Amino Acids and Peptide Bonds Quiz
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Questions and Answers

What is the maximum number of different dipeptides that can be formed from 21 different amino acids?

  • 21
  • 441 (correct)
  • 462
  • 2100

    • Which of the following statements is true regarding polypeptides?

  • Polypeptides are linear and cannot form branched structures.
  • Polypeptides have fewer than 8 amino acid residues.
  • Polypeptides consist of one or more peptide chains. (correct)
  • Polypeptides cannot contain peptide bonds.

    • What is the significance of the resonance in peptide bonds?

  • It increases the flexibility of the peptide chain.
  • It causes rigidity in the peptide structure. (correct)
  • It permits the formation of cyclic peptides.
  • It allows free rotation around the bond.

    • Which reaction type is involved in peptide bond formation?

    <p>Dehydration synthesis reaction</p> Signup and view all the answers

    How many different polypeptides can be theoretically formed using 100 amino acids?

    <p>1.27 x 10^130</p> Signup and view all the answers

    What determines the rigidity of peptides?

    <p>The delocalization of electrons in peptide bonds</p> Signup and view all the answers

    Which of the following is NOT considered a type of peptide?

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

    What is the estimated total number of atoms in the universe in comparison to the number of possible 100 amino acid proteins?

    <p>Greater than possible proteins</p> Signup and view all the answers

    What type of molecular link do disulfide bonds create in polypeptides?

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

    Which molecule can be formed through the reduction of disulfides?

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

    Which amino acids are part of the tetrapeptide named alanylserylglycylaspartic acid?

    <p>Ala, Ser, Gly, Asp</p> Signup and view all the answers

    What is the structural feature of conotoxin G I?

    <p>Blocks nicotinic cholinoreceptors</p> Signup and view all the answers

    How many amino acid residues are present in the conotoxin G I sequence?

    <p>12</p> Signup and view all the answers

    What is the role of disulfide bonds in the structure of peptides?

    <p>They stabilize the three-dimensional structure</p> Signup and view all the answers

    Which of the following groups of amino acids makes up a heptapeptide as per the provided instructions?

    <p>Thr, Glu, Asn, Phe, Lys, Cys, Ile</p> Signup and view all the answers

    What type of peptide bond is to be emphasized when drawing the structure of the heptapeptide?

    <p>Red line</p> Signup and view all the answers

    What defines the peptide bond between amino acids?

    <p>A covalent bond with C–N double-bond character.</p> Signup and view all the answers

    Which of the following statements about peptide structure is correct?

    <p>The amide groups in peptides are planar.</p> Signup and view all the answers

    What distinguishes a dipeptide from other peptides?

    <p>It is the smallest possible peptide.</p> Signup and view all the answers

    Which of the following correctly describes a tripeptide?

    <p>A polymer containing three amino acids linked by two peptide bonds.</p> Signup and view all the answers

    What is the molecular weight requirement for a molecule to be classified as a protein?

    <p>5000 g/mol or greater.</p> Signup and view all the answers

    What type of linkage is described as occurring between two cysteine units?

    <p>Disulfide linkage.</p> Signup and view all the answers

    Which of the following peptides represents a tetrapeptide?

    <p>Gly-ser-phe-gly.</p> Signup and view all the answers

    What is the main structural characteristic of polypeptides?

    <p>Consist of a chain of many amino acids joined by peptide bonds.</p> Signup and view all the answers

    Which statement is true regarding peptide chains?

    <p>Peptide structures are written from N-terminal to C-terminal.</p> Signup and view all the answers

    Which amino acid primarily contributes to the formation of disulfide linkages?

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

    Study Notes

    Amino Acids and Peptide Bonds

    • Amino Acids can form peptide bonds to create peptides.
    • Proteins are molecules made up of one or more polypeptide chains.
    • Peptides are chains of amino acids linked by peptide bonds.
    • Peptides can be different lengths:
      • Dipeptides contain 2 amino acids.
      • Tripeptides contain 3 amino acids.
      • Oligopeptides contain a few amino acids.
      • Polypeptides contain many amino acids (up to 4000).

    Peptide Bond Formation

    • There are 20 naturally occurring amino acids encoded by the genome.
    • Each amino acid can combine with any other amino acid.
    • For a 100-amino acid protein, there are 1.27 x 10^130 possible combinations.
    • Peptide bonds are formed between the carboxyl group of one amino acid and the amino group of another.
    • The peptide bond is an amide bond which:
      • Has a partial double-bond character due to resonance.
      • Makes the peptide bond rigid and prevents rotation.
    • Peptide bond formation is a dehydration synthesis reaction, also known as a condensation reaction.

    Properties of Peptides

    • Peptides have an N-terminal and a C-terminal.
    • The N-terminal is the amino acid with the free amino group.
    • The C-terminal is the amino acid with the free carboxyl group.
    • Peptides can be classified by the number of amino acids they contain:
      • Dipeptide: 2 amino acids
      • Tripeptide: 3 amino acids
      • Polypeptide: many amino acids
      • Protein: 50 or more amino acids
    • Peptides are written with the N-terminal on the left and the C-terminal on the right.

    Disulfide Bonds in Peptides

    • Disulfide bonds are the only other covalent bond between amino acids in proteins and peptides.
    • They are formed between two cysteine residues.
    • Disulfide bonds can:
      • Connect polypeptide chains
      • Form a macrocycle within a single polypeptide chain

    Conotoxin G I

    • Conotoxin G I is a neurotoxin found in the venom of the cone snail Conus geographicus.
    • It is a 12-amino acid residue peptide with two disulfide bonds.
    • It blocks nicotinic acetylcholine receptors, leading to paralysis.

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    Related Documents

    Peptide Bond Formation PDF

    Description

    Test your knowledge on amino acids and peptide bonds. This quiz covers the basics of protein structure, peptide formation, and the various types of peptides. Understand the significance of peptide bonds in biochemistry and their role in building proteins.

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