Biochemistry Chapter 4: Protein Structure

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Questions and Answers

Match the following terms related to protein structure with their corresponding definitions:

Primary structure = The linear sequence of amino acids in a polypeptide chain. Secondary structure = The local three-dimensional folding of a polypeptide chain, such as α-helices and β-sheets. Tertiary structure = The overall three-dimensional shape of a single polypeptide chain. Quaternary structure = The arrangement of multiple polypeptide chains (subunits) in a protein complex.

Match the following concepts about polypeptide chains with their appropriate descriptions:

Peptide bond = The covalent bond that links amino acids together in a polypeptide chain. Amino terminus = The end of a polypeptide chain that has a free amino group. Carboxyl terminus = The end of a polypeptide chain that has a free carboxyl group. Disulfide bond = A covalent bond that forms between two cysteine residues, linking different parts of a polypeptide chain or different polypeptide chains.

Match the following biological roles with their corresponding protein examples:

Receptor = A protein that binds to a specific molecule, triggering a cellular response. Enzyme = A protein that catalyzes a specific biochemical reaction. Structural protein = A protein that provides support and shape to cells and tissues. Hormone = A protein that acts as a chemical messenger, regulating physiological processes.

Match the following statements about protein structure with their corresponding levels of structure:

The sequence of amino acids in insulin = Primary structure The α-helix in a protein = Secondary structure The three-dimensional shape of an enzyme = Tertiary structure The arrangement of subunits in hemoglobin = Quaternary structure. Signup and view all the answers

Match the following features of amino acids with their roles in protein structure:

R-groups = Contribute to the unique properties and interactions of different amino acids. Side chains = Contribute to the overall three-dimensional shape of a protein by interacting with each other and with the environment. Polarity = Influences the solubility and interactions of amino acids within a protein. Hydrophobicity = Drives the folding of proteins into compact structures, often with hydrophobic residues buried in the interior. Signup and view all the answers

Match the following terms related to protein folding with their corresponding mechanisms:

Hydrogen bonding = Interactions between polar groups, contributing to the stability of secondary structures and tertiary structure. Hydrophobic interactions = Interactions between nonpolar groups, driving hydrophobic residues inwards in protein folding. Ionic interactions = Electrostatic attractions between charged groups, contributing to protein stability. Van der Waals interactions = Weak, short-range interactions between atoms, contributing to the overall shape and packing of proteins. Signup and view all the answers

Match the following factors influencing protein structure with their corresponding effects:

Temperature = Can disrupt weak interactions and cause protein denaturation. pH = Can alter the ionization state of amino acid side chains, affecting protein stability. Solvent = Can affect the solubility and stability of proteins through interactions with amino acid residues. Mutations = Can alter the sequence of amino acids, potentially affecting protein structure and function. Signup and view all the answers

Match the following statements about disulfide bonds with their appropriate descriptions:

Formation = Results from the oxidation of two cysteine residues. Location = Can occur between different parts of a polypeptide chain or different polypeptide chains. Role = Contribute to protein stability and structure by linking different regions together. Effect = Can affect protein conformation and function by stabilizing specific structures. Signup and view all the answers

Match the following types of secondary structure with their structural features:

α-Helix = A helical structure stabilized by hydrogen bonds between backbone atoms. β-Sheet = A sheet-like structure formed by hydrogen bonding between polypeptide chains. Coiled Coil = Two α-helices intertwined to form a left-handed superhelix. Triple Helix = Three intertwined helical polypeptide chains forming a superhelical cable. Signup and view all the answers

Match the structural features of peptide bonds with their corresponding properties.

