a)T/FIt is not energetically favorable to form a peptide bond. b)In which direct

Question

a)T/FIt is not energetically favorable to form a peptide bond.
b)In which direction do the hydrogen bonds run in an alpha helix relative to the direction of the helix? Between which atoms do they form?
c)In an alpha helix, where are the R groups located?
d)What amino acid is a helix breaker?
e)In which direction do the hydrogen bonds form in a beta sheet relative to the direction of the strands?
f)Describe the H bonds in a parallel beta sheet? In an antiparallel beta sheet?
g)In a beta sheet, where are the R groups located?

Explanation / Answer

a) True. The peptide bonds in proteins are metastable, meaning that in the presence of water they will break spontaneously.
b) The hydrogen bonds run almost parallel to the helix. The hydrogen bonds form between the amino group of an amino acid and the carboxyl group of another amino acid 4 residues away. (N-> N+4 bonding)

c) The R groups point outwards, roughly towards the N terminus.

d) Proline is a helix breaker due to the circular nature of the R group.

e) In B sheets, the hydrogen bonds form perpendicular relative to the strands.

f) The hydrogen bonding between in the anti-parallel beta-sheet is better aligned than in the parallel. Hydrogen bonds are most stable with the O-H-N angle is 180 degrees. This can be achieved in the anti-parallel, but not in the parallel arrangement, in which the bonds are at a greater angle since the amino and carboxyl groups do not line up as well.

g) In the fully extended strand, successive side chains point straight up, then straight down, then straight up, etc.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.