Question 19M.3.hl.TZ2.9a(ii)
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.3.hl.TZ2.9a(ii) |
| Level | hl | Paper | 3 | Time zone | TZ2 |
| Command term | Compare and contrast | Question number | a(ii) | Adapted from | N/A |
Proteins have structural or enzyme functions.
Compare and contrast the bonding responsible for the two secondary structures.
One similarity:
One difference:
[2]
One similarity:
hydrogen bonding
OR
attractions between C=O and N–H «on main chain» [✔]
One difference:
α-helix has hydrogen bonds between amino acid residues that are closer than β-pleated sheet
OR
H-bonds in α-helix parallel to helix axis AND perpendicular to sheet in β-pleated sheet
OR
α-helix has one strand AND β-pleated sheet has two «or more» strands
OR
α-helix is more elastic «since H-bonds can be broken easily» AND β-pleated sheet is less elastic «since H-bonds are difficult to break» [✔]
Note: Accept a diagram which shows hydrogen bonding between O of C=O and H of NH groups for M1.
Accept “between carbonyl/amido/amide/carboxamide” but not “between amino/amine” for M1.
Almost all the candidate’s stated hydrogen bonding as the similarity between the 2 types of secondary structures but lost marks on the difference between them.
