In IIT JEE, WBJEE, UPSEE and other engineering entrance examination the chapter Bimolecules plays an important role. About 1-2 questions are being asked from this chapter. This article talks about important concept, formulae and previous year questions related to Bimolecules. The concept given in this article is in concise form and can be used for revision before the examination.
They are the organic molecules that are involved in the maintenance and metabolic processes of living organisms. Thus, they build up the living system and are responsible for their growth and maintenance.
Some of the common biomolecules are:
• Nucleic acids
• ATP molecules
On the basis of hydrolysis, carbohydrates are classified as follows:
Monosaccharide: These are the simpler carbohydrates which cannot be hydrolysed further to its constituent aldehyde or ketone.
For example glucose,fructose, galactose etc.
Disaccharides: It is a sugar which can be hydrolysed into two monosaccharides.
For example sucrose, lactose, maltose.
Polysaccharides: These are carbohydrates which on hydrolysis yield many monosaccharide units.
For example starch, cellulose, glycogen, gums, etc.
Monosaccharides and oligosaccharides are crystalline solids, soluble in water and sweet in taste. These are called sugars. Polysaccharides are amorphous, insoluble in water and tasteless. These are called non-sugars.
D and L configuration of Sugar:
For defining D and L configuration of sugar the compound glyceraldehydes, HOCH2CH(OH)CHO was chosen as the standard.
Compounds that resembles D-glyceraldehyde at one terminal is known as D-sugar. Similarly, compound that resembles L-glyceraldehyde at one terminal is known as L-sugar.
Note: Natural sugar are D-sugar and synthetic sugar are L-sugar.
Cyclic Structure of Monosaccharides:
Some monosaccharides adopt cyclic structures. This conversion occurs because of the ability of aldehydes and ketones to react with alcohols:
Some questions are given below to test your knowledge.
Q1. Classify the following into monosaccharides and disaccharides.
Ribose, 2-deoxyribose, maltose, galactose, fructose and lactose
Ribose, 2-deoxyribose, galactose, fructose
Q2. Natural sugar is:
(c) Either D or L sugar
(d) None of these
Natural sugar is D-sugar while synthetic sugar is L-sugar.