Biochem 1.1 . Amino Acids and Stereochemistry
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Biochem 1.1 . Amino Acids and Stereochemistry

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Questions and Answers

What is the one-letter code for phenylalanine?

  • F (correct)
  • Y
  • A
  • P

    • Which amino acid is represented by the three-letter code ‘Arg’?

  • Proline
  • Arginine (correct)
  • Tyrosine
  • Phenylalanine

    • What distinguishes tyrosine from phenylalanine?

  • Presence of a carboxyl group
  • Presence of a sulfur group
  • Presence of an amine group
  • Presence of a hydroxyl group (correct)

    • Which amino acid has a phenyl group?

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

    What is the primary structure of arginine at physiological pH?

    <p>A combination of H3N+, COO-, and NH</p> Signup and view all the answers

    Which of the following amino acids is a phenyl-substituted alanine?

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

    Why is 'F' chosen as the one-letter code for phenylalanine?

    <p>Because it sounds like 'Fenylalanine'</p> Signup and view all the answers

    What component is missing from phenylalanine that is present in tyrosine?

    <p>A hydroxyl group</p> Signup and view all the answers

    Which of the following amino acids has the abbreviation 'Glu'?

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

    What is the one-letter code for Lysine?

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

    Which amino acid has a side chain containing -NH2 group?

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

    Which of the following is NOT an amino acid mentioned?

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

    What structural component is common to all amino acids?

    <p>A carboxyl group (-COOH)</p> Signup and view all the answers

    What does a clockwise rotation of plane-polarized light by an amino acid indicate about its stereochemistry?

    <p>The amino acid is in its R-form.</p> Signup and view all the answers

    Which amino acid is noted for having an R-configuration at its chiral center due to the priority of the sulfur atom?

    <p>L-cysteine</p> Signup and view all the answers

    Which chiral center configuration does L-threonine possess?

    <p>R-configuration</p> Signup and view all the answers

    What is true regarding the configurations of L-amino acids and their relationship to the R/S system?

    <p>All L-amino acids have S-configurations at the alpha carbon except for cysteine.</p> Signup and view all the answers

    In pathological conditions, which amino acids can accumulate as their respective stereoisomers?

    <p>Allothreonine and Alloisoleucine</p> Signup and view all the answers

    What is the primary role of amino acids in biological systems?

    <p>Building blocks of proteins</p> Signup and view all the answers

    How many proteinogenic amino acids are there?

    <p>20</p> Signup and view all the answers

    What determines the properties of an amino acid?

    <p>The amino acid's unique structure</p> Signup and view all the answers

    Which part of the amino acid structure is critical for its interaction with other molecules?

    <p>The R group (side chain)</p> Signup and view all the answers

    What is a common feature of all amino acids?

    <p>They all contain an amino group and a carboxyl group</p> Signup and view all the answers

    In the provided structure of amino acids, what is the significance of the 'R' group?

    <p>It determines the amino acid's identity and characteristics</p> Signup and view all the answers

    Which amino acid is represented by the abbreviation 'Thr'?

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

    Which amino acid is a precursor to serine?

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

    What characteristic distinguishes r-glyceraldehyde from o-glyceraldehyde?

    <p>Rotation of plane-polarized light</p> Signup and view all the answers

    What configuration do amino acids that are similar to r-glyceraldehyde possess?

    <p>L-configured</p> Signup and view all the answers

    Which of the following is true about L-amino acids?

    <p>They are almost exclusively used in proteins.</p> Signup and view all the answers

    Which statement about the designation of amino acids as L- or D- is accurate?

    <p>It indicates their molecular structure similarity to glyceraldehyde.</p> Signup and view all the answers

    What is a known exception regarding L-amino acids in certain bacteria?

    <p>They are always converted to D-amino acids.</p> Signup and view all the answers

    Which of the following statements is false regarding amino acids?

    <p>o-glyceraldehyde is structurally related to D-amino acids.</p> Signup and view all the answers

    What specific property defines the distinction between levorotatory and dextrorotatory compounds?

    <p>The angle of light rotation</p> Signup and view all the answers

    Which structural feature is shared between r-glyceraldehyde and L-amino acids?

    <p>The configuration of the chiral center</p> Signup and view all the answers

    Study Notes

    Arginine

    • Arginine is a proteinogenic amino acid with the one-letter code "R"
    • Arginine's structure contains a guanidinium group, which is a positively charged functional group.

    Phenylalanine

    • Phenylalanine is a proteinogenic amino acid with the one-letter code "F"
    • It has a benzene ring attached to its side chain.
    • Phenylalanine is an aromatic amino acid.

    Tyrosine

    • Tyrosine is identical to phenylalanine, except for a hydroxyl group on its benzene ring.
    • Tyrosine is also an aromatic amino acid.

    Glyceraldehyde and Amino Acid Stereochemistry

    • D-glyceraldehyde is dextrorotatory, rotating plane-polarized light clockwise.
    • L-glyceraldehyde is levorotatory, rotating plane-polarized light counterclockwise.
    • The chiral center in L-amino acids has a similar configuration to L-glyceraldehyde.
    • The chiral center in D-amino acids has a similar configuration to D-glyceraldehyde.
    • Note: While the L- and D- designations refer to structural similarity to glyceraldehyde, they do not indicate how the amino acid rotates plane-polarized light.
    • L-amino acids are the predominant form found in proteins.

    Chirality in Side Chains

    • Cysteine, threonine, and isoleucine all have chiral centers in their side chains.
    • Cysteine's chiral center has an R-configuration, unlike other L-amino acids which have an S-configuration.
    • Threonine's chiral center has an R-configuration.
    • Isoleucine's chiral center has an S-configuration.
    • Allothreonine and alloisoleucine, the enantiomers of threonine and isoleucine, are not common in healthy organisms.

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    Description

    This quiz covers key concepts related to amino acids, including arginine, phenylalanine, and tyrosine. It also addresses the stereochemistry of glyceraldehyde and its relation to amino acids. Test your understanding of their structures and properties!

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