Drawing Peptides Quiz
40 Questions
0 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 ionized form of the carboxylic acid group in amino acids at physiological pH?

  • −COOH
  • −COO+
  • −COO2−
  • −COO− (correct)

    • Which statement best describes zwitterions?

  • They are amino acids that do not ionize.
  • They are amino acids with only a positive charge.
  • They have both positive and negative charges, resulting in an overall zero charge. (correct)
  • They are exclusively present in acidic solutions.

    • Why are all α-amino acids except glycine chiral?

  • They are attached to four different atoms. (correct)
  • They lack an α-carbon.
  • They have identical atoms attached to the α-carbon.
  • They have a symmetrical structure.

    • In a Fischer projection of an amino acid, where is the carboxylate group placed?

    <p>At the top</p> Signup and view all the answers

    For which type of isomer are the only amino acids used in protein incorporation?

    <p>L isomers</p> Signup and view all the answers

    Which amino acid group is responsible for the positive charge in ionized amino acids?

    <p>−NH3 group</p> Signup and view all the answers

    What characteristic defines the L isomer of amino acids compared to the D isomer?

    <p>The −NH3 group is on the left side.</p> Signup and view all the answers

    How do amino acids typically behave in most body fluids regarding ionization?

    <p>They exist solely as zwitterions.</p> Signup and view all the answers

    What amino acid is at the N-terminal of the tripeptide Gly-Ser-Met?

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

    Which bond is primarily formed between amino acids to create a peptide?

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

    What is the C-terminal amino acid in the tripeptide Gly-Ser-Met?

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

    What is the three-letter abbreviation for Serine?

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

    Which of the following sequences correctly represents the order of amino acids in the tripeptide Gly-Ser-Met?

    <p>Gly-Ser-Met</p> Signup and view all the answers

    When drawing the peptide bond formation between Valine and Threonine, which group is removed from Valine?

    <p>Carboxyl group</p> Signup and view all the answers

    If the dipeptide Val-Pro is constructed, what would be a characteristic feature of the peptide bond formation?

    <p>A water molecule is released</p> Signup and view all the answers

    What characterizes nonpolar amino acids?

    <p>They have hydrogen, alkyl, or aromatic R groups.</p> Signup and view all the answers

    What is the condensed structural formula of the tripeptide formed from Glycine, Alanine, and Valine?

    <p>Gly-Ala-Val</p> Signup and view all the answers

    Which group of amino acids contains R groups that interact with water?

    <p>Polar Neutral Amino Acids</p> Signup and view all the answers

    What is the significance of the isoelectric point (pI) in relation to amino acids?

    <p>It is the pH at which an amino acid has a net neutral charge.</p> Signup and view all the answers

    How do polar basic amino acids behave at pH levels higher than their pI?

    <p>They exist as negative ions.</p> Signup and view all the answers

    Which functional group is featured in polar acidic amino acids?

    <p>Carboxylate (-COO-) group</p> Signup and view all the answers

    When does an amino acid exist as a positive ion?

    <p>When the pH is lower than its pI</p> Signup and view all the answers

    What kind of R groups do polar neutral amino acids contain?

    <p>Hydroxyl, thiol, or amide groups</p> Signup and view all the answers

    What happens to amino acids when the surrounding solution becomes more basic than their pI?

    <p>They exist as negative ions.</p> Signup and view all the answers

    What is the main structural feature of a beta-pleated sheet?

    <p>Hydrogen bonds between carbonyl groups and N-H groups in adjacent chains</p> Signup and view all the answers

    What structural form do beta-amyloid proteins take in a healthy brain?

    <p>Alpha helices</p> Signup and view all the answers

    What is the composition of collagen fibers?

    <p>Three alpha helical polypeptides woven together</p> Signup and view all the answers

    Which of the following describes a protein's tertiary structure?

    <p>Overall 3D shape determined by R group interactions</p> Signup and view all the answers

    In Alzheimer’s disease, what happens to beta-amyloid proteins?

    <p>They shift from alpha helices to beta-pleated sheets</p> Signup and view all the answers

    Which characteristic of collagen contributes to its structural integrity?

    <p>Three intertwined alpha helices</p> Signup and view all the answers

    What often distinguishes the brain tissue of Alzheimer's patients?

    <p>Presence of plaques made of beta-pleated sheets</p> Signup and view all the answers

    What triggers the twisting and bending of a polypeptide chain during tertiary structure formation?

