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Questions and Answers
What type of protein structure is altered in sickle cell anemia?
What type of protein structure is altered in sickle cell anemia?
What is the function of fibrous proteins in the body?
What is the function of fibrous proteins in the body?
What type of bonds hold α chains together in collagen?
What type of bonds hold α chains together in collagen?
What is the function of vitamin C in collagen synthesis?
What is the function of vitamin C in collagen synthesis?
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What is the primary structure of collagen?
What is the primary structure of collagen?
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What is the effect of the mutation in sickle cell anemia on hemoglobin?
What is the effect of the mutation in sickle cell anemia on hemoglobin?
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What is the function of proline and hydroxyproline in collagen?
What is the function of proline and hydroxyproline in collagen?
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What is the structure of collagen fibrils?
What is the structure of collagen fibrils?
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What primarily stabilizes the secondary structure of proteins?
What primarily stabilizes the secondary structure of proteins?
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Which statement best describes a characteristic of tertiary protein structure?
Which statement best describes a characteristic of tertiary protein structure?
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What role do hydrophobic interactions play in protein folding?
What role do hydrophobic interactions play in protein folding?
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Which factor is NOT typically involved in protein folding pathways?
Which factor is NOT typically involved in protein folding pathways?
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What is a defining feature of a protein domain?
What is a defining feature of a protein domain?
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Which type of protein generally exhibits a quaternary structure?
Which type of protein generally exhibits a quaternary structure?
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Which of the following amino acid types is characterized by its ability to form hydrogen bonds in secondary structures?
Which of the following amino acid types is characterized by its ability to form hydrogen bonds in secondary structures?
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In the context of protein interactions, what is typically the result of hydrophilic and hydrophobic side chain distributions?
In the context of protein interactions, what is typically the result of hydrophilic and hydrophobic side chain distributions?
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Which property must a protein possess to function correctly in its quaternary structure?
Which property must a protein possess to function correctly in its quaternary structure?
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What impact does abnormal protein structure typically have on cellular function?
What impact does abnormal protein structure typically have on cellular function?
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Which of the following statements accurately describes the role of hydrophobic interactions in tertiary protein structure?
Which of the following statements accurately describes the role of hydrophobic interactions in tertiary protein structure?
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What is the primary difference between a super-secondary structure (motif) and a protein domain?
What is the primary difference between a super-secondary structure (motif) and a protein domain?
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Which of the following statements accurately describes the relationship between primary structure and tertiary structure?
Which of the following statements accurately describes the relationship between primary structure and tertiary structure?
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How do chaperone proteins contribute to protein folding?
How do chaperone proteins contribute to protein folding?
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Which of the following statements accurately describes the role of disulfide bonds in tertiary structure?
Which of the following statements accurately describes the role of disulfide bonds in tertiary structure?
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Why is protein folding a complex process that often requires chaperone proteins?
Why is protein folding a complex process that often requires chaperone proteins?
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Which of the following is NOT a common feature of protein domains?
Which of the following is NOT a common feature of protein domains?
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How do the R groups of amino acids contribute to the formation of beta-sheets?
How do the R groups of amino acids contribute to the formation of beta-sheets?
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Which of the following statements accurately describes the concept of a "random coil" in protein structure?
Which of the following statements accurately describes the concept of a "random coil" in protein structure?
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How does the tertiary structure of a protein contribute to its function?
How does the tertiary structure of a protein contribute to its function?
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Study Notes
Protein Structure and Function
- Proteins have different levels of structure, including primary, secondary, tertiary, and quaternary structures, each stabilized by specific forces.
- Primary structure: the linear sequence of amino acid residues joined through peptide bonds, determining the 3D structure of a polypeptide.
- Peptide bonds: formed through condensation reactions between α-carboxylate and α-amino groups, with characteristics that affect protein structure, such as restricted rotation and resonance.
- Chemical nature of amino acids: classified into aliphatic, non-aromatic with hydroxyl R-groups, sulfur-containing, acidic, basic, aromatic, imino, and other groups.
Primary Structure
- Nonpolar (aliphatic) side groups: gly, ala, ile, leu, val, met, and pro.
- Side chains with basic groups: arg, lys, and his.
- Side chains with acidic groups: asp and glu.
- Polar but uncharged groups: amide derivatives of asp and glu (asn and gln), hydroxyl groups (ser, thr, and tyr), and sulfhydryl groups (cys).
- Other classifications: hydrophilic vs hydrophobic, optical properties, essential vs non-essential, and glucogenic vs ketogenic or ketogenic/glucogenic.
Secondary Structure
- H-bonding of peptide backbone causes amino acids to fold into a repeating pattern, forming common structures like α-helix and β-sheet.
- β-sheet: stabilized by hydrogen bonds co-planar with the β-pleat, with R groups alternating above and below the plane.
- Super secondary structures (motifs): combining secondary structural elements, such as the αβ motif, to form globular proteins.
Tertiary Structure
- Final folded state of a complete polypeptide in 3D conformation, stabilized by hydrophobic interactions, hydrogen bonding, ionic interactions, and disulfide bond formation.
- Creates specific and flexible binding sites for ligands and maintains an appropriate surface for the protein's cellular location.
- Folding can be affected by post-translational modifications of amino acids, such as phosphorylation, glycosylation, and acetylation.
Protein Domains
- Fundamental functional and three-dimensional structural unit(s) of a polypeptide, comprising one or more super-secondary structures.
- Folding of a domain usually occurs independently of folding in other domains.
- A domain is a conserved part of a given full-length protein sequence, with a defined tertiary structure that can evolve, function, and exist independently of the rest of the protein chain.
Protein Folding and Quaternary Structure
- Protein folding requires energy and is assisted by chaperone proteins, which protect and guide the proper folding of nascent polypeptide chains.
- Quaternary structure: multiple polypeptide chains (or subunits) assembled into a supramolecular complex, with a specific number of subunits designated by a prefix (e.g., dimeric, trimeric).
- May consist of identical (homopolymeric) or different (heteropolymeric) subunits.
Protein Misfolding and Function
- Protein misfolding alters normal function and interactions of proteins, as seen in sickle cell anemia, where a mutation in the β chain changes the quaternary structure of hemoglobin.
Fibrous Proteins
- Elongated, rigid proteins enriched in specific amino acids and unique secondary structures, serving structural functions in the body.
- Examples: collagen, which provides tensile strength, with a superfamily of extracellular matrix proteins.
Collagen
- Most abundant protein in the body, with a triple helix of three α-polypeptides wound around each other.
- Primary structure: polymer of (Gly-X-Y) repeats, where X is frequently proline and Y is often hydroxyproline (or hydroxylysine).
- Vitamin C is required as a cofactor for the hydroxylation of Pro and Lys.
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Description
Explore the different levels of protein structure, including primary, secondary, tertiary, and quaternary structures, and learn how they are stabilized by specific forces.
