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Questions and Answers
Which of the following bonds primarily stabilize the tertiary structure of proteins?
Which of the following bonds primarily stabilize the tertiary structure of proteins?
What characterizes the quaternary structure of proteins?
What characterizes the quaternary structure of proteins?
Which of the following is NOT a common type of post-translational modification of proteins?
Which of the following is NOT a common type of post-translational modification of proteins?
What are protein domains primarily responsible for?
What are protein domains primarily responsible for?
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Which of the following best describes super-secondary structures in proteins?
Which of the following best describes super-secondary structures in proteins?
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How do hydrogen bonds influence protein stability?
How do hydrogen bonds influence protein stability?
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In which scenario would an abnormal protein structure likely lead to disease?
In which scenario would an abnormal protein structure likely lead to disease?
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Which structure enables proteins to cross lipid membranes?
Which structure enables proteins to cross lipid membranes?
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Which amino acid is involved in forming disulfide bonds in protein structures?
Which amino acid is involved in forming disulfide bonds in protein structures?
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Which level of protein structure is directly determined by the sequence of amino acids?
Which level of protein structure is directly determined by the sequence of amino acids?
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What type of secondary structure is characterized by hydrogen bonds forming between co-planar β-pleats?
What type of secondary structure is characterized by hydrogen bonds forming between co-planar β-pleats?
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What main interactions stabilize the tertiary structure of a protein?
What main interactions stabilize the tertiary structure of a protein?
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Which modification can directly alter the tertiary structure of proteins by adding functional groups?
Which modification can directly alter the tertiary structure of proteins by adding functional groups?
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How does a protein domain differ from secondary structures like motifs?
How does a protein domain differ from secondary structures like motifs?
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Which of the following is the most common super-secondary structure found in proteins?
Which of the following is the most common super-secondary structure found in proteins?
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What role do chaperone proteins play in protein folding?
What role do chaperone proteins play in protein folding?
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What type of bond is primarily responsible for holding the three α-polypeptides together in the triple helix of collagen?
What type of bond is primarily responsible for holding the three α-polypeptides together in the triple helix of collagen?
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What is the final form of a protein that consists of multiple polypeptide chains referred to as?
What is the final form of a protein that consists of multiple polypeptide chains referred to as?
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Which amino acid substitution in the β-chain of hemoglobin is responsible for the structural changes leading to sickle cell anemia?
Which amino acid substitution in the β-chain of hemoglobin is responsible for the structural changes leading to sickle cell anemia?
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What structure is formed when helices and sheets combine into compact arrangements?
What structure is formed when helices and sheets combine into compact arrangements?
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Which of the following is NOT a characteristic of fibrous proteins?
Which of the following is NOT a characteristic of fibrous proteins?
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Which term describes the non-repetitive structures such as turns, coils, and loops found in proteins?
Which term describes the non-repetitive structures such as turns, coils, and loops found in proteins?
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The process that requires energy to assist with proper folding of proteins is facilitated by which molecules?
The process that requires energy to assist with proper folding of proteins is facilitated by which molecules?
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What is the primary function of collagen in the body?
What is the primary function of collagen in the body?
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Which of the following amino acids is frequently found in the X position of the (Gly-X-Y) repeat in collagen?
Which of the following amino acids is frequently found in the X position of the (Gly-X-Y) repeat in collagen?
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What is the role of vitamin C in collagen synthesis?
What is the role of vitamin C in collagen synthesis?
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Which of the following is an example of a super-secondary structure in proteins?
Which of the following is an example of a super-secondary structure in proteins?
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The change in the tertiary structure of the β-subunit in sickle cell anemia is primarily due to:
The change in the tertiary structure of the β-subunit in sickle cell anemia is primarily due to:
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Study Notes
Protein Structure and Folding
- Post-translational Modification: Protein structure can be significantly altered after translation through modifications like phosphorylation and glycosylation.
Secondary Structure
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Peptide Folding: H-bonding in the peptide backbone creates a repetitive folding pattern leading to structures such as α-helix and β-sheet.
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Random Coil: Represents an undefined and irregular secondary structure without a stable 3D conformation.
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Beta (β-) Sheet: Stabilized by hydrogen bonds that are co-planar with the β-pleat, with R groups alternating above and below the plane.
Super Secondary Structures (Motifs)
- Motifs: Combination of secondary structures in globular proteins; recognizes patterns across multiple proteins.
- Common Motif: αβ motif is one of the most prevalent super-secondary structures.
- Non-repetitive Structures: Includes turns, coils, and loops that serve unique functions.
Tertiary Structure
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3D Conformation: The final folded state of a polypeptide, stabilized by various interactions:
- Hydrophobic Interactions: Attraction between closely packed nonpolar groups.
- Hydrogen Bonds: Interactions between proton donors and acceptors.
- Ionic Interactions: Charged groups interact through salt-bridges.
- Disulfide Bonds: Formed by the oxidation of sulfhydryl groups.
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Protein Shapes: Tertiary structures can be fibrous or globular, with polar amino acids generally on the periphery.
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Post-Translational Folding Impact: Modifications can affect overall folding and protein function.
Protein Domains
- Defining Units: Functional and structural units within a polypeptide, often comprising one or more super-secondary structures.
- Independent Folding: Each domain can fold independently and can evolve or function on its own.
Protein Folding and Chaperones
- Energy Requirement: Protein folding requires energy and is assisted by chaperone proteins which aid in proper assembly and refolding of polypeptide chains.
- Role of ATP: ATP is necessary for facilitating interactions during folding and translocation.
Quaternary Structure
- Polypeptide Assembly: Involves multiple polypeptide chains forming a supramolecular complex; characterized by the prefix indicating the number of subunits (e.g., dimeric, trimeric).
Levels of Protein Structure
- Primary Structure: Linear sequence of amino acids linked by peptide bonds; determines 3D folding.
- Peptide Bonds: Formed by a condensation reaction, exhibiting restricted rotation, contributing to rigidity and planarity.
Amino Acid Properties
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Classification: Includes:
- Nonpolar Aliphatic: Gly, Ala, Ile, Leu, Val, Phe, Trp, Met, Pro.
- Basic: Arg, Lys, His.
- Acidic: Asp, Glu.
- Polar Uncharged: Asn, Gln, Ser, Thr, Tyr, Cys.
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Optical Properties: Only L-amino acids are standard; UV absorbance varies by aromatic amino acids.
Protein Misfolding and Disease
- Consequences of Misfolding: Altered protein structures can disrupt normal function, as seen in sickle cell anemia.
- Sickle Cell Example: A mutation in the β chain of hemoglobin modifies the quaternary structure and impacts hemoglobin functionality.
Fibrous Proteins
- Characteristics: Typically elongated and rigid, providing structural support within biological systems; highly enriched with specific amino acids.
- Collagen: Most abundant protein in the body, forms a triple helix structure providing tensile strength and support.
Collagen Synthesis
- Primary Structure: Characterized by repeating motifs of (Gly-X-Y), with X generally being proline and Y hydroxyproline or hydroxylysine.
- Vitamin C Role: Essential for hydroxylation of proline and lysine, aiding in stable collagen structure formation.
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Description
This quiz covers the different aspects of protein structure, including post-translational modification, secondary structure, and folding patterns. It explores how proteins are altered after translation and the different types of secondary structures that can form.
