Question

Lactose is composed of

• A. Glucose$+$Galactose
• B. Glucose$+$Fructose
• C. Glucose $+$Glucose
• D. Glucose $+$Manose

Answer 1

The correct option is A

Glucose$+$Galactose

The explanation for the correct option:

Option (A): Glucose$+$Galactose

1. Lactose is a disaccharide that breaks down into two saccharides, glucose and galactose on hydrolysis.
2. Both saccharides are joined by a beta glycosidic link.
3. It is a natural sugar found in milk in amounts ranging from 2 to 8%.
4. Lactose is a reducing sugar because it contains one free hemiacetal hydroxide.
5. Hence, it is the correct option.

The explanation for incorrect option(s):

Option (B) Glucose $+$Fructose

1. Sucrose is a disaccharide sugar consisting of subunits of glucose and fructose.
2. It is the main component of white sugar and is produced naturally in plants.
3. Hence, it is an incorrect option.

Option: (C) Glucose $+$ Glucose

1. Maltose is made by joining two glucose molecules together.
2. Maltose is a sugar that is generated when cereal grains germinate and is necessary for the fermentation of alcohol.
3. Hence, it is an incorrect option.

Option (D): Glucose$+$Manose

1. Mannose is a sugar monomer from the aldohexose sugar family.
2. It is a $\mathrm{C}-2$ epimer of glucose
3. Hence, it is an incorrect option.

Therefore, lactose is composed of glucose and galactose.

Hence, option (A) is correct answer.