    <p>Attractions and repulsions between R groups</p> Signup and view all the answers

    What is the primary role of myoglobin in skeletal muscle?

    <p>To store oxygen</p> Signup and view all the answers

    Which type of protein is characterized by a long, thin, fiber-like shape?

    <p>Fibrous proteins</p> Signup and view all the answers

    What characterizes the quaternary structure of a protein?

    <p>Multiple polypeptide chains interacting</p> Signup and view all the answers

    Which two types of keratins are mentioned as fibrous proteins?

    <p>Alpha and beta keratins</p> Signup and view all the answers

    How many amino acids are there in the myoglobin protein structure?

    <p>153</p> Signup and view all the answers

    What type of bonds primarily stabilizes the secondary structure of proteins?

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

    Which of the following is a key feature of hemoglobin?

    <p>It consists of four polypeptide subunits</p> Signup and view all the answers

    Which interaction is crucial for the tertiary structure of proteins?

    <p>Interactions between R groups</p> Signup and view all the answers

    Study Notes

    Drawing Peptides

    • Tripeptides consist of three amino acids linked by peptide bonds.
    • For Gly-Ser-Met:
      • Remove an oxygen atom from the carboxylate group of Gly (N-terminal).
      • Remove two hydrogen atoms from the ammonium group of Ser (adjacent amino acid).
    • Connection of amino acids through peptide bonds is essential in forming peptides.

    Ionization of Amino Acids

    • Amino acids typically exist as zwitterions at physiological pH.
    • The amino group (-NH₂) becomes ionized (-NH₃⁺) while the carboxylic acid (-COOH) loses a proton to form (-COO⁻).
    • Zwitterions maintain overall neutrality despite having both positive and negative charges.

    Amino Acid Stereoisomers

    • All α-amino acids except glycine are chiral, with the α-carbon attached to four different atoms.
    • Two isomer forms exist: D and L forms, with L being the only form used in proteins.
    • Fischer projections can be used to depict the arrangement of amino acids.

    Classification of Amino Acids

    • Nonpolar amino acids have hydrophobic R groups (e.g., hydrogen, alkyl, or aromatic).
    • Polar amino acids are hydrophilic and can be categorized:
      • Polar Neutral: Contains -OH, -SH, or -CONH₂ groups.
      • Polar Acidic: Contains carboxylate groups.
      • Polar Basic: Contains amino groups that can ionize.

    Levels of Protein Structure

    • Primary Structure: Sequence of amino acids linked by peptide bonds.
    • Secondary Structure: Involves hydrogen bonding to form α-helices and β-pleated sheets.
    • Tertiary Structure: Three-dimensional shape due to R group interactions, involving folding and twisting.
    • Quaternary Structure: Combination of multiple polypeptide chains to form a functional protein (e.g., hemoglobin with two α and two β chains).

    Specific Protein Structures

    • β-Pleated Sheet: Formed by hydrogen bonds between carbonyl groups and N-H groups of adjacent polypeptide chains.
    • Triple Helix: Structure of collagen made from three intertwined polypeptide chains, providing structural strength.
    • Globular Proteins: Compact, spherical structures like myoglobin, which store oxygen.
    • Fibrous Proteins: Long, fiber-like shapes, involved in structural roles in tissues (e.g., keratins in hair and feathers).

    Alzheimer’s Disease

    • Characterized by memory loss and difficulties in daily tasks.
    • Beta-amyloid proteins normally exist in an α-helical form but misfold into β-pleated sheets in affected individuals, forming insoluble plaques.

    Ionized Forms and Isoelectric Point

    • Zwitterions form at the isoelectric point (pI); amino acids can exist as positive ions in acidic solutions and as negative ions in basic solutions relative to their pI.

    Hemoglobin Functionality

    • Hemoglobin's quaternary structure is crucial for transporting oxygen, requiring the proper assembly of its four polypeptide subunits.

    Exercise and Application

    • Identify structures present in proteins:
      • Peptide bonds are found in primary and higher structures.
      • Hydrogen bonds are present in secondary (between chains) and tertiary (within chains) structures.

    Studying That Suits You

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

    Quiz Team

    Related Documents

    Proteins and Amino Acids Notes PDF

    Description

    Test your knowledge on the structure and naming of peptides with this quiz focused on the tripeptide Gly-Ser-Met. You'll draw the structure and apply specific rules for constructing peptide sequences. Perfect for students in natural sciences!

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser