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Questions and Answers
Which of the following statements about keratin is FALSE?
Which of the following statements about keratin is FALSE?
The structure of protofilaments in keratin is stabilized by:
The structure of protofilaments in keratin is stabilized by:
Which of the following is an example of a globular protein?
Which of the following is an example of a globular protein?
What is the main structural unit of collagen?
What is the main structural unit of collagen?
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What structural feature is NOT found in collagen?
What structural feature is NOT found in collagen?
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How does the structure of keratin contribute to its insolubility in water?
How does the structure of keratin contribute to its insolubility in water?
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Which of the following statements best describes the central dogma of protein folding?
Which of the following statements best describes the central dogma of protein folding?
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What type of bonding is primarily responsible for the stability of the α-helix structure in proteins?
What type of bonding is primarily responsible for the stability of the α-helix structure in proteins?
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In proteins, which structure is characterized by parallel and anti-parallel arrangements of chains forming a pleated sheet?
In proteins, which structure is characterized by parallel and anti-parallel arrangements of chains forming a pleated sheet?
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What is the average number of amino acids per peptide in an α-helix within a globular protein?
What is the average number of amino acids per peptide in an α-helix within a globular protein?
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What characteristic is common to both α-helices and β-structures in terms of bonding?
What characteristic is common to both α-helices and β-structures in terms of bonding?
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Which type of protein structure involves the interaction of two or more polypeptide chains?
Which type of protein structure involves the interaction of two or more polypeptide chains?
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In a typical globular protein, where would you expect to find hydrophobic amino acids?
In a typical globular protein, where would you expect to find hydrophobic amino acids?
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What percentage of a typical protein’s structure is comprised of α-helices on average?
What percentage of a typical protein’s structure is comprised of α-helices on average?
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Concanavalin A, known for binding carbohydrates, is primarily composed of which type of structure?
Concanavalin A, known for binding carbohydrates, is primarily composed of which type of structure?
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What is the primary function of myoglobin?
What is the primary function of myoglobin?
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How many amino acid residues does myoglobin contain?
How many amino acid residues does myoglobin contain?
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Which structure of hemoglobin has a higher affinity for oxygen?
Which structure of hemoglobin has a higher affinity for oxygen?
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What is the significance of the heme group in hemoglobin?
What is the significance of the heme group in hemoglobin?
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What happens to the iron ion in the T structure of hemoglobin?
What happens to the iron ion in the T structure of hemoglobin?
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Which amino acid residues are not typically found in the interior of myoglobin?
Which amino acid residues are not typically found in the interior of myoglobin?
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What structural feature do both myoglobin and hemoglobin share?
What structural feature do both myoglobin and hemoglobin share?
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How many polypeptide chains are present in hemoglobin?
How many polypeptide chains are present in hemoglobin?
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Flashcards
Alpha Helix
Alpha Helix
A coiled secondary structure in proteins formed by hydrogen bonds between peptide bonds.
Beta Structure
Beta Structure
A secondary structure in proteins that forms sheets through hydrogen bonding between peptide strands.
Parallel vs Anti-parallel
Parallel vs Anti-parallel
Two arrangements of beta strands; parallel strands run together, anti-parallel strands run in opposite directions.
Myoglobin
Myoglobin
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Concanavalin A
Concanavalin A
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Globular Protein
Globular Protein
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Quaternary Structure
Quaternary Structure
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Domains in Proteins
Domains in Proteins
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Heme Group
Heme Group
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Alpha Helices
Alpha Helices
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Hemoglobin
Hemoglobin
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Relaxed Structure (R)
Relaxed Structure (R)
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Tense Structure (T)
Tense Structure (T)
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Oxygen Binding Capacity
Oxygen Binding Capacity
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Iron Ion Function
Iron Ion Function
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Haemoglobin Structure
Haemoglobin Structure
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Central Dogma of Protein Folding
Central Dogma of Protein Folding
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Protein Folding Process
Protein Folding Process
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Molecular Chaperones
Molecular Chaperones
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Fibrous Protein Example
Fibrous Protein Example
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Collagen Structure
Collagen Structure
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Myoglobin Discovery
Myoglobin Discovery
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Hydrophobic Amino Acids in Keratin
Hydrophobic Amino Acids in Keratin
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Study Notes
Amino Acid & Protein 2
- Proteins have complex structures, with several levels of organization, impacting their function.
