Which of the following acids behaves like a salt in aqueous solution?

Identify the amino acid which has $-NH_2$,$-CO_2H$ and $-CONH_2$ groups.

Accumulation of which of the following molecules in the muscles occurs as a result of vigorous exercise?

Which $\alpha$-amino acid can cross-link peptide chains?

The correct statements are:
$A$. Activation energy for enzyme catalysed hydrolysis of sucrose is lower than that of acid catalysed hydrolysis.
$B$. During denaturation, secondary and tertiary structures of a protein are destroyed but primary structure remains intact.
$C$. Nucleotides are joined together by phosphodiester linkage between $C_{3}$ and $C_{5}$ carbons of the pentose sugar.
$D$. Quaternary structure of proteins represents the spatial arrangement of two or more polypeptide chains.
Choose the correct answer from the options given below:

During the denaturation of proteins,which of these structures will remain intact?