Question

The two functional groups characteristic of sugars are
A. Carbonyl and phosphate
B. Hydroxyl and methyl
C. Carbonyl and hydroxyl
D. Carbonyl and methyl

Answer 1

Hint: Sugars are the soluble carbohydrates and sugars are used in food. Sugars are mainly compounds of carbon, hydrogen and oxygen. Carbohydrates are divided into monosaccharides, oligosaccharides and polysaccharides. Large carbohydrates or biomacromolecules are known as polysaccharides.

Complete answer:
Carbonyl and hydroxyl are the two main functional groups of sugars. The carbonyl and hydroxyl group present in all sugars. They are the basic components of sugars. Sugars are basically a carbohydrate and they are polyhydroxy aldehyde, ketone and their derivatives.
> Monosaccharides: They are simple carbohydrates which cannot be hydrolysed into smaller components because they are the simplest forms of carbohydrates. They are also known as biomicromolecules. They are 3 to 7 carbon compounds, e.g., glucose, fructose and ribose.
> Oligosaccharides: They are small carbohydrates formed by the condensation of 2 to 9 molecules of monosaccharides. It is formed by the addition of the aldehyde or ketone group of one molecule and the alcohol group of other molecules, e.g., sucrose, maltose and lactose.
> Polysaccharides: They are the polymers or chains of monosaccharides. Each monosaccharide is linked by the glycosidic bond. Polysaccharides are of two types: Homopolysaccharides (glycogen) and Heteropolysaccharides (chitin). They are also known as macromolecules, e.g., starch and cellulose.

So the correct answer is option C.

Note: Reducing sugars: These sugars can reduce $C{u^{2 + }}$ ions to $C{u^ + }$ ions. These sugars were used to detect the presence of glucose in urine by Benedict's and Fehling’s test. This property is found in those sugars which have free aldehyde or ketone groups. All monosaccharides possess this ability.