Planarity = Due to partial double bond character Trans configuration = Minimizes steric clashes between side chains Cis configuration = Rarely observed due to steric hindrance Proline = Disrupts helix formation due to its rigid ring structure Signup and view all the answers

Match the following types of protein interactions with their descriptions:

Hydrogen Bonds = Interactions between polar groups, involving a hydrogen atom shared between two electronegative atoms. Ionic Bonds = Interactions between oppositely charged groups. Van Der Waals Forces = Weak attractions between nonpolar molecules. Disulfide Bonds = Covalent bonds between sulfur atoms in cysteine residues. Signup and view all the answers

Match the types of secondary structures with their defining characteristics.

Alpha helix = A coiled structure stabilized by intrachain hydrogen bonds Beta sheet = A sheet-like structure formed by hydrogen bonds between adjacent strands Turn = A sharp bend in the polypeptide chain, often involving proline Random coil = A region without a defined structure Signup and view all the answers

Match the following types of protein structures with their levels of organization:

Primary Structure = The linear sequence of amino acids in a polypeptide chain. Secondary Structure = The local three-dimensional arrangement of amino acids, such as α-helices and β-sheets. Tertiary Structure = The overall three-dimensional shape of a single polypeptide chain. Quaternary Structure = The arrangement of multiple polypeptide chains (subunits) in a protein complex. Signup and view all the answers

Match the following proteins with their primary functions:

α-Keratin = Structural protein found in hair, wool, and nails. Collagen = Structural protein found in skin, bone, tendons, and cartilage. Myoglobin = Oxygen-binding protein in muscle tissue. Hemoglobin = Oxygen-binding protein in red blood cells. Signup and view all the answers

Match the amino acid residues with their effects on alpha helix stability.

Valine, Threonine, Isoleucine = Steric clashes destabilize the helix Serine, Aspartic acid, Asparagine = Hydrogen bonding interactions destabilize the helix Proline = Ring structure prevents bond rotation, disrupting helix formation Glycine = Small size allows for flexibility, potentially stabilizing the helix Signup and view all the answers

Match the features of beta sheets with their descriptions.

Parallel = Adjacent strands run in the same direction (N-terminus to C-terminus) Antiparallel = Adjacent strands run in opposite directions Mixed = A combination of parallel and antiparallel strands Twisted conformation = A common structural variation of the beta sheet Signup and view all the answers

Match the following structural features with their descriptions:

Turns and Loops = Regions of polypeptide chains that change direction, often involved in protein interactions. Fibrous Proteins = Proteins with elongated, thread-like structures, providing structural support. Globular Proteins = Proteins with compact, spherical structures, often involved in enzymatic activity or signaling. Coiled Coil = A superhelical structure formed by two intertwined α-helices, often found in fibrous proteins. Signup and view all the answers

Match the types of hydrogen bonding in protein structures with their relevant locations.

Intrachain hydrogen bonds = Stabilize alpha helices Interchain hydrogen bonds = Stabilize beta sheets Hydrogen bonds between side chains = Contribute to tertiary and quaternary structure Hydrogen bonds involving backbone atoms = Primary contributors to secondary structure Signup and view all the answers

Match the following terms related to protein structure with their definitions:

Superhelix = A helical structure formed by the intertwining of multiple polypeptide chains. Disulfide Bond = A covalent bond between sulfur atoms in cysteine residues, stabilizing protein structure. Salt Bridge = An ionic interaction between oppositely charged groups, contributing to protein stability. Hydrophobic Interaction = Nonpolar interactions between amino acids, driving protein folding. Signup and view all the answers

Match the biological phenomena with their corresponding roles in protein structure.

Hydrophobic interactions = Drive the folding of proteins into compact structures Disulfide bonds = Stabilize tertiary and quaternary structure, particularly in extracellular proteins Electrostatic interactions = Contribute to the stability of protein-protein interactions and other interactions Van der Waals forces = Weak interactions that contribute to overall protein stability Signup and view all the answers

Match the following features of protein structure with their roles in protein stability:

Hydrogen Bonding = Stabilizes secondary structure by interacting with backbone atoms. Hydrophobic Interactions = Drives the burial of nonpolar residues in the protein interior. Disulfide Bonds = Forms covalent cross-links, stabilizing tertiary structure. Ionic Interactions = Contributes to protein stability by forming salt bridges between oppositely charged groups. Signup and view all the answers

Match the levels of protein structure with their defining characteristics.

