Nucleotides and Nucleic Acids Overview
39 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the role of nucleoside 5'-triphosphates in metabolism?

  • They facilitate cellular communication.
  • They act as enzymes.
  • They are structural components of nucleic acids.
  • They serve as energy carriers. (correct)

    • Which nucleoside triphosphate is primarily involved in carbohydrate metabolism?

  • CTP
  • UTP (correct)
  • GTP
  • ATP

    • What type of bond forms between nucleotides in a nucleic acid chain?

  • Hydrogen bonds
  • Covalent bonds
  • 3',5'-Phosphodiester bridges (correct)
  • Ionic bonds

    • Which process is primarily linked with the action of ATP?

    <p>Energy metabolism</p> Signup and view all the answers

    What is a common function of cyclic nucleotides?

    <p>They are involved in signal transduction.</p> Signup and view all the answers

    Which of the following is NOT a direct function of nucleoside 5'-triphosphates?

    <p>Serving as structural components of cells</p> Signup and view all the answers

    What characterizes the structure of DNA as compared to RNA?

    <p>Deoxyribose sugar versus ribose sugar</p> Signup and view all the answers

    Which type of RNA is responsible for carrying the message for protein synthesis?

    <p>Messenger RNA</p> Signup and view all the answers

    Which of the following statements accurately describes nucleic acids?

    <p>Nucleosides consist of a base bonded to a sugar.</p> Signup and view all the answers

    What is the complementary DNA sequence for the segment ATCGGCTAAGC written in the 3′-to-5′ direction?

    <p>TAGCCGATTCG</p> Signup and view all the answers

    Erwin Chargaff's observations indicated which of the following relationships in DNA?

    <p>The A:T ratio is nearly 1:1 across various organisms.</p> Signup and view all the answers

    Which statement about the base pairs in DNA is true?

    <p>Base pairs have essentially the same shape when paired correctly.</p> Signup and view all the answers

    What is the effect of hydroxide ion (OH-) on the C'2 hydroxyl group during RNA hydrolysis?

    <p>It abstracts a proton, resulting in a charged oxygen.</p> Signup and view all the answers

    What is a major factor contributing to the stability of the DNA double helix?

    <p>Hydrophobic effects from stacked base pairs.</p> Signup and view all the answers

    What is a product of the hydrolysis of RNA following the creation of a cyclic nucleotide?

    <p>It results in the hydrolysis into 2’ and 3’-monophosphate derivatives.</p> Signup and view all the answers

    Which of the following statements regarding RNA and DNA sugars is correct?

    <p>RNA contains ribose, while DNA contains deoxyribose.</p> Signup and view all the answers

    Which statement correctly describes semiconservative replication of DNA?

    <p>Each new helix contains both parental strands.</p> Signup and view all the answers

    Which statement about the direction nucleic acids are written in is false?

    <p>Nucleic acids are written in the 3′-to-5′ direction.</p> Signup and view all the answers

    What role do van der Waals forces play in DNA structure?

    <p>They contribute to the stability through base stacking.</p> Signup and view all the answers

    What role does DNA polymerase play in DNA synthesis?

    <p>It catalyzes the formation of phosphodiester bridges.</p> Signup and view all the answers

    What direction does chain elongation proceed during DNA synthesis?

    <p>5'-to-3' direction.</p> Signup and view all the answers

    What activity do many DNA polymerases possess to ensure accuracy during synthesis?

    <p>Activity to detect mismatched nucleotides and remove them.</p> Signup and view all the answers

    How do some viruses replicate their RNA genomes?

    <p>With the help of RNA-directed RNA polymerases.</p> Signup and view all the answers

    What is the primary role of transfer RNA (tRNA) in gene expression?

    <p>To carry amino acids to the ribosome for peptide-bond formation</p> Signup and view all the answers

    Which statement accurately describes the function of ribosomal RNA (rRNA)?

    <p>It catalyzes the formation of peptide bonds</p> Signup and view all the answers

    Which of the following accurately identifies the result of the transcription process?

