What is the molecular weight of a protein?

Which of the following molecules is capable of forming a Zwitter ion?

What is the secondary structure of proteins composed of?

The $pK_a$ values for the three ionizable groups $X, Y$ and $Z$ of glutamic acid are $4.3, 9.7$ and $2.2$ respectively. The structure is $HO_2C-CH_2-CH_2-CH(NH_3^+)-CO_2H$. The isoelectric point $(pI)$ for this amino acid is:

$A$ dipeptide,$X$ on complete hydrolysis gives $Y$ and $Z$. $Y$ on treatment with aqueous $HNO_2$ produces lactic acid. On the other hand,$Z$ on heating gives the following cyclic molecule.
Based on the information given,the dipeptide $X$ is:

Which one of the following statements is correct?