Question

Which of the following is not a monosaccharide?
A) Glucose
B) Fructose
C) Glyceraldehyde
D) Sucrose

Answer 1

Monosaccharides can be classified based on the number of carbon atoms and the functional group present in them. If it contains an aldehyde group then it will be known as aldose and if it contains a keto group then it is known as a ketose.

Complete Step By Step Answer:
To solve this problem first we will see what monosaccharide is. Monosaccharides are that carbohydrate that cannot be hydrolyzed further to give the simpler unit of polyhydroxy aldehyde or simple ketone. There are almost 20 monosaccharides known in nature. Glucose, fructose, ribose, etc are some common examples.
Now we will explain each option.
Glucose-
Glucose occurs freely as well as combined form in nature. Its molecular formula is ${C_6}{H_{12}}{O_6}$ . It is present in honey and sweet fruits like grapes. It can be prepared as follows:
${C_{12}}{H_{22}}{O_{11}} + {H_2}O{\text{ }}\underrightarrow {{H^ + }}{\text{ }}{{\text{C}}_6}{H_{12}}{O_6} + {C_6}{H_{12}}{O_6}$
From sucrose we get two molecules one is glucose and the other one is fructose. Glucose is aldohexose and is also known as dextrose. It is a monosaccharide. It is the most abundant organic compound on earth. It is the monomer of many large carbohydrates such as starch, cellulose.
Fructose-
Fructose molecular formula is also ${C_6}{H_{12}}{O_6}$ but it has a keto group so it is known as ketohexose. It is obtained with glucose by the hydrolysis process of sucrose. It is a natural monosaccharide. It is found in fruits, vegetables. It can be used as a sweetener in its pure form.
Glyceraldehyde-
Glyceraldehyde chemical formula is ${C_3}{H_6}{O_3}$ and it is known as triose monosaccharide.
Sucrose-
Sucrose chemical formula is ${C_{12}}{H_{22}}{O_{11}}$ . We know that disaccharides on hydrolysis with dil acid give two molecules of monosaccharides. Sucrose is a disaccharide.
${C_{12}}{H_{22}}{O_{11}} + {H_2}O{\text{ }}\underrightarrow {{H^ + }}{\text{ }}{{\text{C}}_6}{H_{12}}{O_6} + {C_6}{H_{12}}{O_6}$
Here in this reaction sucrose gives one molecule of glucose and one molecule of fructose.
So here in the above-given option, only sucrose is not a monosaccharide.
Hence the correct option is (D).

Note:
The number of carbon atoms Monosaccharides is also formed under the name:
It is clear from the given examples. Glyceraldehyde is known as a triose monosaccharide. Because it consists of carbon atoms. Glyceraldehyde is also a monosaccharide.