Question

When lactose is digested, it yields two monosaccharides known as
(a) Glucose and glucose
(b) Maltose and glucose
(c) Glucose and fructose
(d) Glucose and galactose

Answer 1

Hint: When a disaccharide like lactose is digested by hydrolysis, it yields two monosaccharides. The first of the two is the most abundant monosaccharide. The second monomeric unit is often known as brain sugar.

Complete answer:
When lactose is digested it yields two monosaccharides. They are known as glucose and galactose.
Let's begin the explanation by understanding carbohydrates. Organic biomolecules that are abundantly distributed in animals and plants are called ‘carbohydrates.’ Carbohydrates are often referred to as saccharides (in Greek sakcharon means sugar). Based on the number of sugar units present carbohydrates are classified into four broad categories namely monosaccharides, oligosaccharides, and polysaccharides.

Additional Information: Classification of carbohydrates:
Monosaccharides: (mono=one) They contain a single unit of sugar. They are the simplest group of carbohydrates and are known as ‘simple sugars’. Some of the monosaccharides are glucose, fructose, and galactose.
Oligosaccharides: (oligo=few) Carbohydrates that contain two to ten monosaccharides that are liberated on hydrolysis are called oligosaccharides. Based on the number of sugar units present oligosaccharides are further classified into disaccharides trisaccharides etc.
Disaccharides: As the name suggests they contain two sugar units. Examples of disaccharides are maltose (malt sugar), lactose (milk sugar), and sucrose (cane sugar).
Now let's see what monomeric units these disaccharides are made up of.
-Lactose, when broken down by hydrolysis, gives rise to glucose and galactose.
-Sucrose when broken down gives rise to glucose and fructose.
-Maltose on hydrolysis gives two units of glucose.
They are given below:
$Lactose\quad \xrightarrow { Hydrolysis } \quad Glucose\quad +\quad Galactose\\ Sucrose\quad \xrightarrow { Hydrolysis } \quad Glucose\quad +\quad Fructose\\ Maltose\quad \xrightarrow { Hydrolysis } \quad Glucose\quad +\quad Glucose$

So, the correct answer is ‘Glucose and galactose.’

Note: -In human beings, glucose and glycogen forms of carbohydrates serve as an instant source of energy for physiological activity.
-Lactose is commonly called milk sugar.
-Maltose is also known as malt sugar.
-The other name for sucrose is cane sugar. It is the commonly used table sugar.