Question 23M.3.SL.TZ1.7
| Date | May 2023 | Marks available | [Maximum mark: 6] | Reference code | 23M.3.SL.TZ1.7 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Describe, Determine, Predict, State | Question number | 7 | Adapted from | N/A |
The amino acids in a protein can be separated using paper chromatography. The Rf values using a solvent of butanol and ethanoic acid are given.
| Amino acid | Rf value |
| Lysine | 0.14 |
| Glutamic acid | 0.30 |
| Threonine | 0.35 |
| Tyrosine | 0.45 |
| Asparagine | 0.5 |
| Methionine | 0.55 |
| Valine | 0.61 |
| Tryptophan | 0.66 |
| Leucine | 0.73 |
[Source: BioTopics. n.d. Chromatography of amino acids. [online] Available at:
https://www.biotopics.co.uk/as/amino_acid_chromatography.html
[Accessed 20 May 2021]. Source adapted.]
The following diagram shows a chromatogram.
Determine the identity of the amino acid creating spot C by calculating the Rf value from the chromatogram.
Identity of spot C: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
[1]
Identity of spot C:
leucine ✓
Predict, referring to the structure of the amino acids, whether spot X on the chromatogram in part (a)(i) is more likely to be serine or phenylalanine. Use the table of Rf values and section 33 of the data booklet.
[2]
serine AND more polar «than phenylalanine»
OR
serine AND OH group «on side chain» ✓
hydrogen bonding/greater affinity with stationary phase
OR
less soluble/poor affinity in solvent/mobile phase ✓
M2 may be scored without M1.
One role of proteins in the body is to catalyse reactions. Describe how enzymes catalyse reactions in the body.
[2]
bind to substrate at active site ✓
«provide» alternative pathway with lower «activation» energy ✓
Must have idea of binding to substrate AND a specific active site for M1.
State one industrial use of enzymes.
[1]
additives to detergents/washing powders/liquids
OR
breakdown oil spills/industrial waste ✓
Accept other industrial use.
Do not accept non-industrial uses, such as pregnancy testing.