    <p>Synthesis of messenger RNA (mRNA) from DNA</p> Signup and view all the answers

    What is the main requirement for RNA polymerase to synthesize RNA?

    <p>Double-stranded or single-stranded DNA template</p> Signup and view all the answers

    What distinguishes retroviruses from other types of viruses?

    <p>They convert single-stranded RNA to DNA</p> Signup and view all the answers

    Which RNA type is most abundant in E.coli, according to the relative amounts provided?

    <p>Ribosomal RNA (rRNA)</p> Signup and view all the answers

    In what direction does RNA synthesis occur?

    <p>5′ to 3′ direction</p> Signup and view all the answers

    What does reverse transcriptase specifically do in retroviruses?

    <p>Converts RNA into DNA</p> Signup and view all the answers

    What drives the synthesis of RNA during elongation?

    <p>Pyrophosphate hydrolysis</p> Signup and view all the answers

    If the DNA template strand is 3'–TCAAGGCGA–5', what is the resulting mRNA sequence?

    <p>5'–AGUUCCGCU–3'</p> Signup and view all the answers

    What characterizes the promoter sites for transcription?

    <p>Where RNA polymerase binds to initiate transcription</p> Signup and view all the answers

    What is the role of the terminator sequence in transcription?

    <p>To signal the end of transcription</p> Signup and view all the answers

    Which of the following best describes the structure of the terminator sequence in prokaryotes?

    <p>A stem-loop structure followed by U residues</p> Signup and view all the answers

    Which sequence is a common promoter element in eukaryotes?

    <p>CAAT box</p> Signup and view all the answers

    How does RNA polymerase recognize where to start transcription?

    <p>Through interaction with promoter sites</p> Signup and view all the answers

    What is the significance of the base composition found in newly synthesized RNA?

    <p>It complements the DNA template strand</p> Signup and view all the answers

    Study Notes

    Nucleoside 5'-Triphosphates Are Carriers of Chemical Energy

    • Nucleoside 5'-triphosphates are critical for metabolism due to their high-energy phosphoric anhydride bonds
    • The bases in nucleotides serve as recognition units
    • Cyclic nucleotides act as signal molecules and regulators of cellular processes
    • ATP is essential for energy metabolism
    • GTP drives protein synthesis
    • CTP drives lipid synthesis
    • UTP drives carbohydrate metabolism

    The Structure of a Nucleic Acid Chain Can Be Simplified

    • Nucleic acid chains are represented by the sequence of their bases
    • The 5'-ends of the chains are at the top; the 3'-ends are at the bottom.

    What Are the Different Classes of Nucleic Acids?

    • DNA exists in one form and has one primary purpose
    • RNA exists in three (or four) types and has three (or four) purposes
      • Ribosomal RNA (rRNA) forms the structural and functional basis of ribosomes
      • Messenger RNA (mRNA) carries the genetic code for protein synthesis
      • Transfer RNA (tRNA) carries amino acids to the ribosomes for protein synthesis
      • Other types include small nuclear RNA and small non-coding RNAs

    The Structure of DNA

    • Each phosphodiester bridge in a nucleic acid backbone has a negative charge
    • Nucleosides consist of a base bonded to a sugar
    • DNA contains the bases adenine (A), thymine (T), guanine (G), and cytosine (C)
    • Nucleic acids are conventionally written in the 5'-to-3' direction

    Base Pairing in DNA

    • Guanine pairs with cytosine (G:C)
    • Adenine pairs with thymine (A:T)
    • The base pairs have similar shapes
    • Hydrogen bonds hold the base pairs together

    Chargaff's Rules

    • The A:T and G:C ratios are nearly 1:1 in different organisms
    • The A:G ratio varies between organisms

    Stability of the Double Helix

    • Base stacking contributes to the stability of the double helix due to hydrophobic interactions
    • Van der Waals forces also stabilize stacked base pairs

