Biomolecules

14.15

Hydrolysis is the process of using water to break down a molecule into two parts. It is usually a type of decomposition reaction where one reactant is water, where water is used to break chemical bonds in the other reactant. It can be considered as reverse of a condensation reaction.

The general formula of a hydrolysis reaction is:

XY + H₂O → XH + YOH

(i) On hydrolysis with dilute acids, sucrose yields an equimolecular mixture of α –D glucose and β–D- fructose.

(ii) The hydrolysis of lactose gives β–D-galactose and β–D-glucose as final products.

14.14

Glycogen is a polysaccharide-type of carbohydrate. In animals, carbohydrates are stored as glycogen.

But starch is a carbohydrate which consists of two components –amylase (15 -20 %) and amylopectin (80 – 85%). However, glycogen is also like amylopectin but branching will take place after every 5 to 6 glucose unit. Also, glycogen is highly branched.

14.13 

The condensation of the hydroxyl group of two monosaccharides to form a link between them is called glycosidic linkage. In other words, it refers to linkage developed between two different monosaccharide units through an oxygen atom by the loss of a water molecule. For example, in a sucrose molecule, two monosaccharide units, α-glucose and β–fructose, are joined together by a glycosidic linkage.

14.12 

i. Ribose, 2-deoxyribose, galactose, and fructose are

Monosaccharides are the simplest units of carbohydrates which cannot be hydrolyzed into simpler compounds.

ii. Maltose and lactose are

A disaccharide is a carbohydrate that is formed when two monosaccharides are joined together and a molecule of water is removed from the structure. Lactose is a disaccharide formed from the combination of galactose and glucose.

14.10 

All those carbohydrates which reduce Fehling's solution to red precipitate of Cu₂O or Tollen's reagent to metallic Ag is called reducing sugars. All monosaccharides (both aldoses and ketoses) and disaccharides except Sucrose are reducing sugars.

14.8

A DNA is a double-stranded molecule (two polynucleotide chains whose nitrogenous bases are connected by hydrogen bonds).

In this molecule pairing or connection of bases occurs. Adenine always pairs with thymine, while cytosine always pairs with guanine.

So when DNA is hydrolyzed the amount of adenine produced is exactly equal to the amount of thymine produced, similarly, the amount of cytosine produced is equal to that of guanine.

But as given when RNA is hydrolyzed, there is no relationship between the quantities of different bases obtained. This suggests that RNA is a single-stranded molecule.

14.7

When a nucleotide from DNA containing thymine is hydrolyzed β-D-2 deoxyribose and phosphoric acid are obtained.

14.6

Vitamin C (ascorbic acid due to extensive –H bonding with water due to the presence of –OH group) is a water-soluble vitamin in contrast to vitamin A, D, E and K which are fat soluble. Also, humans cannot synthesize it due to the lack of specific enzyme and it is rapidly absorbed from the intestine.

Because it is water-soluble, it is not stored in our body to a significant amount but is readily excreted in the urine.