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Questions and Answers
What does the 1° structure of a protein refer to?
What does the 1° structure of a protein refer to?
- The quaternary structure of a protein
- The local conformations of a protein
- The sequence of amino acids in a polypeptide chain (correct)
- The 3D conformation of a protein
What type of bonds are involved in the formation of α-helices?
What type of bonds are involved in the formation of α-helices?
- Ionic bonds
- Disulfide bonds
- Hydrogen bonds (correct)
- Peptide bonds
Which of the following is a characteristic of α-helices?
Which of the following is a characteristic of α-helices?
- Random coil structure
- Helical structure (correct)
- β-turns
- Extended flat sheets
What is the direction of the hydrogen bonds in an α-helix?
What is the direction of the hydrogen bonds in an α-helix?
Which two bonds have free rotation in a protein?
Which two bonds have free rotation in a protein?
What is the type of structure that involves extended, flat sheets?
What is the type of structure that involves extended, flat sheets?
How many amino acids down the chain does the C=O of one amino acid hydrogen bond to in an α-helix?
How many amino acids down the chain does the C=O of one amino acid hydrogen bond to in an α-helix?
What is the average number of amino acids in each turn of the α-helix?
What is the average number of amino acids in each turn of the α-helix?
What is the secondary structure element that involves a regular pattern of hydrogen bonds between amide N-H and C=O groups?
What is the secondary structure element that involves a regular pattern of hydrogen bonds between amide N-H and C=O groups?
Why does proline create a bend in the α-helix structure?
Why does proline create a bend in the α-helix structure?
What is the main difference between globular and fibrous proteins?
What is the main difference between globular and fibrous proteins?
What is the term for the local conformations maintained by extensive hydrogen bonding in a protein?
What is the term for the local conformations maintained by extensive hydrogen bonding in a protein?
Which of the following is NOT a type of secondary structure?
Which of the following is NOT a type of secondary structure?
What is the term for the association of polypeptide chains?
What is the term for the association of polypeptide chains?
What is the effect of the presence of BPG on hemoglobin's affinity for oxygen?
What is the effect of the presence of BPG on hemoglobin's affinity for oxygen?
What is the purpose of hemoglobin in the blood?
What is the purpose of hemoglobin in the blood?
What is the main cause of denaturation?
What is the main cause of denaturation?
What is the result of heat-induced denaturation of proteins?
What is the result of heat-induced denaturation of proteins?
What is the effect of 2,3BPG on hemoglobin?
What is the effect of 2,3BPG on hemoglobin?
What is the term for the change in the oxygen binding behavior of hemoglobin in response to changes in pH and CO2 levels?
What is the term for the change in the oxygen binding behavior of hemoglobin in response to changes in pH and CO2 levels?
What is the function of molecular chaperones?
What is the function of molecular chaperones?
What is the term for the structure of a protein that has a native-like secondary structure content but without tightly packed protein interior?
What is the term for the structure of a protein that has a native-like secondary structure content but without tightly packed protein interior?
What is the main difference between the oxygen binding curves of myoglobin and hemoglobin?
What is the main difference between the oxygen binding curves of myoglobin and hemoglobin?
What is the function of the R groups in the α-helix structure?
What is the function of the R groups in the α-helix structure?
What is the main role of hydrophobic effect in protein folding?
What is the main role of hydrophobic effect in protein folding?
Why do globular proteins tend to have a higher proportion of polar side chains on the outside?
Why do globular proteins tend to have a higher proportion of polar side chains on the outside?
What is the consequence of errors in protein folding?
What is the consequence of errors in protein folding?
What is the location of hydrophobic residues in globular proteins?
What is the location of hydrophobic residues in globular proteins?
What is the role of chaperones in protein folding?
What is the role of chaperones in protein folding?
What is the strategy used by chaperones to guide misfolded regions back into place?
What is the strategy used by chaperones to guide misfolded regions back into place?
What refers to the linear amino acid sequence from the N-terminal end to the C-terminal end?
What refers to the linear amino acid sequence from the N-terminal end to the C-terminal end?
What type of bonds are involved in the formation of α-helices?
What type of bonds are involved in the formation of α-helices?
What is the characteristic of α-helices in terms of hydrogen bonding?
What is the characteristic of α-helices in terms of hydrogen bonding?
Which bonds have free rotation in a protein?
Which bonds have free rotation in a protein?
What is the term for local conformations maintained by extensive hydrogen bonding in a protein?
What is the term for local conformations maintained by extensive hydrogen bonding in a protein?
What type of structure involves extended, flat sheets?
What type of structure involves extended, flat sheets?
