A tryptophan sample in a buffer of $\text{pH }5.9$ remains stationary during electrophoresis. Draw the ions produced by tryptophan at $\text{pH }1.0$ and at $\text{pH }5.9$.
Tryptophan can react with valine to make a dipeptide. Use the Data Booklet to sketch this dipeptide.
Complete the table to show the product structures and the reaction type for each separate reaction between serotonin and the four reagents: Na, excess $\text{Br}_2\text{(aq)}$, excess $\text{CH}_3\text{COCl}$, and excess $\text{H}_2$/Pt catalyst.
Serotonin is changed by enzymes in the liver into compound $M$.
Using the Data Booklet, suggest a way in which the infra-red spectrum of $M$ would be different from that of serotonin.
The proton NMR spectrum of $M$ dissolved in $\text{CDCl}_3$ contains eight peaks because the molecule has eight different kinds of proton. The proton NMR spectrum of $M$ dissolved in $\text{D}_2\text{O}$ was then measured. Predict how many peaks would appear in the proton NMR spectrum of $M$ in $\text{D}_2\text{O}$. Explain your answer.
Compound $M$ can undergo polymerisation under suitable conditions to give polymer $N$, as shown. Polymer $N$ is biodegradable, whereas polyethene is not. Explain why $N$ is biodegradable.