Q8 - Identifying Amino Acids from Peptide Mass Data
A scientist has isolated five different peptides (1 to 5) containing five amino acids (named A, B, C, D, E). He determined the mass and the sequence of each peptide. The data which he obtained is shown on the table below.
| Peptide | Amino Acids Sequence | Mass (Da) |
|---|---|---|
| 1 | BCDACCDEDCB | 966 |
| 2 | ABBCAEEDECB | 1099 |
| 3 | BACDAEAEECA | 1357 |
| 4 | CACADBACAEB | 1279 |
| 5 | EDDCABBCCEE | 1014 |
The mass of individual amino acids are shown in the table below (in Da; note: the mass of a water molecule is 18 Da, subtracted once per peptide bond during formation).
| Amino acid | Mass (Da) | Amino acid | Mass (Da) |
|---|---|---|---|
| Alanine | 89 | Leucine | 131 |
| Arginine | 174 | Lysine | 146 |
| Asparagine | 132 | Methionine | 149 |
| Aspartic Acid | 133 | Phenylalanine | 165 |
| Cysteine | 121 | Proline | 115 |
| Glutamic Acid | 147 | Serine | 105 |
| Glutamine | 146 | Threonine | 119 |
| Glycine | 75 | Tryptophan | 204 |
| Histidine | 155 | Tyrosine | 181 |
| Isoleucine | 131 | Valine | 117 |
Using the information and data, determine which of the statements are true or which are false.
A. Amino acid named C is serine
B. Amino acid named A is tyrosine
C. Amino acid named E is cysteine
D. Amino acid named B is glycine
Question reproduced from IBO 2016, Theoretical Paper A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)