NCERT Book Class 12 Chemistry Chapter 10 Biomolecules

Unit

Objectives
10
Biomolecules
After studying this Unit, you will be
able to
• explain the characteristics of “It is the harmonious and synchronous progress of chemical
biomolecules like carbohydrates, reactions in body which leads to life”.
proteins and nucleic acids and
hormones;
• classify carbohydrates, proteins, A living system grows, sustains and reproduces itself.
nucleic acids and vitamins on the The most amazing thing about a living system is that it
basis of their structures; is composed of non-living atoms and molecules. The
• explain the difference between pursuit of knowledge of what goes on chemically within
DNA and RNA; a living system falls in the domain of biochemistry. Living
• describe the role of biomolecules systems are made up of various complex biomolecules
in biosystem. like carbohydrates, proteins, nucleic acids, lipids, etc.
Proteins and carbohydrates are essential constituents of
our food. These biomolecules interact with each other
and constitute the molecular logic of life processes. In
addition, some simple molecules like vitamins and
mineral salts also play an important role in the functions
of organisms. Structures and functions of some of these
biomolecules are discussed in this Unit.

10.1 Carbohydrates Carbohydrates are primarily produced by plants and form a very large
group of naturally occurring organic compounds. Some common
examples of carbohydrates are cane sugar, glucose, starch, etc. Most of
them have a general formula, Cx(H2O)y, and were considered as hydrates
of carbon from where the name carbohydrate was derived. For example,
the molecular formula of glucose (C6H12O6) fits into this general formula,
C6(H2O)6. But all the compounds which fit into this formula may not be
classified as carbohydrates. For example acetic acid (CH3COOH) fits into
this general formula, C2(H2O)2 but is not a carbohydrate. Similarly,
rhamnose, C6H12O5 is a carbohydrate but does not fit in this definition.
A large number of their reactions have shown that they contain specific
functional groups. Chemically, the carbohydrates may be defined as
optically active polyhydroxy aldehydes or ketones or the compounds
which produce such units on hydrolysis. Some of the carbohydrates,
which are sweet in taste, are also called sugars. The most common
sugar, used in our homes is named as sucrose whereas the sugar present