Activation energy for the acid catalysed hydrolysis of sucrose is 6.22 kJ $\mathrm{mol}^{-1}$, while the activation energy is only $2.15 \mathrm{~kJ} \mathrm{~mol}^{-1}$ when hydrolysis is catalysed by the enzyme sucrase. Explain.
Enzymes, the biocatalysts reduce the magnitude of activation energy by providing alternative path. In the hydrolysis of sucrose, the enzyme sucrase reduces the activation energy from $6.22 \mathrm{~kJ} \mathrm{~mol}^{-1}$ to $2.15 \mathrm{~kJ} \mathrm{~mol}^{-1}$.
How do you explain the presence of an aldehydic group in a glucose molecule?
Glucose on reaction with bromine water produces gluconic acid. This indicates the presence of CHO group.
Which moieties of nucleosides are involved in the formation of phosphodiester linkages present in dinucleotides? What does the word diester in the name of linkage indicate? Which acid is involved in the formation of this linkage?
(i) $5^{\prime}$ and $3^{\prime}$ carbon atoms of pentose sugar.
(ii) Most probably the resemblance of with 2 ester $(-\mathrm{COO})^{2-}$ groups joined together.
(iii) Phosphoric acid $\left(\mathrm{H}_3 \mathrm{PO}_4\right)$.
Nucleosides are joined together by phosphodiester linkage between $5^{\prime}$ and $3^{\prime}$ carbon atoms of pentose sugar and a dinucleotide with phosphoric acid $\left(\mathrm{CH}_3 \mathrm{PO}_4\right)$ is formed
What are glycosidic linkages? In which type of biomolecules are they present?
Linkage between two monosaccharides due to oxide linkage formed by the loss of a water molecule, is known as glycosidic linkage as shown below
Which monosaccharide units are present in starch, cellulose and glucose and which linkages link these units?
Monosaccharides units present in starch, cellulose and glucose can be determined by knowing the product of their hydrolysis.
(i) Starch is a polysaccharide of $\alpha$-glucose in which two types of linkage are observed i.e., $\mathrm{C}_1-\mathrm{C}_6$ and $\mathrm{C}_1-\mathrm{C}_4$ glycosidic linkage.
(ii) Cellulose is a straight chain polysaccharide of $\beta$-D glucose in which glucose are linked together by $\mathrm{C}_1-\mathrm{C}_4$ glycosidic linkage.
(iii) Glucose is a monosaccharide.