Amino Acids & Proteins Quiz
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Questions and Answers

Which of the following amino acids are classified as aromatic?

  • Leucine, Isoleucine, Alanine, Valine
  • Threonine, Serine
  • Phenylalanine, Tryptophan, Tyrosine (correct)
  • Cysteine, Methionine

    • Which of the following amino acids can be classified as acidic?

  • Asparagine, Glutamine
  • Lysine, Arginine, Histidine
  • Proline
  • Aspartic acid, Glutamic acid (correct)

    • What is the primary structure of a protein?

  • The three-dimensional shape of a protein.
  • The arrangement of protein subunits.
  • The interactions between polypeptide chains.
  • The linear sequence of amino acids in a protein. (correct)

    • Which type of amino acid is most likely to be soluble in water?

    <p>Polar and uncharged amino acids (C)</p> Signup and view all the answers

    Which of the following statements is TRUE about proteins?

    <p>The size of a protein is a major factor influencing its function. (B)</p> Signup and view all the answers

    Which of the following amino acids contains sulfur?

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

    Which of the following best describes the functional role of proteins?

    <p>Proteins carry out a wide range of functions, including catalysis, transport, and structural support. (C)</p> Signup and view all the answers

    Which of the following types of amino acids is characterized by a cyclic side chain?

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

    Which of the following interactions is responsible for the spontaneous avoidance of water by hydrophobic side chains?

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

    What type of interaction contributes to the formation of temporary dipoles between methyl groups?

    <p>Van der Waals interactions (B)</p> Signup and view all the answers

    Which of the following statements best describes the role of the peptide bond in protein structure?

    <p>The peptide bond restricts the free rotation of amino acids, enabling the formation of specific protein structures. (D)</p> Signup and view all the answers

    What is the primary difference between the quaternary structure of muscle creatine kinase and hemoglobin?

    <p>Muscle creatine kinase has identical subunits while hemoglobin has different subunits. (D)</p> Signup and view all the answers

    Which of the following interactions is NOT directly involved in stabilizing the tertiary structure of a protein?

    <p>Ionic bonds between adjacent polypeptide chains (A)</p> Signup and view all the answers

    Which of the following correctly describes the supersecondary structure of a protein?

    <p>The specific arrangement of secondary structures, such as alpha helices and beta sheets, within a protein. (A)</p> Signup and view all the answers

    What is the major difference between alpha helices and beta sheets in terms of their structure?

    <p>Alpha helices have a helical structure with a right-handed twist, while beta sheets have a planar, sheet-like structure. (D)</p> Signup and view all the answers

    Which of the following amino acids are typically found in the interior of globular proteins?

    <p>Valine (Val), leucine (Leu), methionine (Met) (C)</p> Signup and view all the answers

    Which of the following describes a protein domain?

    <p>A small, independent unit of protein structure that often has a specific function. (D)</p> Signup and view all the answers

    Which of the following proteins has a high proportion of alpha helices and is involved in oxygen transport?

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

    What type of interaction is primarily responsible for stabilizing the tertiary structure of a protein?

    <p>All of the above (D)</p> Signup and view all the answers

    Which statement BEST describes the relationship between protein structure and function?

    <p>A protein's function is determined by its tertiary structure, the three-dimensional folding pattern. (C)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the beta-pleated sheet structure in proteins?

    <p>It is a highly flexible structure that allows for easy bending and twisting. (A)</p> Signup and view all the answers

    Flashcards

    Amino Acid

    Basic unit of a protein, building blocks.

    R Group Classification

    Classifies amino acids based on chemical properties of R group.

    Hydrophobic Amino Acids

    Amino acids that are non-polar and repel water.

    Zwitterions

    Amino acids with both positive and negative charges.

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    Protein Structure

    Order and arrangement of amino acids in a protein.

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    Globular Proteins

    Proteins that are spherical and soluble in water.

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    Fibrous Proteins

    Structural proteins with long, thread-like shapes.

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    Conjugated Proteins

    Proteins with a non-protein component attached.

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    Peptide bond rotation

    The rotation around peptide bonds is limited due to their double bond characteristics.

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    Hydrophobic interactions

    Forces between hydrophobic side chains that minimize water interaction, stabilizing protein structure.

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    Electrostatic interactions

    Attractions between charged side chains, such as COO- and NH+ groups in proteins.

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    Van der Waals interactions

    Weak attractions due to fluctuating electron clouds forming temporary dipoles.

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    Quaternary structure

    The level of protein structure formed by the association of multiple polypeptide chains or subunits.

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    Secondary Structure

    Local conformations of a polypeptide chain formed by hydrogen bonding between backbone atoms.

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    Super Secondary Structures

    Specific arrangements of secondary structures in proteins.

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    Tertiary Structure

    The 3D structure of a protein formed by interactions between distant amino acids.

