Why is the peptide bond planar? Select one: a. Bulky side chains prevent free ro

Question

Why is the peptide bond planar?

Select one:

a. Bulky side chains prevent free rotation around the bond.

b. It exhibits partial double-bond character, preventing rotation.

c. Hydrogen bonding between the NH and C=O groups limits movement.

d. None of the above.

e. All of the above.

Sickle-cell anemia is caused by:

a. the loss of the heme group because the proximal His is oxidized.

b. a decreased production of chains of hemoglobin.

c. a substitution of a Glu residue for a Phe residue at the 6 position.

d. a substitution of a Val residue for a Glu residue at the 6 position.

e. a substitution of Glu residue for His at the C-terminal of the chain.

Explanation / Answer

Answere :

Question 1 : The correct answere is (b) i.e. Peptide bonds are planner because it exhibits partial double-bond character, preventing rotation. The stability of the peptide bond bond is due to resonance of amide. Resonance keeps these four atoms -CO-NH- planar.

Question 2 : The correct answere is (d) i.e. sickle cell anemia is caused by a substitution of a Val residue for a Glu residue at the beta6 position. The sickle hemoglobin or HbS is caused by replacement of glutamic acid residue at the sixth postion og beta-globin chain by valine, which causes loss of two negative charges per one hemoglobin molecule.

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