Which functional group participates in disulphide bond formation in proteins?

The most important energy source in every living cell is $......$.

Choose the correct Zwitter ionic form for aspartic acid.

Within the list shown below,the correct pair of structures of alanine in $pH$ ranges $2-4$ and $9-11$ is:
$I$. $H_{3}N^{+}CH(CH_{3})COOH$
$II$. $H_{2}NCH(CH_{3})COO^{-}$
$III$. $H_{3}N^{+}CH(CH_{3})COO^{-}$
$IV$. $H_{2}NCH(CH_{3})COOH$

When $HNO_3$ is dropped into the palm and washed with water,it turns yellow. The above yellow colour is due to:

Which of the following statements correctly describes the migration aptitude of aspartic acid during electrophoresis?
$(pK_1 = 2.0, pK_2 = 3.90, pK_3 = 10.0)$
$HOOC-CH_2-CH(NH_2)-COOH$