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Questions and Answers
Which structural level of a protein is determined directly by the sequence of amino acids?
Which structural level of a protein is determined directly by the sequence of amino acids?
- Secondary structure
- Quaternary structure
- Primary structure (correct)
- Tertiary structure
What type of bond is primarily responsible for the formation of alpha-helices and beta-sheets in proteins?
What type of bond is primarily responsible for the formation of alpha-helices and beta-sheets in proteins?
- Van der Waals forces
- Hydrogen bonds (correct)
- Hydrophobic interactions
- Disulfide bonds
In the context of protein structure, what is the significance of a Ramachandran plot?
In the context of protein structure, what is the significance of a Ramachandran plot?
- It shows all possible amino acid sequences for a given protein.
- It predicts the rate of protein folding.
- It displays the possible phi and psi angles for amino acid residues. (correct)
- It helps identify the location of disulfide bridges.
Which of the following amino acids is most likely to cause a 'kink' or disruption in an alpha-helix structure?
Which of the following amino acids is most likely to cause a 'kink' or disruption in an alpha-helix structure?
What type of interaction is NOT typically involved in maintaining the tertiary structure of a protein?
What type of interaction is NOT typically involved in maintaining the tertiary structure of a protein?
Which of the following best describes the arrangement of beta-strands in an antiparallel beta-sheet?
Which of the following best describes the arrangement of beta-strands in an antiparallel beta-sheet?
What is the highest level of protein structure exhibited by hemoglobin, which consists of multiple polypeptide chains?
What is the highest level of protein structure exhibited by hemoglobin, which consists of multiple polypeptide chains?
Keratin, a structural protein found in hair and nails, primarily exhibits which type of secondary structure?
Keratin, a structural protein found in hair and nails, primarily exhibits which type of secondary structure?
Silk fibroin is characterized by which secondary structure motif?
Silk fibroin is characterized by which secondary structure motif?
Which of the following is NOT a typical force stabilizing quaternary structure in proteins?
Which of the following is NOT a typical force stabilizing quaternary structure in proteins?
Disulfide bonds are formed by the oxidation of which amino acid residue?
Disulfide bonds are formed by the oxidation of which amino acid residue?
What is the role of 'turns' or 'loops' in protein secondary structure?
What is the role of 'turns' or 'loops' in protein secondary structure?
Why are protein crystals sometimes grown in space (microgravity conditions)?
Why are protein crystals sometimes grown in space (microgravity conditions)?
Which method is a useful alternative to X-ray crystallography for determining protein structure?
Which method is a useful alternative to X-ray crystallography for determining protein structure?
What is a protein domain?
What is a protein domain?
What type of interactions contribute to the 'hydrophobic effect' in protein folding?
What type of interactions contribute to the 'hydrophobic effect' in protein folding?
What is the primary difference between parallel and antiparallel beta-sheets?
What is the primary difference between parallel and antiparallel beta-sheets?
Which statement is correct about alpha-helices?
Which statement is correct about alpha-helices?
How does the presence of a prosthetic group affect protein structure?
How does the presence of a prosthetic group affect protein structure?
Which of the following diseases is associated with a protein that can exist in multiple conformations, one of which is infectious?
Which of the following diseases is associated with a protein that can exist in multiple conformations, one of which is infectious?
Which type of interaction is most important for the association of two protein subunits in a homodimer?
Which type of interaction is most important for the association of two protein subunits in a homodimer?
What level of protein structure is characterized by the spatial arrangement of amino acid residues that are far apart in the primary structure?
What level of protein structure is characterized by the spatial arrangement of amino acid residues that are far apart in the primary structure?
How do chaperones assist in protein folding?
How do chaperones assist in protein folding?
Which component is NOT part of the repeating unit in the backbone of a protein?
Which component is NOT part of the repeating unit in the backbone of a protein?
Why is glycine frequently found in protein turns?
Why is glycine frequently found in protein turns?
Which of the following correctly describes the hydrogen bonding pattern in an alpha-helix?
Which of the following correctly describes the hydrogen bonding pattern in an alpha-helix?
Which of the following properties distinguishes a beta-barrel from a beta-sheet?
Which of the following properties distinguishes a beta-barrel from a beta-sheet?
Given the pentapeptide sequence Ser-Gly-Tyr-Ala-Leu, which terminus is represented by Ser?
Given the pentapeptide sequence Ser-Gly-Tyr-Ala-Leu, which terminus is represented by Ser?
Which technique relies on the analysis of diffraction patterns produced by protein crystals?
Which technique relies on the analysis of diffraction patterns produced by protein crystals?
Which of the following best explains why glycine exhibits more conformational freedom in a Ramachandran plot compared to other amino acids?
Which of the following best explains why glycine exhibits more conformational freedom in a Ramachandran plot compared to other amino acids?
