Biomolecules

Sucrose on hydrolysis gives equimolar mixture of D-(+)-glucose and D-(-)-fructose. These two monosaccharides are held together by a glycosidic linkage between $\mathrm{C}$-1 of $\alpha$-glucose and $\mathrm{C}$-$2$ of $\beta$-fructose. Both, assertion and reason are true and reason is the correct explanation of the given assertion. Hence, option (a) is the correct.

In nature glucose exists in cyclic hemiacetal form and has no free $-$CHO group, thus does not give 2, 4-DNP test.

Therefore, assertion and reason both are correct and reason is the correct explanation of the given assertion.

Hence, option (a) is the correct.

The amino acids that are not synthesised in human body and must be obtained from our diet are essential amino acids. Tryptophan is an example of essential amino acids.

Therefore, both assertion and reason are incorrect.

On hydrolysis with dilute aqueous sulphuric acid, sucrose forms a equimolar mixture of $\mathrm{D}-(+)$-glucose and $\mathrm{D}$ - $(-)$-fructose. The reaction for the hydrolysis of sucrose is as follow

$\underset{\text { Sucrose }}{\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}}+\mathrm{H}_2 \mathrm{O}$ $\xrightarrow{\mathrm{H}_2 \mathrm{SO}_4}$ $\underset{\text { D-(+)-glucose }}{\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6}$ + $\underset{\text { D-(-)-glucose }}{\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6}$

Solution of sucrose is dextrorotatory (specific rotation $=+66.1^{\circ}$) but after hydrolysis gives dextrorotatory glucose and laevorotatory fructose. The solution of formed product is found to be laevorotatory (specific rotation $=-20.0^{\circ}$)