Amino Acids and Functional Groups Quiz
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Questions and Answers

What functional groups are present in all a-amino acids?

  • Carboxyl group and phosphate group
  • Amino group and hydroxyl group
  • Carboxyl group and hydroxyl group
  • Amino group and carboxyl group (correct)

    • Which statement accurately describes proline among amino acids?

  • It is classified as a primary amino acid.
  • It is a secondary amino acid with a unique structure. (correct)
  • It has a simple hydrogen atom as its side chain.
  • It contains a carboxyl group but lacks an amino group.

    • What distinguishes different a-amino acids from each other?

  • The number of carbon atoms in their backbone
  • The presence of a carboxyl group
  • The structure of their R group (correct)
  • The type of amino group they contain

    • In what way does proline differ from other a-amino acids?

    <p>It includes a secondary amino group. (C)</p> Signup and view all the answers

    Which amino acid has a hydrogen atom as its side chain?

    <p>Glycine (D)</p> Signup and view all the answers

    What configuration is designated when the hydroxyl group is on the left in a Fischer projection?

    <p>L configuration (D)</p> Signup and view all the answers

    In a Fischer projection, if the hydroxyl group is on the right, what is the designation of that molecule?

    <p>D (C)</p> Signup and view all the answers

    Which amino acid configuration corresponds to L-glyceraldehyde?

    <p>L (B)</p> Signup and view all the answers

    For D-amino acids, where is the a-amino group located in a Fischer projection?

    <p>Right side (D)</p> Signup and view all the answers

    What is the reference carbon for determining the D and L configurations in amino acids?

    <p>Alpha carbon (C)</p> Signup and view all the answers

    How many absolute configurations can amino acids have?

    <p>Two (A)</p> Signup and view all the answers

    Which of the following amino acids is ribosomally incorporated into proteins in the L-configuration?

    <p>Alanine (C)</p> Signup and view all the answers

    What does the designation D refer to in molecular terms?

    <p>The absolute configuration with the hydroxyl group on the right (B)</p> Signup and view all the answers

    Which type of amino acids are commonly found in ribosomally synthesized proteins?

    <p>L-amino acids (D)</p> Signup and view all the answers

    What is the basis for the preference of L-amino acids over D-amino acids in proteins?

    <p>The reason is not known (A)</p> Signup and view all the answers

    Which system is most useful for describing the configuration of chiral compounds?

    <p>RS System (B)</p> Signup and view all the answers

    In the RS System, how is priority among substituents on a chiral carbon determined?

    <p>By the atomic number of bonded atoms (B)</p> Signup and view all the answers

    What type of antibiotics contain D-amino acids?

    <p>Tetrapeptide antibiotics (A)</p> Signup and view all the answers

    Which amino acid is used to illustrate the prioritization of groups around a chiral carbon?

    <p>Alanine (A)</p> Signup and view all the answers

    Which statement is true regarding D-amino acids?

    <p>They are found in some peptide antibiotics (A)</p> Signup and view all the answers

    Which factor does NOT influence the priority ranking in the RS system?

    <p>Presence of double bonds (D)</p> Signup and view all the answers

    What is true about enantiomers?

    <p>They are the same compound, differing only in the direction they rotate polarized light. (A)</p> Signup and view all the answers

    Which statement correctly describes diastereomers?

    <p>They are different compounds with distinct names and properties. (A)</p> Signup and view all the answers

    What distinguishes enantiomers from conformations?

    <p>Enantiomers involve non-superimposable mirror images. (B)</p> Signup and view all the answers

    What is an achiral amino acid?

    <p>It exists only in one configuration. (B)</p> Signup and view all the answers

    How does the DL system relate to amino acids?

    <p>It links the configuration of amino acids to that of a sugar molecule. (D)</p> Signup and view all the answers

    Which of the following statements is incorrect?

    <p>Achiral molecules have unique chirality. (D)</p> Signup and view all the answers

    What happens when the configuration of a molecule is altered?

    <p>Covalent bonds are rearranged and broken. (D)</p> Signup and view all the answers

    Which of these compounds is achiral?

    <p>Glycine (B)</p> Signup and view all the answers

    What units are used for the concentration of a sample in optical activity measurements?

    <p>Grams per milliliter (B)</p> Signup and view all the answers

    For a compound's specific rotation denoted as [α], what is the path length standardized to?

