Biology Chapter 4: Nucleic Acids

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Questions and Answers

Describe the primary, secondary, tertiary, and quaternary structures of RNA, and explain in what ways RNA differs from DNA.

Primary structure: sugar-phosphate backbone with a sequence of 4 nitrogenous bases (A, U, C, G). Secondary structure: complementary base pairing that forms hairpin loops. Tertiary structure: distinctive three-dimensional shapes of RNA. Quaternary structure: none. Difference: DNA has thymine, while RNA has uracil.

Explain how the secondary structure of DNA allows organisms to store and copy information.

DNA stores information in genes that can replicate by using each strand as a template through complementary base pairing.

Explain why RNA, and not DNA, was probably the first self-replicating molecule.

RNA can store information and catalyze its own polymerization, allowing self-replication.

What are nucleic acids made of?

Nucleic acids are polymers made of monomers called nucleotides. Signup and view all the answers

What are monomers and what are polymers?

A monomer is a small molecule that can bind to others to form a macromolecule. A polymer is a long molecule made of repeating monomers. Signup and view all the answers

What are nitrogenous bases? What are the purines and pyrimidines?

Nitrogenous bases are C, U, T, G, and A. Purines are guanine and adenine; pyrimidines are cytosine, uracil (RNA), and thymine (DNA). Signup and view all the answers

Which nitrogenous bases are associated with DNA and which with RNA?

DNA: adenine, thymine, guanine, cytosine. RNA: adenine, uracil, guanine, cytosine. Signup and view all the answers

What is ribose and what is a ribonucleotide?

Ribose is a sugar found in RNA. Ribonucleotides are the monomers found in RNA. Signup and view all the answers

What is deoxyribose and what is a deoxyribonucleotide?

Deoxyribose is a sugar found in DNA. Deoxyribonucleotides are the monomers found in DNA. Signup and view all the answers

Describe the polymerization process for DNA.

Nucleotides polymerize via phosphodiester linkages formed between the hydroxyl group of one nucleotide's sugar and the phosphate group of another. Signup and view all the answers

What are activated deoxyribonucleotides and how do they fuel the polymerization of DNA?

Activated deoxyribonucleotides have 2 phosphate groups added, raising their potential energy and enabling polymerization when phosphates are removed. Signup and view all the answers

Who was involved in the discovery of DNA's secondary structure?

James Watson and Francis Crick discovered the antiparallel configuration of DNA and its double helix structure. Signup and view all the answers

How would you describe DNA's primary structure? Its secondary structure?

DNA's primary structure is a linear sequence of nucleotides linked by phosphodiester bonds; its secondary structure consists of complementary base pairs forming a double helix. Signup and view all the answers

What do antiparallel strands mean?

Antiparallel strands mean two DNA strands run in opposite directions, one in the 5'->3' direction and the other in the 3'->5' direction. Signup and view all the answers

How might DNA serve to store information?

DNA stores information in sequences of four bases that can create templates for exact copies. Signup and view all the answers

How might have RNA been involved in chemical evolution?

RNA could replicate itself, providing templates and catalyzing polymerization reactions essential for early life forms. Signup and view all the answers

What is a template strand? A complementary strand?

A template strand is the original strand of DNA, allowing free deoxyribonucleotides to form hydrogen bonds with its complementary bases to create a new strand. Signup and view all the answers

List the differences between DNA and RNA.

DNA has a double helix shape and pairs bases on two antiparallel strands; RNA pairs bases on a single strand in a hairpin loop. DNA has thymine, while RNA has uracil. Signup and view all the answers

Draw a nucleotide and label the three basic parts.

Three parts: phosphate group, 5-carbon sugar, nitrogenous base. Signup and view all the answers

Study Notes

Structures of RNA and DNA

Primary structure consists of a sugar-phosphate backbone formed by phosphodiester linkages and a sequence of nitrogenous bases (DNA: ATCG; RNA: AUCG).
RNA has Uracil (U) instead of Thymine (T) which is found in DNA.
Secondary structure involves base pairing: RNA forms hairpin loops with hydrogen bonds on the same strand; DNA forms a double helix with antiparallel strands.
Tertiary structure in RNA leads to complex three-dimensional shapes; DNA lacks a tertiary structure.
Both RNA and DNA do not have quaternary structure.

Function of DNA Secondary Structure

DNA's secondary structure allows organisms to store information in genes, similar to "words" that instruct protein synthesis.
Each DNA strand serves as a template for replication through complementary base pairing.

RNA as a Self-Replicating Molecule

RNA can store information and catalyze its polymerization, enabling self-replication.
Ribose became the predominant sugar during early chemical evolution.

Composition of Nucleic Acids

Nucleic acids are polymers made of monomer units called nucleotides, which consist of a phosphate group, a 5-carbon sugar, and a nitrogenous base.

Monomers and Polymers

Monomers are small molecules that bond covalently to form larger macromolecules.
Polymers are larger molecules composed of repeating monomer units; major biological polymers include proteins, nucleic acids, and polysaccharides.

Nitrogenous Bases

Nitrogenous bases include Adenine (A), Guanine (G), Cytosine (C), Thymine (T), and Uracil (U).
Purines: Adenine and Guanine; Pyrimidines: Cytosine, Uracil (present in RNA), and Thymine (present in DNA).

Nucleotide Components

Ribose is the sugar component in RNA; ribonucleotides are the monomers of RNA.
Deoxyribose is the sugar in DNA; deoxyribonucleotides are the monomers of DNA.

Polymerization Process of DNA

DNA polymerization occurs through phosphodiester linkages, forming bonds between nucleotides.
The forward reaction connects the 5' carbon of one nucleotide to the 3' carbon of another; the reverse reaction is 3' to 5'.
This condensation reaction links nucleotides during DNA formation.

Activated Deoxyribonucleotides

Activated deoxyribonucleotides have two phosphate groups added, increasing their potential energy.
Energy is released upon hydrolysis; phosphate groups create repulsive forces that facilitate bond formation.

Discovery of DNA's Structure

James Watson and Francis Crick identified DNA's double helix structure and antiparallel strands.
Key features include the hydrophilic sugar-phosphate backbone, base pairing (A-T, G-C), hydrogen bond differences (A-T: 2 bonds, C-G: 3 bonds), and the presence of major and minor grooves.

DNA Primary and Secondary Structure

Primary structure consists of a linear nucleotide sequence linked by phosphodiester bonds, carrying genetic information.
Secondary structure forms a double helix, allowing for stability and base pairing.

Antiparallel Strands and Directionality

DNA strands run in opposite directions (5' to 3' and 3' to 5'), crucial for replication and transcription.

DNA in Information Storage

Biological information is encoded in sequences of four bases (A, T, C, G) along a sugar-phosphate backbone.
Unzipped DNA provides templates for synthesis of exact copies.

RNA and Chemical Evolution

RNA likely played a key role in early life as a self-replicator capable of providing templates and catalyzing polymerization.

Template and Complementary Strands

The template strand serves as the original DNA strand, guiding the formation of a complementary strand through base pairing and phosphodiester linkage.

Key Differences Between DNA and RNA

DNA: double helix, two antiparallel strands, Thymine (T).
RNA: single strand, hairpin loop shape, Uracil (U), possesses tertiary structure and can catalyze reactions.

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Test your knowledge with this flashcard quiz on the primary, secondary, tertiary, and quaternary structures of RNA, and learn how RNA differs from DNA. Perfect for students studying molecular biology and genetics.