What is the consequence of errors in protein folding?
What is the consequence of errors in protein folding?
How many amino acids down the chain does the C=O of one amino acid hydrogen bond to in an α-helix?
How many amino acids down the chain does the C=O of one amino acid hydrogen bond to in an α-helix?
What is the direction of the hydrogen bonds in an α-helix?
What is the direction of the hydrogen bonds in an α-helix?
What is the secondary structure element that involves a regular pattern of hydrogen bonds between amide N-H and C=O groups?
What is the secondary structure element that involves a regular pattern of hydrogen bonds between amide N-H and C=O groups?
What is the main reason for the decrease in hemoglobin's affinity for oxygen in the presence of BPG?
What is the main reason for the decrease in hemoglobin's affinity for oxygen in the presence of BPG?
Which technique is used to study protein structure in solutions and membranes?
Which technique is used to study protein structure in solutions and membranes?
What is the consequence of heat-induced denaturation of proteins?
What is the consequence of heat-induced denaturation of proteins?
What is the role of molecular chaperones in protein folding?
What is the role of molecular chaperones in protein folding?
What is the cause of denaturation due to urea and guanidine?
What is the cause of denaturation due to urea and guanidine?
What is the location of hydrophobic residues in membrane proteins?
What is the location of hydrophobic residues in membrane proteins?
What is the effect of mercaptoethanol on protein structure?
What is the effect of mercaptoethanol on protein structure?
What is the result of errors in protein folding?
What is the result of errors in protein folding?
What is the main role of the hydrophobic effect in protein folding?
What is the main role of the hydrophobic effect in protein folding?
What is the strategy used by chaperones to guide misfolded regions back into place?
What is the strategy used by chaperones to guide misfolded regions back into place?
What is the primary reason for the disruption of an α-helix by proline?
What is the primary reason for the disruption of an α-helix by proline?
What is the characteristic of the side chains in a globular protein?
What is the characteristic of the side chains in a globular protein?
What is the effect of the proximity of several side chains of like charge on the α-helix structure?
What is the effect of the proximity of several side chains of like charge on the α-helix structure?
What is the characteristic of the polypeptide chain in a β-pleated sheet?
What is the characteristic of the polypeptide chain in a β-pleated sheet?
What is the role of hydrogen bonding in the formation of an α-helix?
What is the role of hydrogen bonding in the formation of an α-helix?
What is the primary function of hemoglobin in the blood?
What is the primary function of hemoglobin in the blood?
What is the effect of 2,3BPG on the oxygen binding behavior of hemoglobin?
What is the effect of 2,3BPG on the oxygen binding behavior of hemoglobin?
What is the characteristic of the quaternary structure of hemoglobin?
What is the characteristic of the quaternary structure of hemoglobin?
What is the primary difference between the oxygen binding behavior of myoglobin and hemoglobin?
What is the primary difference between the oxygen binding behavior of myoglobin and hemoglobin?
What is the characteristic of fibrous proteins?
What is the characteristic of fibrous proteins?
What is maintained by extensive H-bonding that involves components of the peptide bond in a protein?
What is maintained by extensive H-bonding that involves components of the peptide bond in a protein?
What is the direction of the H-bonds in an α-helix?
What is the direction of the H-bonds in an α-helix?
Which bonds in a protein have free rotation?
Which bonds in a protein have free rotation?
What type of structure is characterized by extended, flat sheets?
What type of structure is characterized by extended, flat sheets?
What is the sequence of amino acids in a polypeptide chain referred to as?
What is the sequence of amino acids in a polypeptide chain referred to as?
What is the characteristic of secondary structures in proteins?
What is the characteristic of secondary structures in proteins?
What is the direction of the hydrogen bonding in an α-helix?
What is the direction of the hydrogen bonding in an α-helix?
What type of protein structure involves local conformations maintained by extensive H-bonding?
What type of protein structure involves local conformations maintained by extensive H-bonding?
Which of the following is a characteristic of α-helices in proteins?
Which of the following is a characteristic of α-helices in proteins?
What is the role of hydrogen bonding in the formation of α-helices?
What is the role of hydrogen bonding in the formation of α-helices?
What is the primary cause of denaturation due to pH changes?
What is the primary cause of denaturation due to pH changes?
What is the role of molecular chaperones in protein folding?
What is the role of molecular chaperones in protein folding?
What is the effect of mercaptoethanol on protein structure?
What is the effect of mercaptoethanol on protein structure?
What is the characteristic of the molten globule state?
What is the characteristic of the molten globule state?
What is the primary reason for the presence of hydrophobic residues inside globular proteins?
