Section 10 2 Review Rna Structure Answer Key

Learning Objectives

By the end of this department, you volition be able to:

• Depict the biochemical structure of ribonucleotides
• Describe the similarities and differences between RNA and DNA
• Describe the functions of the 3 chief types of RNA used in poly peptide synthesis
• Explain how RNA tin can serve every bit hereditary data

Structurally speaking, ribonucleic acrid (RNA), is quite like to DNA. However, whereas DNA molecules are typically long and double stranded, RNA molecules are much shorter and are typically single stranded. RNA molecules perform a variety of roles in the cell but are mainly involved in the process of protein synthesis (translation) and its regulation.

RNA Structure

RNA is typically single stranded and is made of ribonucleotides that are linked by phosphodiester bonds. A ribonucleotide in the RNA chain contains ribose (the pentose sugar), one of the four nitrogenous bases (A, U, One thousand, and C), and a phosphate group. The subtle structural deviation between the sugars gives Deoxyribonucleic acid added stability, making Dna more suitable for storage of genetic data, whereas the relative instability of RNA makes it more suitable for its more curt-term functions. The RNA-specific pyrimidine uracil forms a complementary base pair with adenine and is used instead of the thymine used in DNA. Fifty-fifty though RNA is single stranded, most types of RNA molecules show extensive intramolecular base pairing between complementary sequences within the RNA strand, creating a predictable 3-dimensional construction essential for their role (Figure ten.20 and Figure ten.21).

Figure 10.xx (a) Ribonucleotides comprise the pentose sugar ribose instead of the deoxyribose constitute in deoxyribonucleotides. (b) RNA contains the pyrimidine uracil in place of thymine found in Deoxyribonucleic acid.

Figure 10.21 (a) Dna is typically double stranded, whereas RNA is typically single stranded. (b) Although it is single stranded, RNA can fold upon itself, with the folds stabilized by brusk areas of complementary base pairing within the molecule, forming a three-dimensional structure.

Check Your Agreement

• How does the structure of RNA differ from the construction of DNA?

Functions of RNA in Protein Synthesis

Cells access the information stored in DNA by creating RNA to directly the synthesis of proteins through the process of translation. Proteins within a cell have many functions, including building cellular structures and serving as enzyme catalysts for cellular chemical reactions that requite cells their specific characteristics. The 3 main types of RNA directly involved in protein synthesis are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).

In 1961, French scientists François Jacob and Jacques Monod hypothesized the being of an intermediary between DNA and its poly peptide products, which they called messenger RNA.^sixteen Evidence supporting their hypothesis was gathered presently afterwards showing that data from DNA is transmitted to the ribosome for poly peptide synthesis using mRNA. If DNA serves as the consummate library of cellular information, mRNA serves as a photocopy of specific information needed at a item bespeak in time that serves as the instructions to make a protein.

The mRNA carries the message from the DNA, which controls all of the cellular activities in a prison cell. If a cell requires a certain protein to be synthesized, the gene for this product is "turned on" and the mRNA is synthesized through the process of transcription (encounter RNA Transcription). The mRNA then interacts with ribosomes and other cellular machinery (Effigy 10.22) to direct the synthesis of the protein it encodes during the process of translation (come across Protein Synthesis). mRNA is relatively unstable and short-lived in the cell, peculiarly in prokaryotic cells, ensuring that proteins are only fabricated when needed.

Figure ten.22 A generalized analogy of how mRNA and tRNA are used in protein synthesis inside a prison cell.

rRNA and tRNA are stable types of RNA. In prokaryotes and eukaryotes, tRNA and rRNA are encoded in the Dna, and so copied into long RNA molecules that are cutting to release smaller fragments containing the private mature RNA species. In eukaryotes, synthesis, cut, and assembly of rRNA into ribosomes takes place in the nucleolus region of the nucleus, but these activities occur in the cytoplasm of prokaryotes. Neither of these types of RNA carries instructions to directly the synthesis of a polypeptide, but they play other of import roles in protein synthesis.

Ribosomes are composed of rRNA and protein. Every bit its proper name suggests, rRNA is a major constituent of ribosomes, composing up to about threescore% of the ribosome by mass and providing the location where the mRNA binds. The rRNA ensures the proper alignment of the mRNA, tRNA, and the ribosomes; the rRNA of the ribosome also has an enzymatic activity (peptidyl transferase) and catalyzes the formation of the peptide bonds between two aligned amino acids during protein synthesis. Although rRNA had long been thought to serve primarily a structural role, its catalytic function within the ribosome was proven in 2000.¹⁷ Scientists in the laboratories of Thomas Steitz (1940–) and Peter Moore (1939–) at Yale Academy were able to crystallize the ribosome structure from Haloarcula marismortui, a halophilic archaeon isolated from the Dead Sea. Because of the importance of this work, Steitz shared the 2009 Nobel Prize in Chemical science with other scientists who made meaning contributions to the understanding of ribosome structure.

Transfer RNA is the third chief type of RNA and one of the smallest, usually only lxx–90 nucleotides long. It carries the right amino acid to the site of protein synthesis in the ribosome. It is the base pairing betwixt the tRNA and mRNA that allows for the correct amino acrid to exist inserted in the polypeptide chain being synthesized (Effigy ten.23). Any mutations in the tRNA or rRNA can upshot in global problems for the cell because both are necessary for proper poly peptide synthesis (Tabular array 10.1).

Figure 10.23 A tRNA molecule is a single-stranded molecule that exhibits meaning intracellular base of operations pairing, giving it its characteristic three-dimensional shape.

Structure and Function of RNA
	mRNA	rRNA	tRNA
Construction	Short, unstable, single-stranded RNA corresponding to a gene encoded within Deoxyribonucleic acid	Longer, stable RNA molecules composing 60% of ribosome'southward mass	Short (seventy-90 nucleotides), stable RNA with extensive intramolecular base pairing; contains an amino acid binding site and an mRNA binding site
Part	Serves as intermediary between DNA and protein; used by ribosome to direct synthesis of protein information technology encodes	Ensures the proper alignment of mRNA, tRNA, and ribosome during protein synthesis; catalyzes peptide bond formation between amino acids	Carries the right amino acrid to the site of protein synthesis in the ribosome

Table 10.ane

Check Your Understanding

• What are the functions of the three major types of RNA molecules involved in poly peptide synthesis?

RNA as Hereditary Data

Although RNA does not serve as the hereditary data in most cells, RNA does hold this function for many viruses that do non contain DNA. Thus, RNA clearly does have the additional capacity to serve equally genetic data. Although RNA is typically single stranded within cells, there is pregnant diversity in viruses. Rhinoviruses, which cause the cold; flu viruses; and the Ebola virus are unmarried-stranded RNA viruses. Rotaviruses, which cause severe gastroenteritis in children and other immunocompromised individuals, are examples of double-stranded RNA viruses. Considering double-stranded RNA is uncommon in eukaryotic cells, its presence serves every bit an indicator of viral infection. The implications for a virus having an RNA genome instead of a DNA genome are discussed in more than detail in Viruses.

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Source: https://openstax.org/books/microbiology/pages/10-3-structure-and-function-of-rna

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