Lecture 19 – Protein Structure: Amnio acids and sequence
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Questions and Answers

How many commonly found amino acids are there in proteins?

  • 18
  • 20 (correct)
  • 22
  • 24

    • Which type of amino acids are considered hydrophilic?

  • Nonpolar amino acids
  • Charged and polar amino acids (correct)
  • Aromatic amino acids
  • Aliphatic amino acids

    • What characterizes positively charged (basic) amino acids?

  • Fully protonated at low pH (correct)
  • Fully deprotonated at high pH
  • Have no ionizable groups
  • Are always hydrophobic

    • What does a low pKa value indicate about an acid?

    <p>It is a strong acid.</p> Signup and view all the answers

    Which amino acid is known for its role in forming disulfide bonds?

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

    What is the primary function of disulfide bonds in proteins?

    <p>To stabilize protein structure</p> Signup and view all the answers

    What is the general structure of an amino acid?

    <p>Amino group, carboxyl group, R group, hydrogen atom</p> Signup and view all the answers

    Which statement best describes hydrophobic amino acids?

    <p>They are typically located in the interior of globular proteins.</p> Signup and view all the answers

    What is the term for a chain of two amino acids?

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

    How does the pH affect the ionization of amino acids?

    <p>It determines the charge state of the amino acids.</p> Signup and view all the answers

    Which amino acid is known for providing flexibility in proteins?

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

    What is the significance of the pKa value in amino acids?

    <p>It predicts the protonation state at a given pH.</p> Signup and view all the answers

    What type of bond forms between two cysteine residues?

    <p>Disulfide bond</p> Signup and view all the answers

    Which amino acid has a side chain that can engage in hydrogen bonding due to its hydroxyl group?

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

    What is the backbone structure of a polypeptide?

    <p>N-Cα-C-N-Cα-C</p> Signup and view all the answers

    What do we call the end of a polypeptide with a free amino group?

    <p>N-terminal</p> Signup and view all the answers

    What happens to the thiol (-SH) group of cysteine in a hydrophobic environment?

    <p>It remains uncharged and stable.</p> Signup and view all the answers

    Which of the following amino acids is classified as aromatic?

    Signup and view all the answers

    What is the significance of the Henderson-Hasselbalch equation in relation to amino acids?

    <p>It predicts the pH of buffer solutions.</p> Signup and view all the answers

    What is the common name for a peptide composed of more than 50 amino acids?

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

    Which amino acid is known for its role in stabilizing alpha-helices in proteins?

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

    What type of amino acids are typically found at the water/protein interface?

    <p>Hydrophilic amino acids</p> Signup and view all the answers

    What is the role of polar amino acids in proteins?

    <p>Engaging in hydrogen bonding</p> Signup and view all the answers

    Which amino acid's side chain is considered reactive due to its thiol group?

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

    What is the first protein to be sequenced?

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

    How are amino acids represented in protein sequences?

    <p>By their 1-letter or 3-letter codes</p> Signup and view all the answers

    What is the primary characteristic of aromatic amino acids?

    <p>They have a ring structure.</p> Signup and view all the answers

    What happens to the charge of acidic amino acids at low pH?

    <p>They become positively charged.</p> Signup and view all the answers

    What stabilizes the structure of proteins in an oxidizing environment?

    <p>Disulphide bonds</p> Signup and view all the answers

    Which of the following statements is true about the sequencing of proteins?

    <p>Proteins are often sequenced indirectly via DNA.</p> Signup and view all the answers

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