What is the primary reason for the presence of hydrophobic residues inside globular proteins?
What is the effect of heat on protein structure?
What is the effect of heat on protein structure?
What is the role of cryo-electron microscopy in protein structure determination?
What is the role of cryo-electron microscopy in protein structure determination?
What is the primary cause of denaturation due to urea and guanidine?
What is the primary cause of denaturation due to urea and guanidine?
What is the characteristic of protein denaturation?
What is the characteristic of protein denaturation?
What is the strategy used by chaperones to guide misfolded regions back into place?
What is the strategy used by chaperones to guide misfolded regions back into place?
What is the approximate distance between each turn of an α-helix?
What is the approximate distance between each turn of an α-helix?
What is the main reason for the formation of a β-pleated sheet?
What is the main reason for the formation of a β-pleated sheet?
What is the characteristic of fibrous proteins?
What is the characteristic of fibrous proteins?
What is the term for the interaction between amino acid side chains in non-neighboring regions of the polypeptide chain?
What is the term for the interaction between amino acid side chains in non-neighboring regions of the polypeptide chain?
What is the function of hemoglobin in the lungs?
What is the function of hemoglobin in the lungs?
What is the effect of BPG on hemoglobin's affinity for oxygen?
What is the effect of BPG on hemoglobin's affinity for oxygen?
What is the characteristic of the side chains in a globular protein?
What is the characteristic of the side chains in a globular protein?
What is the term for the completely folded and compacted polypeptide chain?
What is the term for the completely folded and compacted polypeptide chain?
What is the role of proline in an α-helix?
What is the role of proline in an α-helix?
What is the characteristic of the oxygen-binding curve of hemoglobin?
What is the characteristic of the oxygen-binding curve of hemoglobin?
Study Notes
Protein Structure Fundamentals
- 1° structure of a protein refers to its linear amino acid sequence from the N-terminal to the C-terminal end.
- Local conformations in proteins are maintained by extensive hydrogen bonding, particularly in secondary structures.
- Free rotation occurs around the peptide bonds and the bonds involving the side chain, allowing flexibility.
α-Helices
- α-Helices consist of hydrogen bonds between the amide N-H group of one amino acid and the C=O group of another, typically four residues away.
- Each turn of an α-helix contains approximately 3.6 amino acids.
- The hydrogen bonds in α-helices run parallel to the helix axis.
- Proline introduces a bend in the α-helix because of its rigid structure and inability to adopt a helical conformation.
- The presence of like-charged side chains nearby may destabilize the α-helix due to repulsion.
β-Pleated Sheets
- β-Pleated sheets are characterized by extended, flat structures maintained by hydrogen bonding between strands.
- In β-sheets, hydrogen bonds can connect distant parts of the polypeptide chain, contributing to stability.
Protein Classes
- Globular proteins tend to have polar side chains on the exterior for interaction with the aqueous environment, while hydrophobic residues are tucked inside.
- Fibrous proteins typically provide structural support and have elongated shapes.
Hemoglobin and BPG Interaction
- Hemoglobin's primary function is gas transport, specifically oxygen delivery to tissues and CO2 transport from tissues back to the lungs.
- 2,3-BPG lowers hemoglobin's affinity for oxygen, facilitating oxygen release in tissues.
- Hemoglobin also exhibits the Bohr effect, which describes the change in oxygen binding in response to pH and CO2 concentration shifts.
Protein Denaturation
- Denaturation results from factors like heat, pH shifts, and chemical agents (urea, guanidine) that disrupt hydrogen bonding and protein structure.
- Heat-induced denaturation leads to unfolding, loss of function, and potential aggregation.
- Mercaptoethanol disrupts disulfide bonds, further altering protein conformation.
Role of Molecular Chaperones
- Chaperones assist protein folding by preventing misfolding and aggregation, guiding misfolded regions back into proper conformation.
- Chaperones can recognize and bind to exposed hydrophobic regions on nascent or misfolded proteins.
Structural Features and Techniques
- Cryo-electron microscopy aids in protein structure determination by providing high-resolution images of proteins in their native states.
- The molten globule state describes a partially folded state of proteins that retains some secondary structure but lacks a compact interior.
Summary of Key Characteristics
- Secondary structures, including α-helices and β-sheets, rely on hydrogen bonds and specific amino acid interactions for stability.
- The arrangement and characteristics of amino acid side chains contribute significantly to protein functionality and structure.
- The overall structure of proteins influences their biological activity, interaction with other molecules, and response to environmental changes.
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Description
Test your knowledge of protein structure, including the primary sequence of amino acids and secondary structures like alpha helices and beta sheets.