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    α-Helix

    A right-handed coil formed by repeated hydrogen bonding in a protein structure.

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    β-Structure

    A sheet-like structure formed by hydrogen bonds, existing in parallel or anti-parallel arrangements.

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    Peptide Bond

    A covalent bond between the C=O and N-H groups in a protein, which is planar.

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    Study Notes

    Amino Acids & Proteins

    • Amino acids are the basic units of proteins.
    • Amino acids have a central carbon atom (α-carbon) bonded to an amino group (-NH3+), a carboxyl group (-COO-), a hydrogen atom, and a variable side chain (R-group).
    • The R-group determines the specific properties of each amino acid.
    • Stereoisomerism exists (D/L): L-amino acids are biologically important.
    • Amino acids are classified based on the chemical properties of their R-groups (polar/nonpolar, acidic/basic).
    • Examples of classifications include aliphatic, aromatic, sulfur-containing, and those with hydroxyl groups, acidic, basic and imino acids.
    • Specific examples of amino acids were provided (including: Leu, Pro, Ala, Val; Phe, Trp, Tyr; Cys, Met; Thr, Ser; Asp, Glu; Lys, Arg, His; Pro; Gln, Asn).
    • Proteins are biopolymers of amino acids. They can vary greatly in size (100-2,000+ amino acids).
    • Some examples of proteins include myoglobin (153 aa), ADH (374 aa), and hemoglobin (574 aa) along with insulin (51 aa) and collagen.
    • Two main classes of proteins are globular and fibrous.
    • Proteins can act as enzymes, structural components, or for transport, and as hormones.
    • Conjugated proteins also exist, which have non-protein moieties.
    • Some properties of amino acids are discussed in the document.
    • Amino acids are typically soluble in polar solvents (e.g. water) but not in organic solvents
    • Amino acids have high melting points due to their crystalline structure and charged polar groups.
    • Aromatic amino acids absorb UV light due to conjugated double bonds in their R groups, which can be used to detect them.
    • Amino acids can be amphoteric (with both positive and negative charges) and called zwitterions, the charge can be affected by pH

    Protein Structure

    • Primary structure: The linear sequence of amino acids in a protein.
    • Secondary structure: The local conformations (alpha helix and beta sheet) formed by hydrogen bonding between polypeptide backbone atoms.
    • Super Secondary Structures: Secondary structures arranged in a specific manner (motifs).
    • Tertiary Structure: The overall 3-dimensional structure, determined by interactions between amino acids far apart in the primary sequence.
    • Quaternary structure: The association of multiple polypeptide chains (subunits) in a protein.

    Secondary Protein Structures

    • α-helix: A common secondary structure stabilized by hydrogen bonds between the carbonyl oxygen and the amide hydrogen of every fourth amino acid. Commonly right-handed and ~3.6 amino acids/turn, with roughly 11 aa per turn (in a globular protein)
    • β-sheet: Another common secondary structure involving hydrogen bonds between adjacent polypeptide strands, that may be parallel or anti-parallel. Usually 2-15 amino acids (avg=6) per beta sheet.

    Tertiary Protein Structures

    • The 3-dimensional structure of a protein/polypeptide
    • Super secondary structures/motifs can be involved
    • On average, roughly 27% in alpha, 23% in beta (myoglobin/hemoglobin has greater proportion of alpha helices) are common in some proteins.
    • There are instances of exceptions like Concanavalin A which has beta structures without alpha helices
    • Hydrophobic amino acids tend to be in the core of a globular protein, whilst polar amino acids on the surface.

    Forces That Influence Protein Structure

    • Peptide bond geometry: The C=O and C-N bonds are planar, affecting rotation and structure.
    • Hydrogen bonds: Occur between the carbonyl oxygen and amide hydrogen of the peptide backbone.
    • Hydrophobic interactions: Nonpolar amino acid side chains cluster together in the protein interior to avoid water.
    • Electrostatic interactions: Occur between charged amino acid side chains (e.g., ionic bonds).
    • Van der Waals interactions (dipole-dipole): Weak attractions between atoms or molecules.
    • Disulfide bonds: Covalent bonds between cysteine residues in the protein, forming cross-links.

    Quaternary Structures

    • The fourth level, interaction between two or more polypeptide chains to form a larger protein
    • Oligomeric proteins composed of subunits.
    • Homogenous/heterogeneous types of subunit arrangement.
    • Dimer, trimer, tetramer etc are common designations of subunit arrangement (e.g. Haemoglobin is a tetramer with both alpha and beta subunits present).

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    Basic and General Biochemistry Amino Acid and Protein PDF

    Description

    Test your understanding of amino acids and proteins with this quiz. Explore the structure, classification, and biological significance of amino acids, along with examples of proteins. Perfect for students studying biochemistry or related fields.

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