Question 23M.3.SL.TZ2.6
| Date | May 2023 | Marks available | [Maximum mark: 5] | Reference code | 23M.3.SL.TZ2.6 |
| Level | SL | Paper | 3 | Time zone | TZ2 |
| Command term | Describe, Explain | Question number | 6 | Adapted from | N/A |
Proteins are large polymers of 2-amino acids.
Describe the interactions between amino acids occurring at the primary, secondary and tertiary levels within a protein.
| Structure Level | Interactions between amino acids |
| Primary | ........................................................... |
| Secondary | ........................................................... |
| Tertiary | ........................................................... |
[3]
| Structure Level | Interactions between amino acids |
| Primary | covalent bonding OR peptide bond OR amide bond ✓ |
| Secondary | hydrogen bonding ✓ |
| Tertiary | interactions between R groups/side chains OR ionic/electrostatic «attraction» OR hydrogen bonding OR hydrophobic interactions OR disulfide bridges OR London/dispersion/van der Waals/«instantaneous» induced dipole-induced dipole ✓ |
Do not accept “amino acid sequence” for M1.
Do not accept “alpha helix” OR “beta sheets” for M2.
Accept “covalent bonding” for M3.
Explain how paper chromatography can separate and identify mixtures of amino acids.
[2]
Any two of:
sample spotted on paper/stationary phase AND solvent moves up the paper
OR
continuous cycles of adsorption and desorption/dissolution
OR
analyte moves when in solvent AND does not move when on paper ✓
different/depends on attractions to mobile phase AND stationary phase/paper
OR
«amino acids» separated based on solubilities in/affinity to the two phases
OR
separated based on polarities/polar attractions/molar masses of «amino acids» ✓
developed with ninhydrin/reagent/locating agent
OR
become identified with UV «light» ✓
«amino acids» identified by Rf/retention factor «values»
OR
Rf/retention factors «values» compared with known samples ✓
