$(1)$ Oxidation of glucose with bromine water gives glutamic acid
$(2)$ The two six-membered cyclic hemiacetal forms of $D-(+)$-glucose ard called anomers
$(3)$ Hydrolysis of sucrose gives dextrorotatory glucose and laevorotatory fructose
$(4)$ Monosaccharides cannot be hydrolysed to give polyhydroxy aldehydes and ketones
$\begin{matrix}
\underset{X}{\mathop{H}}{{O}_{2}}C-C{{H}_{2}}-CH-C{{O}_{2}}\underset{Z}{\mathop{H}}\, \\
\,\,\,\,\,\,\,\,\,\,\,| \\
\,\,\,\,\,\,\,\,\,\,\,\,\,+N{{H}_{3}} \\
\end{matrix}$
The isoelectric point for the amino acid is
If the absolute values of the net charge of the peptide at $pH =2, pH =6$, and $pH =11$ are $\left| z _1\right|,\left| z _2\right|$ and $\left|z_3\right|$, respectively, then what is $\left|z_1\right|+\left|z_2\right|+\left|z_3\right|$ ?