18 Questions
Which type of amino acid is most likely to disrupt the α-helix structure due to impossible bond rotation?
Proline
In an α-helix, which amino acids are considered strong helix formers?
Alanine and Leucine
Which type of amino acid is known to have a positive charge on its side chain?
Lysine
How does the sequence of amino acids affect the stability of an α-helix?
It affects the formation of hydrogen bonds within the helix
Which feature of the peptide bond contributes to the large macroscopic dipole moment of the α-helix?
The amide group having a negative charge
Why are peptide bonds aligned roughly parallel with the helical axis in an α-helix?
To maximize hydrogen bonding potential
What type of structure is formed by hydrogen bonds between the backbone amides in different strands of a β sheet?
Sheet
Which type of β sheet has strands that are oriented in the same direction?
Parallel sheet
What creates a pleated sheet-like structure in a β sheet?
Tetrahedral geometry of the α carbon
In antiparallel β sheets, how are the H-bonded strands oriented?
In opposite directions
What type of interactions are called sheets in β structures?
Hydrogen bonds
How do the hydrogen bonds between strands in parallel β sheets differ from antiparallel β sheets?
They are linear in parallel sheets and bent in antiparallel sheets.
Which factor contributes to peptide bonds being less reactive compared to esters?
Rigidity and stability
Why is rotation around the peptide bond not permitted?
Resonance structure
In a fully extended polypeptide, what are the angles for rotation around the α carbon—amide nitrogen bond and the α carbon—carbonyl carbon bond?
(180°, 180°)
What determines the secondary structure of a protein?
Organization around the peptide bond and identity of the R groups
What is the energy change (ΔGº') for peptide bond hydrolysis?
-10 kJ/mol
What defines oligopeptides compared to polypeptides?
Number of residues
Test your knowledge on how resonance affects peptide bonds, making them less reactive and rigid. Explore the angles around the alpha carbon and understand the restricted rotations in peptide structures.
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