    <p>1 decimeter (C)</p> Signup and view all the answers

    Which notation indicates the use of a sodium lamp with a wavelength of 589 nm in optical activity measurements?

    <p>D line (B)</p> Signup and view all the answers

    What is the specific rotation value when the observed optical rotation is 0.671° with a concentration of 0.025 g/mL and path length of 0.5 dm?

    <p>53.68° (D)</p> Signup and view all the answers

    What defines standard (or proteinogenic) amino acids?

    <p>They are incorporated into proteins ribosomically. (C)</p> Signup and view all the answers

    How many different amino acids participate in protein synthesis?

    <p>22 (D)</p> Signup and view all the answers

    What type of acids are all standard amino acids classified as?

    <p>L-α-amino acids (B)</p> Signup and view all the answers

    Which of the following best describes the term 'specific rotation'?

    <p>It is a standard measure of optical activity. (B)</p> Signup and view all the answers

    Which amino acids contain hydroxyl groups in their side chains?

    <p>Serine, Threonine, Tyrosine (A)</p> Signup and view all the answers

    What type of group does arginine contain in its side chain?

    <p>Aguanidinium group (A)</p> Signup and view all the answers

    At neutral pH, which amino acids contain negatively charged groups?

    <p>Aspartate and Glutamate (B)</p> Signup and view all the answers

    Which amino acid has a side chain that contains a thiol group?

    <p>Cysteine (C)</p> Signup and view all the answers

    What distinguishes histidine's side chain from the others mentioned?

    <p>It can be positively charged near neutral pH. (D)</p> Signup and view all the answers

    Lysine and arginine are categorized under which type of amino acid based on their side chains?

    <p>Amino (C)</p> Signup and view all the answers

    What type of amino acids does serine belong to based on the nature of its side chain?

    <p>Hydroxyl (C)</p> Signup and view all the answers

    Which of the following amino acids does not have a charged polar side chain?

    <p>Cysteine (D)</p> Signup and view all the answers

    Flashcards

    Amino Acids

    Organic compounds that serve as building blocks for proteins, containing carbon, hydrogen, oxygen, and nitrogen.

    R-group (Side Chain)

    The group of atoms attached to the alpha carbon in an amino acid, determining its unique properties.

    Alpha Carbon (α-carbon)

    The carbon atom in an amino acid to which both the amino and carboxyl groups are attached.

    α-Amino Acid

    The functional group containing both the amino and carboxyl groups, found in all standard amino acids.

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    Proline

    An amino acid with a secondary amino group, making it unique compared to other amino acids.

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    Enantiomers

    Non-superimposable mirror images of a chiral molecule.

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    Diastereomers

    Stereoisomers that are not mirror images of each other. They have different properties.

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    Absolute configuration

    The specific spatial arrangement of atoms in a molecule. It determines its properties.

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    DL System

    A system to assign absolute configuration of a chiral molecule based on the stereochemistry of the 3-carbon aldose sugar glyceraldehyde.

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    Chiral molecule

    A type of stereoisomer that has a non-superimposable mirror image.

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    Achiral molecule

    A molecule that lacks a chiral center and does not have a non-superimposable mirror image.

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    Chiral center

    A carbon atom bonded to four different substituents.

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    Conformation

    The specific spatial arrangement of atoms in a molecule. It can be changed by rotation around bonds.

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    Absolute Configuration (D & L)

    The absolute configuration of a molecule's four substituents bonded to a chiral carbon, determined by the position of the hydroxyl group in a Fischer projection. 'L' configuration has the hydroxyl group on the left, while 'D' configuration has it on the right.

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    Glyceraldehyde

    A simple sugar molecule with three carbon atoms, used as a reference for determining the absolute configuration (D or L) of other chiral molecules.

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    Fischer Projection

    A projection formula representing a molecule in 2D, with the carbon chain drawn vertically and the substituents projected either horizontally or vertically. Useful for visualizing the relative positions of atoms/groups.

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    Chiral Carbon

    A carbon atom bonded to four different substituents, making it asymmetric and leading to the existence of stereoisomers.

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    R-group

    The chemical group responsible for the unique properties of an amino acid, attached to the alpha carbon.

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    Alpha Carbon

    The central carbon atom in an amino acid to which the amino group, carboxyl group, and R-group are attached.

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    Specific Rotation [α]

    Dividing observed rotation by path length and concentration; a unique property of a compound that describes its ability to rotate plane-polarized light.