    DNA Replication

    • DNA replication involves the unwinding of the double helix and separation of the two strands
    • Each strand serves as a template for the synthesis of a new complementary strand
    • DNA polymerase catalyzes the addition of nucleotides to the growing strand in a 5'-to-3' direction
    • The process is semiconservative, meaning that each new helix contains one parental strand and one newly synthesized strand

    RNA

    • RNA is less susceptible to hydrolysis by dilute base than DNA due to its shorter glycosidic bond
    • Hydrolysis of RNA by dilute base involves:
      • An OH- abstracts a proton from the C'2 hydroxyl group
      • The charged oxygen attacks the positive phosphorus, breaking the phosphodiester bond
      • The cyclic nucleotide is hydrolyzed by water to form a mixture of 2'- and 3'-monophosphate derivatives

    Gene Expression

    • Gene expression is the process of converting genetic information from DNA into functional molecules
    • It involves two steps:
      • Transcription: DNA is transcribed into mRNA
      • Translation: mRNA is translated into proteins

    Types of RNA

    • Messenger RNA (mRNA): serves as a template for protein synthesis
    • Transfer RNA (tRNA): carries amino acids to the ribosome for protein synthesis
    • Ribosomal RNA (rRNA): forms the major component of ribosomes and acts as a catalyst for protein synthesis

    RNA Polymerase

    • RNA polymerase synthesizes RNA from a DNA template
    • It does not require a primer
    • The process involves the elongation of the RNA strand in a 5'-to-3' direction using ribonucleoside triphosphates (ATP, GTP, UTP, and CTP)
    • The reaction is driven by pyrophosphate hydrolysis

    Transcription

    • Transcription begins at promoter sites and ends at terminator sites
    • Promoter sites are regions on DNA that bind RNA polymerase and determine the start of transcription
    • Terminator sequences are regions that signal the end of transcription

    Promoter Sites

    • Prokaryotes: Pribnow box (-10 region), -35 region
    • Eukaryotes: TATA box (Hogness box), CAAT box

    Transcription Termination

    • Prokaryotes: terminator sequences or rho protein
    • Eukaryotes: less well-defined, may involve specific sequences or protein factors
    • Terminator sequences often involve a stem-loop structure followed by a sequence of U residues

    Complementarity Between DNA and RNA

    • The base sequence of mRNA is complementary to the template strand of DNA
    • Uracil (U) in RNA replaces thymine (T) in DNA

    Key Characteristics of DNA Synthesis

    • Requires four deoxynucleoside 5'-triphosphates and Mg2+
    • Occurs on a pre-existing DNA template
    • Requires a primer to initiate synthesis
    • Chain elongation proceeds in the 5'-to-3' direction
    • Many DNA polymerases have nuclease activity to remove mismatched nucleotides

    Viral RNA Genomes

    • Some viruses have RNA genomes that are replicated by RNA-directed RNA polymerases
    • Retroviruses have single-stranded RNA genomes that are converted to DNA by reverse transcriptase

    Hypochromism

    • Hypochromism is the decrease in UV absorbance at 260 nm when DNA is in a double-stranded form
    • This phenomenon is due to stacking interactions between base pairs
    • It is an indication of the double helix formation

    X-Ray Diffraction of DNA

    • X-ray diffraction studies provided essential information about DNA structure
    • They revealed that DNA is a double helix with a helical structure

    Importance of Chargaff's Discovery

    • Chargaff's discovery of the equivalence of A and T, and G and C, was essential for understanding DNA structure
    • It supported the idea of base pairing in DNA and provided evidence for the Watson-Crick model

    Semiconservative Replication

    • DNA replication is semiconservative, meaning each new DNA molecule contains one parental strand and one newly synthesized strand

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Lecture 7.pptx PDF

    Description

    Explore the vital role of nucleoside 5'-triphosphates in metabolism and their function as energy carriers. This quiz delves into the structure of nucleic acid chains, the significance of phosphodiester bridges, and the classes of nucleic acids including DNA and RNA. Test your knowledge on these essential biomolecules.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser