Determining Amino Acid Sequence Quiz
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Questions and Answers

What technique did Sanger use to analyze the amino acid sequence of proteins?

  • Electrophoresis
  • Fragmentation and overlap analysis (correct)
  • Mass spectrometry
  • Crystallography

    • How does the primary structure of a protein influence its higher-order structures?

  • By dictating the sequence of nucleotides in DNA
  • By specifying the order and identity of amino acids (correct)
  • By altering the temperature during synthesis
  • By determining the pH levels of the environment

    • What bonding pattern primarily stabilizes the secondary structure of proteins?

  • Hydrogen bonding between NH and CO groups (correct)
  • Covalent bonds between peptide backbones
  • Van der Waals forces
  • Ionic bonds between side chains

    • How many amino acids are present per turn in an α helix structure?

    <p>3.6</p> Signup and view all the answers

    What is a key characteristic of the β sheet structure in proteins?

    <p>It exhibits the maximum hydrogen bonding</p> Signup and view all the answers

    What defines parallel β sheets in protein structure?

    <p>The polypeptides forming the sheets have the same polarity</p> Signup and view all the answers

    What physical shape characterizes the α helix in protein structure?

    <p>Spiral and tubular</p> Signup and view all the answers

    In the context of protein structure, what do the 'peaks' and 'troughs' of a β sheet refer to?

    <p>The local folding of the polypeptide chain</p> Signup and view all the answers

    What primarily determines the final folded shape of a protein?

    <p>The primary structure</p> Signup and view all the answers

    Which of the following describes a protein domain?

    <p>A discrete, locally folded unit of tertiary structure with a specific function</p> Signup and view all the answers

    Globular proteins can comprise which of the following structural elements?

    <p>A combination of α helices and β sheets</p> Signup and view all the answers

    What is unique about quaternary structure in proteins?

    <p>It focuses on subunit interactions and assembly.</p> Signup and view all the answers

    Which of the following statements about globular proteins is FALSE?

    <p>Globular proteins consist solely of domains.</p> Signup and view all the answers

    What remains unpredictable in terms of protein structure?

    <p>The exact folding of larger proteins</p> Signup and view all the answers

    What is the primary function of polysaccharides?

    <p>Structure and storage</p> Signup and view all the answers

    How long is a typical domain composed of amino acids?

    <p>50–350 amino acids</p> Signup and view all the answers

    Which type of structure refers to the arrangement of protein subunits?

    <p>Quaternary structure</p> Signup and view all the answers

    Which of the following is considered a monosaccharide?

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

    What is the formula that sugars commonly follow?

    <p>C(n)H(2n)O(n)</p> Signup and view all the answers

    What classification do sugars with four carbon atoms belong to?

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

    In which form does D-glucose primarily exist within cells?

    <p>In dynamic equilibrium between linear and ring forms</p> Signup and view all the answers

    Which of the following is a characteristic of sugars categorized as ketoses?

    <p>They have an internal carbonyl group</p> Signup and view all the answers

    How many carbon atoms do pentoses contain?

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

    What type of sugar is D-glucose classified as?

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

    What is the directionality of a polynucleotide formed by nucleotides?

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

    Which nucleotides pair through hydrogen bonding in DNA?

    <p>A pairs with T, and G pairs with C</p> Signup and view all the answers

    What is a key feature of nucleic acid synthesis?

    <p>Correct base pairing with a template is essential</p> Signup and view all the answers

    What significant structure of DNA was proposed by Francis Crick and James Watson?

    <p>Double-stranded helix</p> Signup and view all the answers

    How are nucleotides linked in a polynucleotide chain?

    <p>By 3′, 5′ phosphodiester bonds</p> Signup and view all the answers

    How many hydrogen bonds form between A and T in DNA?

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

    What is the role of complementary base pairing in nucleic acids?

    <p>It ensures correct nucleotide order during synthesis</p> Signup and view all the answers

    What type of strands form the DNA double helix?

    <p>Antiparallel and complementary</p> Signup and view all the answers

    What is the main component of starch that accounts for 70-90% of its structure?

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

    What type of linkages does chitin primarily consist of?

    <p>β(1→4) bonds</p> Signup and view all the answers

    Why is cellulose considered a major structural polysaccharide in plants?

    <p>It forms rigid linear rods that aggregate into microfibrils.</p> Signup and view all the answers

    Which type of glycosidic bond is primarily found in starch and glycogen?

    <p>α glycosidic bonds</p> Signup and view all the answers

    Which of the following statements about cellulose is true?

    <p>Cellulose is abundant in plant cell walls.</p> Signup and view all the answers

    What distinguishes the cellulose found in fungal cell walls from that in plant cell walls?

    <p>The presence of β(1→3) linkages</p> Signup and view all the answers

    In which organelle is starch primarily stored in plants?

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

    Which two sugars primarily compose bacterial cell walls?

    <p>GlcNAc and MurNAc</p> Signup and view all the answers

    Study Notes

    Determining Amino Acid Sequence

    • Frederick Sanger received the Nobel Prize for sequencing the insulin protein, utilizing protein cleavage into smaller fragments.
    • His method involved analyzing overlapping fragments to determine amino acid order, influencing future protein sequencing techniques.

    Importance of Primary Structure

    • Primary structure is crucial both genetically and structurally, dictated by nucleotide order in messenger RNA.
    • The sequence of amino acids directs the formation of secondary and tertiary protein structures.

    Secondary Structure

    • Secondary structure is formed by hydrogen bonding between NH and CO groups in the polypeptide backbone.
    • Two primary patterns emerge: α helices and β sheets.

    The α Helix

    • The α helix features a spiral shape with R groups extending outward; it has 3.6 amino acids per turn.
    • Hydrogen bonds form between NH groups of one amino acid and CO groups of another one turn away.

    The β Sheet

    • The β sheet has a sheetlike conformation with alternated peaks and troughs due to the arrangement of polypeptide atoms.
    • Characterized by extensive hydrogen bonding, it can form with different polypeptides or regions of the same polypeptide and can be parallel or antiparallel in orientation.

    Structure of Hair

    • Hair structure exemplifies the arrangements of proteins in cellular components.

    Globular Proteins

    • Globular proteins are compact structures with unique tertiary forms, comprising most enzymes.
    • They can be primarily α helical, β sheet, or a combination, often containing multiple functional domains.

    Protein Domains

    • A domain is a folded region of a protein, typically 50–350 amino acids long, with specific functions.
    • Proteins often share common domains, and proteins with multiple functions usually contain separate domains for each role.

    Prediction of Tertiary Structure

    • Primary structure dictates a protein's final folded shape, but predicting folding patterns, especially for larger proteins, remains challenging.

    Quaternary Structure

    • Quaternary structure involves the interaction and assembly of multiple protein subunits, characteristic of multimeric proteins.
    • Proteins can consist of identical or different polypeptide subunits, exemplified by hemoglobin.

    Nucleic Acids

    • Nucleic acids are polymers of nucleotides linked via phosphodiester bonds, exhibiting 5′ to 3′ directionality.
    • Nucleotide sequences are conventionally expressed in this direction, with base pairing essential for synthesis.

    Complementary Base Pairing

    • A pairs with T through two hydrogen bonds, while G pairs with C through three hydrogen bonds, a fundamental property of nucleic acids.

    DNA Structure

    • The double helix structure of DNA, proposed by Watson and Crick in 1953, consists of two antiparallel strands that twist around each other.
    • This structure accounts for DNA's replication mechanism and complies with its chemical properties.

    RNA Structure

    • RNA typically exists as a single strand but can base pair within the same molecule, forming less extensive structures compared to DNA.

    Polysaccharides

    • Polysaccharides are long-chain polymers of sugars, serving structural and storage roles, consisting of repeating units called monosaccharides.
    • Short sugar polymers or oligosaccharides can attach to cell surface proteins.

    Classification of Sugars

    • Sugars vary from three to seven carbons, classified as trioses, tetroses, pentoses, hexoses, and heptoses.

    Glucose

    • D-glucose (C6H12O6) is the most common monosaccharide, existing in dynamic equilibrium between linear and cyclic forms.
    • It forms the structural basis of carbohydrates, with a formula of CnH2nOn.

    Starch

    • Starch, composed of amylose and amylopectin, is stored in plastids like chloroplasts and amyloplasts, crucial for energy storage in plants.
    • Amylopectin contains branches, while amylose is generally unbranched.

    Structural Polysaccharides

    • Cellulose is the primary structural polysaccharide in plants, composed of β-D-glucose repeating units, indigestible by most mammals.
    • Fungal and bacterial cell wall compositions differ, involving unique sugar linkages.

    Chitin

    • Chitin consists entirely of GlcNAc units linked by β(1→4) bonds, found in fungal cell walls and exoskeletons of insects and crustaceans.

    Glycosidic Bonds

    • The type of glycosidic bonds (α vs β) significantly affects polysaccharide structure.
    • α-linked polysaccharides like starch form loose helices, while β-linked cellulose forms rigid rods, contributing to structural integrity in plant and fungal cells.

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    Description

    This quiz explores the groundbreaking work of Fred Sanger in determining the amino acid sequence of proteins, including the insulin protein. Learn about the methods he developed and their impact on protein sequencing. Test your knowledge on protein structure and sequencing techniques used in biochemistry.

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