Primary structure = The linear sequence of amino acids in a polypeptide chain Secondary structure = Local three-dimensional structures formed by hydrogen bonding between backbone atoms Tertiary structure = The overall three-dimensional shape of a single polypeptide chain Quaternary structure = The arrangement of multiple polypeptide chains in a protein complex Signup and view all the answers

Match the following types of amino acids with their typical locations in globular proteins:

Hydrophobic Amino Acids = Found primarily in the interior of globular proteins, away from water. Polar Amino Acids = Found on the exterior of globular proteins, interacting with water. Charged Amino Acids = Found on the surface of globular proteins, contributing to protein-protein interactions. Signup and view all the answers

Match the factors that influence protein stability with their effects.

Temperature = High temperatures can disrupt hydrogen bonding and other weak interactions, leading to denaturation pH = Extreme pH values can disrupt electrostatic interactions and alter the ionization state of amino acids Salt concentration = High salt concentrations can shield electrostatic interactions, potentially destabilizing proteins Presence of denaturants = Substances like urea and guanidinium hydrochloride can disrupt hydrogen bonding and hydrophobic interactions, causing unfolding Signup and view all the answers

Match the following structural levels of a protein with their corresponding descriptions:

Primary structure = The linear sequence of amino acids in a polypeptide chain. Secondary structure = Regular, repeating patterns of amino acid chains, such as alpha-helices and beta-sheets. Tertiary structure = The three-dimensional shape of a single polypeptide chain, incorporating interactions between side chains. Quaternary structure = The arrangement of multiple polypeptide chains in a protein complex. Signup and view all the answers

Match the following protein structures with their corresponding examples:

Motifs = A combination of secondary structures, like a helix-turn-helix motif in DNA-binding proteins. Domains = Distinct, compact regions within a protein, often with specific functions, like a catalytic domain in an enzyme. Subunits = Individual polypeptide chains that associate to form a multimeric protein, like the subunits of hemoglobin. Quaternary structure = The arrangement of multiple subunits in a protein complex, like the tetrameric structure of hemoglobin. Signup and view all the answers

Match the following agents with their effects on protein structure:

Urea = Disrupts non-covalent interactions, like hydrogen bonds and hydrophobic interactions. Mercaptoethanol = Reduces disulfide bonds, breaking covalent links between cysteine residues. Heat = Disrupts non-covalent interactions, causing unfolding and loss of structure. pH changes = Can disrupt ionic interactions and hydrogen bonds, leading to protein denaturation. Signup and view all the answers

Match the following aspects of protein folding with their corresponding descriptions:

Hydrophobic effect = The tendency of nonpolar amino acid side chains to cluster away from water, driving protein folding. Folding funnel = A conceptual model illustrating how proteins fold, with a landscape of energy states leading to the native, lowest-energy conformation. Anfinsen experiment = Demonstrated that the amino acid sequence of a protein determines its three-dimensional structure. Chaperone proteins = Assist in protein folding by preventing aggregation and promoting proper conformation. Signup and view all the answers

Match the following characteristics with their corresponding impact on protein structure:

Nonpolar amino acids = Tend to be found in the interior of a protein, away from water. Polar amino acids = Often found on the surface of a protein, interacting with water. Disulfide bonds = Covalent bonds that stabilize the tertiary structure, particularly in proteins that encounter harsh environments. Hydrogen bonds = Non-covalent interactions that contribute to both secondary and tertiary structures, often between polar side chains. Signup and view all the answers

Flashcards

Peptide Bond

A bond linking amino acids in a polypeptide chain, also known as amide bond.

Polypeptide Chain Directionality

Polypeptide chains have a defined direction from amino terminal to carboxyl terminal.