Question

The sugar present in milk is
A. Glucose
B. Lactose
C. Fructose
D. Sucrose

Answer 1

Hint: One of the major food components is carbohydrates. Carbohydrates are required by the body as it gives energy to the body to do work. Also, carbohydrates when broken down by enzymes of the body, it gives glucose. For the brain, the direct source of energy is glucose. Excess glucose can be stored in the body in the form of glycogen. Glycogen is broken down at the time of need to give glucose. Most of the foods that we eat contain carbohydrates. For example, our daily meal consists of rice which is a rich source of starch, a form of carbohydrate.

Complete answer:
Glucose: Incorrect Answer
It is a monosaccharide containing six carbons and an aldehyde group. Rice contains starch which is made of amylose and amylopectin. When acted upon salivary or intestinal amylase, it is broken down into its monomeric units, glucose. It naturally occurs in fruits as well as other parts of the plant.

 Lactose: Correct Answer
It is a disaccharide sugar made of one galactose and one glucose unit joined by β 1 - 4 linkages. Lactose sugar is an important component of milk making up to 2-8% by its weight. Young ones of mammals feed on their mother’s milk. The doctors advise breastfeeding infants as colostrum contains immunoglobulins that help to fight diseases.

Fructose: Incorrect Answer
It is a monosaccharide containing five carbons with a ketone group. As it is mostly present in fruits, it is also called fruit sugar. Fructose can be directly absorbed by the body into the bloodstream.

Sucrose: Incorrect Answer
Sucrose is a disaccharide made of one glucose and one fructose molecule. The glycosidic linkage joins C1 of α-glucose and C2 of β-fructose. It naturally occurs in plants from which table sugar is refined.

Hence, the correct answer is option (B).

Note: Lactose sugar is digested by the lactase enzyme in the intestines of our body. However, certain infants lack this enzyme and are unable to digest the milk sugar causing bloating and flatulence in them. Such a condition is called lactose intolerance. Affected infants are thus advised by doctors to feed on milk supplements that do not contain lactose.