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    Chiral Compound

    A molecule that contains a chiral center and can rotate polarized light. It has a non-superimposable mirror image.

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    Specific Rotation [α]

    The standard value for a compound's ability to rotate plane-polarized light under specific conditions (concentration of 1 g/mL, path length of 1 decimeter).

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    Achiral Compound

    A molecule that doesn't have a chiral center. It cannot rotate polarized light.

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    Standard (Proteinogenic) Amino Acids

    The set of 20 amino acids found in proteins, plus selenocysteine and pyrrolysine that are incorporated ribosomically into proteins.

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    Non-Standard Amino Acids

    Amino acids that are not found in proteins. They may have other functions in the body.

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    Hydroxyl-containing Amino Acids

    Amino acids with side chains containing hydroxyl groups (-OH), such as serine, threonine, and tyrosine.

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    Sulfur-containing Amino Acids

    Amino acids with side chains containing a sulfhydryl group (-SH), like cysteine.

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    Positively Charged Amino Acids

    Amino acids with side chains that are positively charged at neutral pH, such as lysine, arginine, and histidine.

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    Negatively Charged Amino Acids

    Amino acids with side chains that are negatively charged at neutral pH, such as aspartate and glutamate.

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    Aliphatic Amino Acids

    Amino acids with aliphatic side chains, which are non-polar and hydrophobic, such as glycine, alanine, valine, and leucine.

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    Aromatic Amino Acids

    Amino acids with aromatic side chains containing a ring structure, such as phenylalanine, tyrosine, and tryptophan.

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    Carboxylic-containing Amino Acids

    Amino acids with side chains containing carboxyl groups (-COOH), such as aspartate and glutamate.

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    Amide-containing Amino Acids

    Amino acids with side chains containing amide groups (-CONH2), such as asparagine and glutamine.

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    Study Notes

    Amino Acids and Proteins

    • Amino acids are organic compounds that contain carbon, hydrogen, oxygen, and nitrogen.
    • They are monomers that form proteins.
    • A-amino acids have an amino group (-NH2) and a carboxyl group (-COOH) attached to the same alpha carbon (α-carbon).
    • The side chain (R group) varies between different amino acids, making them unique.
    • Proline is a secondary amino acid, with a secondary amino group (-NH-).
    • Many naturally occurring amino acids aren't found in proteins; these structures differ from α-amino acids.

    Amino Acid Structure

    • The R group attached to the α-carbon distinguishes each amino acid.
    • Glycine has a hydrogen atom as its R group.
    • Lysine has a longer side chain.
    • Proline's secondary amino group makes it unique.

    Amino Acids as Acids and Bases

    • Amino acids contain both amino (-NH2) and carboxyl (-COOH) groups.
    • At physiological pH (~7.2), amino groups are protonated (-NH₃⁺) and carboxyl groups are deprotonated (-COO⁻).
    • This creates a zwitterion form (a dipolar ion) in solution, with a positive and a negative charge balancing each other.
    • The ionization of amino acids changes with pH.

    Isomers

    • Isomers are compounds with the same molecular formula but different structures.
    • Constitutional isomers have different atomic connectivities.
    • Stereoisomers have the same atomic connectivity but differ in spatial arrangement.
    • Enantiomers are non-superimposable mirror images, while diastereomers are not mirror images.
    • Chiral molecules have no plane of symmetry, and exist as enantiomers.

    Absolute Configuration

    • All amino acids except glycine are chiral.
    • Chiral amino acids exist as two non-superimposable mirror images called enantiomers and have different configurations denoted as D or L based on glyceraldehyde's configuration.
    • The absolute configuration is identified by the absolute configuration of the a-carbon determining the L or D isomer.

    Optical Activity

    • Chiral molecules (except glycine) can rotate plane-polarized light.
    • Dextrorotatory (+): rotations clockwise
    • Levorotatory (-): rotations counterclockwise
    • Specific rotation, a measure of a sample's optical activity, uses a polarimeter.

    Titration of Amino Acids

    • Amino acids are titrated using a strong base (like NaOH) to determine the effect of pH on net charge.
    • Different amino acids, with and without ionizable side chains, can be titrated to understand their pKa values for better prediction.

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    Amino Acids PDF

    Description

    Test your knowledge on amino acids, their functional groups, and configurations. This quiz covers key concepts like proline differences and the Fischer projection system. Perfect for students studying biochemistry or molecular biology.

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