- Forces influencing protein structure include hydrogen bonds between peptide groups, hydrogen bonds between side chains, hydrophobic interactions, and disulfide bonds.
- The forces determining protein shapes are vital for its functions.
Secondary Structures
- Alpha-Helix: Hydrogen bonds connect amino acids in a coiled, right-handed helix; on average ~11 amino acids per turn; can be up to 53 amino acids.
- Beta-Sheet: Hydrogen bonds form between parallel or anti-parallel polypeptide chains; forming a pleated sheet structure. Generally, 2-15 amino acids per turn (average = ~6); anti-parallel is more common.
Tertiary Structures
- Proteins' 3-dimensional structure is determined by the arrangement of secondary structures, forming super-secondary structures or motifs.
- On average 27% are alpha helix and 23% are beta structures.
- Exceptions do exist; for example, Myoglobin and Hemoglobin are 75-80% alpha helix, whereas Concanavalin A is entirely beta.
- Typically, hydrophobic amino acids are found in interior regions of protein structures. Polar and charged amino acids are on the surface, allowing them to interact with water.
Quaternary Structures
- The fourth level of protein structure involves the interaction of multiple polypeptide chains to form a larger protein.
- Individual chains are called subunits (monomers).
- Subunits can be identical (homogeneous) or different (heterogeneous).
- Common arrangements include dimers, trimers, and tetramers.
Central Dogma of Protein Folding
- Protein folding is spontaneous, often starting with secondary structures.
- The primary sequence dictates the final tertiary structure.
- Proteins have molecular chaperones that assist folding, especially under stress.
The Structure of Selected Proteins
- Fibrous Proteins:
- Structural proteins, with high tensile strength; insoluble in water.
- Examples: Keratin (hair, nails), Collagen (connective tissue), Silk (spiders' webs).
- Globular Proteins:
- Typically spherical, with hydrophobic amino acids inward, and hydrophilic amino acids outward; making them soluble in water.
- Examples: Myoglobin (oxygen transport), Hemoglobin (oxygen transport), Enzymes, Hormones.
Keratin
- Major structural protein of hair, nails, and horns;
- Its basic structure is an alpha-helix. Two alpha-helices twist to form a coiled-coil. Protofilaments group to form microfibrils and then to macofibrils.
Collagen
- Most abundant protein in vertebrates, mostly found in connective tissue (ligaments, tendons, cartilage);
- Triple helix of three collagen polypeptides. Has a repeating glycine-proline-alanine sequence & left-handed helix.
Myoglobin
- Oxygen-carrying protein;
- Small size and easily crystallizes, making it suitable for x-ray crystallography studies.
- 75% of its amino acid sequence is in alpha helix arrangement, with compact structure, 8 segments.
- Contains prosthetic heme group for oxygen binding.
- Has about 153 amino acids
Hemoglobin
- Oxygen-carrying protein in red blood cells, transporting oxygen and carbon dioxide;
- Has 2 alpha and 2 beta chains (tetramer), each with a heme group.
- Has about 574 amino acids
- Nearly spherical, with hydrophobic core and hydrophilic surface.
- 7-8 helical segment, with a plane Fe2+ in the middle or a slightly moved out heme for T state.
Denaturing Proteins
- Bonds maintaining a protein's shape are broken by changes in temperature, pH, or salt concentration.
- Proteins become denatured, changing shape & losing function;
- Fibrous proteins lose structural strength; globular proteins become insoluble and inactive.
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Description
Explore the complex structures and functions of proteins, focusing on their levels of organization including secondary and tertiary structures. Learn about the forces such as hydrogen bonds and hydrophobic interactions that influence protein formation and stability.
