The isoelectric point of lysine is 9.47. In the boxes below, draw the structure of lysine at each stated pH: lysine at pH $7.00$, lysine at pH $9.47$ and lysine at pH $12.00$.
Ethanoic acid is treated with $\text{PCl}_5$ to form product D. When D is added to tyrosine, two different isomeric products, E and F, are produced. E contains an ester linkage, whereas F does not. Draw the structures of D, E and F in the boxes below.
Complete Table 9.1 by sketching the structure of the organic product formed when tyrosine reacts with each named reagent. Ignore the directing influence of the $-\text{CH}_2\text{CHNH}_2\text{COOH}$ substituent.
A mixture of tyrosine and lysine can be separated by thin-layer chromatography. Under suitable conditions, the $R_f$ value of lysine is $0.14$ and the $R_f$ value of tyrosine is $0.45$. Explain what is meant by $R_f$ value.
Suggest a reason for the difference in $R_f$ values.