BIOLOGY
AMINO ACIDS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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planar, but rotates to three preferred dihedral dihedral angles.
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non-polar, but rotates to three preferred dihedral angles.
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non-polar, and fixed in a trans confirmation.
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planar, and usually found in a trans configuration.
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Detailed explanation-1: -The peptide bond is planar and has two states: trans, ≈ 180°, and cis, ≈ 0°. In the trans configuration, the two alpha carbon atoms of the connected amino acids are on the opposite sides of the peptide bond, whereas in cis configuration they are on the same side of the peptide bond.
Detailed explanation-2: -Peptide bonds have a planar, trans, configuration and undergo very little rotation or twisting around the amide bond that links the -amino nitrogen of one amino acid to the carbonyl carbon of the next (Figure 4-1).
Detailed explanation-3: -The peptide bond nearly always has the trans configuration since it is more favourable than cis, which is sometimes found to occur with proline residues.
Detailed explanation-4: -The cis/trans isomers are with the same amino acid residue content, but in different peptide bond configurations. For most peptide bonds, the trans configuration is favored about 1, 000 times more than the cis configuration.
Detailed explanation-5: -The peptide bond is a stable covalent bond and is said to be a rigid planar bond because it has a partial double bond character. The evidence that shows this partial double bond character is from the length of the bond. It is 0.13 Angstrom shorter than the C-N single bond yet not as short as a double bond.