Questions and Answers
What characteristic prevents free rotation around the bond between the carbonyl carbon and the nitrogen of the peptide bond?
Rigidity and planarity
Which condition is required to non-enzymatically hydrolyze peptide bonds?
Prolonged exposure to a strong acid or base at elevated temperatures
What term is used to describe each component amino acid in a polypeptide?
Residue
What stabilizes an α-helix structure by extensive hydrogen bonding between the peptide-bond carbonyl oxygens and amide hydrogens?
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What type of secondary structure forms when two or more separate polypeptide chains are arranged in parallel or antiparallel to each other?
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What is the name of the linear sequence of linked amino acids in a protein?
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Why is understanding the primary structure of proteins important?
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What type of bond joins amino acids together in proteins?
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What results from the linkage of many amino acids through peptide bonds?
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What type of bond joins amino acids together in proteins?
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What is the name of the level of protein structure that involves the sequence of amino acids in a protein?
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What is the convention for naming the ends of a peptide chain?
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What condition results in proteins with abnormal amino acid sequences, causing improper folding and loss of normal function?
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What characteristic prevents free rotation around the bond between the carbonyl carbon and the nitrogen of the peptide bond?
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What is the convention for writing the free amino end (N-terminal) and the free carboxyl end (C-terminal) of a peptide chain?
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Which type of structure forms when two or more separate polypeptide chains are arranged in parallel or antiparallel to each other?
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What term is used to describe the portion of the amino acid remaining after the atoms of water are lost in the formation of the peptide bond?
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What is required to non-enzymatically hydrolyze peptide bonds?
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What type of bond has a partial double-bond character and is shorter than a single bond?
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Which structure is stabilized by extensive hydrogen bonding between the peptide-bond carbonyl oxygens and amide hydrogens?
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What is the term for the spiral structure consisting of a tightly packed, coiled polypeptide backbone core, with the side chains of the component amino acids extending outward?
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How many amino acids are contained in each turn of an α-helix?
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What type of secondary structure is formed by two or more separate polypeptide chains that are arranged in parallel or antiparallel to each other?
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What type of sheet appears 'pleated' due to the almost fully extended segments of polypeptide chains involved in hydrogen bonding?
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What characteristic prevents free rotation around the bond between the α-carbons in the polypeptide chain?
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What type of bond helps reverse the direction of a polypeptide chain, aiding in the formation of a compact, globular structure?
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Study Notes
Peptide Bond Characteristics
- The peptide bond between the carbonyl carbon and the nitrogen has a partial double-bond character, preventing free rotation around the bond.
Hydrolysis of Peptide Bonds
- High temperatures and acidic or basic conditions are required to non-enzymatically hydrolyze peptide bonds.
Amino Acid Components
- Each component amino acid in a polypeptide is referred to as a residue.
α-Helix Structure
- The α-helix structure is stabilized by extensive hydrogen bonding between the peptide-bond carbonyl oxygens and amide hydrogens.
- There are 3.6 amino acids in each turn of an α-helix.
Secondary Structure
- The secondary structure formed by two or more separate polypeptide chains arranged in parallel or antiparallel to each other is called a β-pleated sheet.
- The β-pleated sheet appears 'pleated' due to the almost fully extended segments of polypeptide chains involved in hydrogen bonding.
Protein Structure
- The linear sequence of linked amino acids in a protein is referred to as the primary structure.
- The primary structure is important because it determines the overall function of the protein.
- A polypeptide is the result of linking many amino acids together through peptide bonds.
###Bonding
- Amino acids are joined together in proteins through peptide bonds.
- The peptide bond has a partial double-bond character and is shorter than a single bond.
- Hydrogen bonds help reverse the direction of a polypeptide chain, aiding in the formation of a compact, globular structure.
Protein Nomenclature
- The convention for naming the ends of a peptide chain is N-terminal (amino end) and C-terminal (carboxyl end).
- The convention for writing the free amino end (N-terminal) and the free carboxyl end (C-terminal) of a peptide chain is to label the amino end with the prefix "N-" and the carboxyl end with the prefix "C-".
Abnormal Protein Structure
- Mutations that result in abnormal amino acid sequences can cause improper folding and loss of normal function.
Alpha-Carbons
- The bond between the α-carbons in the polypeptide chain has a partial double-bond character, preventing free rotation around the bond.
Residue
- The term "residue" is used to describe the portion of the amino acid remaining after the atoms of water are lost in the formation of the peptide bond.
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Description
Test your knowledge about protein structures with a focus on the primary, secondary, tertiary, and quaternary levels of organization. Understand how amino acids are joined together by peptide bonds to form unique three-dimensional shapes.
