How many of the following give only glucose on complete hydrolysis?
Maltose, Sucrose, Lactose, Starch, Cellulose, Glycogen
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 4
A carbohydrate gives only glucose on hydrolysis when all of its monosaccharide units are glucose. If even one unit is a different sugar (fructose, galactose), the product is a mixture. For starch or cellulose the hydrolysis is:
\( \displaystyle \ce{(C6H10O5)_n + nH2O} \xrightarrow[\text{393 K; 2-3 atm}]{\ce{H+}} \ce{nC6H12O6} \)
Only glucose:
Maltose (two α-D-glucose units)
Starch (a polymer of α-glucose: amylose and amylopectin)
Cellulose (a straight chain of β-D-glucose units)
Glycogen (the animal starch, broken down by enzymes to glucose)
Not only glucose:
Sucrose — gives glucose and fructose (one molecule of each).
Lactose — gives galactose and glucose (β-D-galactose and β-D-glucose).
Only glucose: maltose, starch, cellulose and glycogen = 4.
NCERT (2026-27 edition):
10.1.1 Classification of Carbohydrates – “…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.”
10.1.3 Disaccharides – “(iii) Lactose: …It is composed of β-D-galactose and β-D-glucose.”
10.1.4 Polysaccharides – “(i) Starch: …It is a polymer of α-glucose and consists of two components— Amylose and Amylopectin.” … “Cellulose is a straight chain polysaccharide composed only of β-D-glucose units…” … “(iii) Glycogen: …When the body needs glucose, enzymes break the glycogen down to glucose.”