Amino acids are the building blocks of

Which of the following is a condensation polymer?

Which compound can exist in a dipolar (zwitter ion) state?

For $\alpha$-amino acids having the structure $R-CH(NH_2)-CO_2H$,which of the following statements are true?
$(a)$ Water solubility is maximum at a $pH$ when concentrations of anions and cations are equal.
$(b)$ They give ninhydrin test.
$(c)$ On reacting with nitrous acid,they give off $N_2$.

Which functional group participates in disulphide bond formation in proteins?

Which of the following molecules forms a Zwitter ion?