Which of the following sugars does not undergo hydrolysis?
(A) Glucose
(B) Fructose
(C) Cane Sugar
(D) Lactose
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (B) only
Carbohydrates are classified by their behaviour on hydrolysis. A monosaccharide cannot be hydrolysed into a simpler polyhydroxy aldehyde or ketone. A disaccharide gives two monosaccharide units on hydrolysis, because its glycosidic linkage is broken by dilute acid or an enzyme.
(A) Glucose — Correct. It is a monosaccharide (an aldohexose), so it does not undergo hydrolysis.
(B) Fructose — Correct. It is a monosaccharide (a ketohexose), so it does not undergo hydrolysis.
(C) Cane Sugar — Incorrect. Cane sugar is sucrose, a disaccharide; it is hydrolysed to glucose and fructose.
\( \displaystyle \ce{C12H22O11 + H2O} \xrightarrow{\ce{H^+}} \ce{C6H12O6}\,(\text{glucose}) + \ce{C6H12O6}\,(\text{fructose}) \)
(D) Lactose — Incorrect. Lactose (milk sugar) is a disaccharide; it is hydrolysed to galactose and glucose.
\( \displaystyle \ce{C12H22O11 + H2O} \xrightarrow{\text{enzyme or }\ce{H^+}} \ce{C6H12O6}\,(\text{galactose}) + \ce{C6H12O6}\,(\text{glucose}) \)
NCERT (2026-27 edition):
Monosaccharides
Oligosaccharides – “Carbohydrates that yield two to ten monosaccharide units, on hydrolysis, are called oligosaccharides. They are further classified as disaccharides, trisaccharides, tetrasaccharides, etc., depending upon the number of monosaccharides, they provide on hydrolysis. Amongst these the most common are disaccharides. The two monosaccharide units obtained on hydrolysis of a disaccharide may be same or different. For example, one molecule of sucrose on hydrolysis gives one molecule of glucose and one molecule of fructose whereas maltose gives two molecules of only glucose.”