Carbohydrates: The naturally occurring polyhydroxy
aldehydes or ketones or
substances which yield such compounds on hydrolysis are called carbohydrates.
They are of two types, sugars and non-sugars.
Sugars: These are soluble in water, sweet in taste
and crystalline in nature. Example: Glucose, cane sugar.
Non-sugars or Polysaccharides: These are insoluble
in water, tasteless and amorphous in nature. Example: Starch, cellulose.
Monosaccharides: The smallest basic
units of carbohydrates which cannot be hydrolysed
further are called monosaccharides. Example:
Oligosaccharides: The carbohydrates which on hydrolysis give
definite number (2 to 10) of monosaccharides or
simple sugar units of the carbohydrate, per molecule are oligosaccharides.
Example: Sucrose, maltose.
Proteins: The naturally occurring nitrogen,
containing polymeric compounds of very high molecular weight, containing
recurring -CONH- group are called proteins.
Simple Proteins: The proteins which on hydrolysis give only a-amino acids are
called simple proteins. Example: Egg, albumin, globulin.
Conjugated Proteins: The proteins which
on hydrolysis gives a-amino acids and some non-protein compounds are called
conjugated proteins. Example: Haemoglobin, casein
Derived Proteins: The proteins which are formed by the
treatment of some chemicals or heat on natural proteins are called derived
proteins. Example: Polypeptides.
Peptide Linkage: The recurring (-CONH-) linkage in protein
is known as peptide linkage.
Biuret Test: This test is for the
proteins containing peptide linkage in their molecule. A drop of aq. CuSO4 solution is added to the hydrolysed protein solution when a reddish violet colour develops.
Millon's Test: This test is for
those proteins which contain phenolic -OH group.
When a protein solution is warmed with Millon's
reagent (mercurous nitrate + mercuric nitrate in dil. HNO3) a white precipitate is formed which
turns red on heating.
Fats and Oils: They are the esters of trihydroxy
alcohol, glycerol and long chain carboxylic acid.
Saponification: The alkaline
hydrolysis of an oil or a fat resulting in the
formation of glycerol and soap is called saponification.
Hydrogenation: The reaction of hydrogen gas with an oil in the presence of a catalyst, like nickel, to give
a saturated solid fat is called hydrogenation.