) and phosphate groups, which provide the structural support and directionality for the nucleic acid strands.
Tertiary Structure: Tertiary structure refers to the three-dimensional folding and organization of a protein or RNA molecule. It is the highest level of structural complexity and is essential for the proper function of these biomolecules.
Transcription: Transcription is the process by which a segment of DNA is copied into RNA by the enzyme RNA polymerase. It is the first step in gene expression, allowing genetic information to be transcribed for protein synthesis.
Transcription: Transcription is the process by which the genetic information encoded in a DNA sequence is copied into a complementary RNA molecule, which then serves as a template for the synthesis of proteins. It is a fundamental step in the central dogma of molecular biology, where DNA is transcribed into RNA, which is then translated into proteins.
Transfer RNA (tRNA): Transfer RNA (tRNA) is a type of RNA molecule that helps decode mRNA sequences into proteins. It carries amino acids to the ribosome, matching them with the appropriate codons on the mRNA strand during translation.
Translation: Translation is the process by which ribosomes synthesize proteins using mRNA as a template. It involves decoding the genetic information contained in mRNA to produce a specific polypeptide chain.
Uracil: Uracil is a nitrogenous base found in RNA, replacing thymine which is found in DNA. It pairs with adenine during the formation of RNA strands.
Uracil: Uracil is a pyrimidine nucleobase that is a key component of ribonucleic acid (RNA). It is one of the four primary nucleobases found in RNA, along with adenine, guanine, and cytosine. Uracil plays crucial roles in the structure and function of RNA, as well as in the process of RNA transcription.