Question 20N.3.sl.TZ0.a(ii)
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.3.sl.TZ0.a(ii) |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Deduce | Question number | a(ii) | Adapted from | N/A |
Proteins are polymers of amino acids.
The mixture is composed of glycine, , and isoleucine, . Their structures can be found in section 33 of the data booklet.
Deduce, referring to relative affinities and , the identity of A1.
[2]
Ile AND larger Rf ✔
more soluble in non-polar solvent «mobile phase»
OR
not as attracted to polar «stationary» phase ✔
Only award M2 if Ile is identified in M1.
Not well answered. Many candidates referred to glycine even when they had obtained the correct Rf value in 5a. Answers referring to Molar mass and isoelectric point were quite common. Some candidates that identified Ile correctly lost the first mark as didn't make any reference to the Rf. There was a clear lack of understanding that the Rf value was related to polarity not molar mass.
