Assertion (A) All naturally occurring $\alpha$-aminoacids except glycine are optically active.
Reason $(R)$ Most naturally occurring amino acids have L-configuration.
Assertion (A) Deoxyribose, $\mathrm{C}_5 \mathrm{H}_{10} \mathrm{O}_4$ is not a carbohydrate.
Reason (R) Carbohydrates are hydrates of carbon so compounds which follow $\mathrm{C}_x\left(\mathrm{H}_2 \mathrm{O}\right)_y$ formula are carbohydrates.
Assertion (A) Glycine must be taken through diet. Reason (R) It is an essential amino acid.
Assertion (A) In presence of enzyme, substrate molecule can be attacked by the reagent effectively.
Reason (R) Active sites of enzymes hold the substrate molecule in a suitable position.
Write the reactions of D-glucose which can't be explained by its open chain structure. How can cyclic structure of glucose explain these reactions?
Chemical reactions of D-glucose which can't be explained by its open chain structure are
(i) Glucose does not give Schiff's test and does not produce hydrogensulphite addition product with $\mathrm{NaHSO}_3$, despite having aldehyde group
(ii) The pentaacetate of glucose does not react with hydroxylamine.
In actual, glucose exist in two different crystalline form $\alpha$ form and $\beta$ form. It was proposed that one of the OH groups may add to the - CHO group and form cyclic hemiacetal structure. Glucose forms a 6 membered pyranose structure.
Cyclic structure exist in equilibrium with open structure and can be represented as
Due to formation of cyclic structure of glucose CHO group of glucose remain no longer free due to which they do not show above given reactions.