Glucose and fructose are both reducing sugars. Why is sucorse regarded as a non-reducing sugar?

(i) Name the type of linkages responsible for the formation of primary and secondary structures of proteins.

(ii) On electrolysis in acidic solution, $\alpha$-amino acids migrate towards cathode while in alkaline medium, they migrate towards anode. Explain.

(iii) What are essential and non-essential amino acids. Give two example of each.

Compound $\left(\mathrm{A}\right)$, ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$, is oxidized by bromine water into a monobasic acid and also reduces Tollen's reagent and Fehling's solution. It also responds to the following reactions. Identify the compound $\left(\mathrm{A}\right)$.