What characterizes a protein consisting of all alpha domains?
What characterizes a protein consisting of all alpha domains?
What primarily holds multiple strands of amino acids together in quaternary protein structures?
What primarily holds multiple strands of amino acids together in quaternary protein structures?
Flashcards
Protein Primary Structure
Protein Primary Structure
The linear sequence of amino acids in a polypeptide chain, from the amino-terminal end to the carboxyl-terminal end.
Pentapeptide
Pentapeptide
A short sequence of amino acids linked together by peptide bonds, typically containing 5-15 amino acids.
Insulin
Insulin
A protein hormone with two polypeptide chains (A and B) linked by disulfide bonds, produced by the pancreas, regulating glucose levels in the blood.
Disulfide Bond
Disulfide Bond
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Protein Secondary Structure
Protein Secondary Structure
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Alpha-Keratin
Alpha-Keratin
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Alpha-Helix
Alpha-Helix
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Beta-Keratin
Beta-Keratin
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Beta-Sheet
Beta-Sheet
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Antiparallel Beta-Sheet
Antiparallel Beta-Sheet
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Parallel Beta-Sheet
Parallel Beta-Sheet
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Beta-Barrel
Beta-Barrel
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Beta Turns
Beta Turns
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Protein Tertiary Structure
Protein Tertiary Structure
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Myoglobin
Myoglobin
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Phi and Psi Angles
Phi and Psi Angles
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Proline
Proline
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Ramachandran Plot
Ramachandran Plot
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Quaternary Structure
Quaternary Structure
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Protein Renaturation
Protein Renaturation
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Prions
Prions
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Study Notes
- Protein structure is examined.
Protein Primary Structure
- Describes the amino acid sequence.
- A pentapeptide example is Ser-Gly-Tyr-Ala-Leu.
Insulin
- Depicts the structure of insulin.
- Displays intrachain and interchain disulfide bridges.
Disulphide Bonds in Hair
- Disulphide bonds are present in hair.
- They are reduced and oxidized to curl hair.
Protein Secondary Structure
- X-ray structures revealed alpha-helix and beta-sheet as the two main types.
- These structures are formed by hydrogen bonds between peptides.
Keratin
- Alpha-keratin (hair) has an alpha-helix structure.
- All protein alpha-helices are right-handed.
- Beta-keratin (silk) contains beta-sheets.
- Beta-sheets come in parallel and antiparallel varieties.
- Beta-barrels and twisted beta-sheets are other common secondary structures.
Linking Things Together
- The structure and arrangement of beta turns are represented, including Type I and Type II turns.
More Complex Proteins
- Max Perutz and Sir John Kendrew won the Nobel Prize in Chemistry in 1962.
- Sperm Whale Myoglobin exhibited the first globular protein diffraction pattern in 1958.
Growing Protein Crystals
- The best crystals of RNaseA were grown in space.
- Larger and better quality crystals are achieved due to microgravity and the absence of convection currents.
- NMR is a useful alternative to X-ray techniques of protein structure.
Classifying Peptide Conformations
- Classification of peptide conformations are shown.
Proline Problems
- Proline causes problems. -Proline isomers are shown.
Ramachandran Plots
- A Ramachandran Plot is illustrated for L-Ala.
- Common secondary structures occupy distinctive positions on Ramachandran plots.
- A Ramachandran diagram shows rabbit pyuvate kinase.
- Glycine positions are not shown, common practice in diagrams.
- Glycine (Gly) has more conformational freedom than other amino acids.
Protein Tertiary Structure
- Myoglobin contains several different alpha-helices.
- Packed together, these helices create a dense globular morphology.
- Van der Waals interactions, hydrophobic effects, electrostatic forces, and hydrogen bonds are commonly used.
Common Tertiary Structures
- Various common tertiary structures are presented.
Parallel Beta-Sheets
- Alpha/beta structures with parallel beta-sheets are represented.
Antiparallel Beta-Sheets
- Alpha+beta structures with antiparallel beta-sheets are represented.
Quaternary Structure
- Hemoglobin comprises 4 separate myoglobin-like strands.
- Each strand has a heme unit for transporting oxygen.
- These strands are held together by non-covalent forces.
Interactions
- Common interactions in proteins are shown.
Protein Denaturation
- Many proteins spontaneously regain their shape after denaturation.
Proteinaceous Infectious Proteins
- Proteinaceous infectious proteins (PrP or Prion) cause spongiform encephalopathies.
- Famous diseases include BSE, Scrapie, and CJD.
- No encoding is retrieved from nucleic acids like viruses, bacteria, and fungi.
Summary
- The primary structure is the amino acid residues
- The secondary structure is the alpha helix
- The tertiary structure is the polypeptide chain
- The quaternary structure is the assembled subunits
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