Question

Lactose is made up of
(a) Glucose + galactose
(b) Glucose + fructose
(c) Glucose + glucose
(d) Glucose + mannose

Answer 1

Hint: Lactose is a polysaccharide that on hydrolysis gives two monosaccharides which are white, sweet in taste, crystalline, and soluble in water and contains 6 carbons.

Complete step by step answer:
The molecular formula of lactose $C_{12}{H}_{22}{O}_{11}$ . Lactase is the enzyme essential to the complete digestion of milk; it breaks down lactose a disaccharide to its constituent monosaccharides glucose and galactose which give milk its taste. In lactose D- Glucose and D- galactose are joined by a ß- 1,4- glycosidic linkage. Lactose is not as sweet as other sugars such as sucrose or monosaccharides glucose and fructose.
- Carbohydrates are the energy-providing compounds made up of carbon, hydrogen, and oxygen.
- Carbohydrates are the polyhydroxy aldehydes or ketones and hydrolysis gives aldehyde or ketones.
- Carbohydrate classification depends on the hydrolysis products.
- Monosaccharides that are simple carbohydrates and are not hydrolyzed further made up of single polyhydroxy aldehyde or ketone units like glucose.
- When 2 to 9 monosaccharides condense it forms oligosaccharides and the units are held by glycosidic bonds, for example, sucrose, lactose.
- Polysaccharides are those made up of more than 9 monosaccharides units or they are the polymers of monosaccharides, for example, starch which contains the mixture of amylose and amylopectin in 1:4 ratio.
- On the basis of reducing properties these are divided into reducing and non- reducing sugars.

Note:
- Starch is the stored food of plants while glycogen is the reserve food in animals.
- Fructose is the sweetest sugar while starch is not sweet.
- Lactose is known as milk sugar, maltose as malt sugar, and sucrose as cane sugar.
- Cellulose is the most abundant carbohydrate.