Question

Pentoses and hexoses are common :

• A. monosaccharides
• B. disaccharides
• C. polysaccharides
• D. oligosaccharides

Answer 1

Answer: (A)

Carbohydrates are compound of carbon, hydrogen and oxygen where hydrogen and oxygen occur in the ratio of $2:1$ and general formula is $C_n{H}_{2n}{O}_n$. They are of-
(i) Monosaccharides are monomer sugars which cannot be hydrolysed further into smaller units e.g., trioses, tetroses, pentoses (ribulose), hexoses (fructose).
Pentose sugars like ribose, deoxyribose are monosaccharides which has $5$ carbons.
Hexose sugar like glucose, fructose are monosaccharides which has $6$ carbons.
(ii) Disaccharides are carbohydrates made up of two monomeric units. e.g.,
Sucrose $=1$ glucose $+1$ fructose
Lactose $=1$ glucose $+1$ galactose
iii) Oligosaccharides are made up of $3-9$ monomeric units e.g., raffinose.
(iv) Polysaccharides are carbohydrates made up of more than $9$ monomeric units e.g., starch, glycogen.